Innovative Technologies in the Water and Waste Industries for the 21st Century
Proceedings of the 10th Annual CWWA Conference and Exhibition held in Grand Cayman, Cayman Islands 1-5 October 2001
Editors: Gelia Frederick-van Genderen and Martin B. Tedd
Water Authority – Cayman, P.O. Box 1104 GT, Grand Cayman, Cayman Islands
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Innovative Technologies in the Water and Waste Industries in the 21st Century
Local Organizing Committee G. Frederick-van Genderen (Chairperson) S. Carter (Deputy Chairperson) W. Warren (2nd.Deputy Chairperson) M. Ebanks J. Gadsby H. J. van Genderen G. Glidden S. Glidden T. Hill T. van Zanten
Conference Secretariat M. Martinez-Ebanks S. Carter J. Dixon T. Ebanks N. Diaz-Powery
Technical Paper Review Committee T. van Zanten (Chairperson) B. Mac Aree (Deputy Chairperson) C. Garbutt M. Tedd
ISBN 976-8110-00-7 (CD-Rom) All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or permitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without written permission from the publishers. The editors and publishers wish to make it clear that the data and opinions appearing in the Papers herein are the sole responsibility of the author(s) concerned. Consequently, the publisher and the respective employees accept no responsibility or liability whatsoever for the consequences of any such inaccurate or misleading data, opinion or statement.
Published by The Water Authority – Cayman, October 2001 ii
Innovative Technologies in the Water and Waste Industries in the 21st Century
Sponsoring Organizations
Argo American, Inc.
Consolidated Water
Cues
DesalCo
Experience and Expertise from
DesalCo
Ocean Conversion (Cayman) Limited
Southern Sewer Equipment
VacCon
Vermeer Caribbean
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Innovative Technologies in the Water and Waste Industries in the 21st Century
CONTENTS Foreword
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Opening Addresses Minister’s Feature Address: Honourable Edna Moyle, JP, Minister of Community Development,
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Women Affairs, Youth and Sports, Cayman Islands Government. Joint Message from Chairman of the Water Authority - Cayman Board, Mr Brainard Watler and
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Director of the Water Authority – Cayman, Dr Gelia Frederick-van Genderen Address from the President of the CWWA, Mr Errol Grimes
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Papers (From “Contents” page select author’s name to proceed direct to paper, from paper select title to return to contents page)
Water (Groundwater, Treatment, Distribution) UTAM S. MAHARAJ and TAWARI TOTA-MAHARAJ: High-Risk Groundwater Development Option for Small Island Developing States (SIDS)
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RAPHAEL EUDOVIQUE and LESTER ARNOLD: Evaluation of the Improved Water Supply Intake for Surface Water Sources
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E. LAWRENCE ADAMS and GRENVILLE S. MARSH: Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
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BRIAN JONES, HENDRIK-JAN VAN GENDEREN and TOM VAN ZANTEN: Well-Field Design for a Saltwater Reverse Osmosis Plant Located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
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HARRY PHILIPPEAUX: Water Reuse Criteria & Health
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Water (SCADA, GIS, GPS) R.. A. BISSON, R. B. HOAG, J.C. INGARI, U.S. MAHARAJ and L. JADOO: Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
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LAURENT DE VERTEUIL, ALFRED W. STAWICKI, ROLAND B. HOAG, ROBERT A. BISSON, JOSEPH C. INGARI, UTAM S. MAHARAJ and KERRY MULCHANSINGH: Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
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ROLAND B. HOAG Jr., CHRISTINE BOWMAN, PEDRO RESTROPO, RUDOLPH SANKAR, and UTAM S. MAHARAJ: Estimation of Groundwater Recharge in Trinidad Using Meteorological, Geographic Information Systems (GIS) and Watershed Modeling
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SCOTT F. BENDER, JEROME WALLACE and RICHARD J. MARTIN: Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
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RICHARD N. STALFORD and KEITH SHIRLEY: Charlotte Mecklenburg Utilities (CMUD) NC, USA, – Water Rehabilitation Integration with Geographic Information System, Case Study
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Water (Desalination) DONALD E. LINDEMAN and NEIL CALLAHAN: Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
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WILLIAM T. ANDREWS, DEREK WOOLLEY, MARINUS BARENDSEN and ANDREW P. HUTCHINSON: Seawater Desalination Plant at Sandy Lane, Barbados
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KENNETH CROWLEY and GERARD PEREIRA: The Cayman Islands’ 12 Year History of Municipal SWRO Plants Operating under Build-Own-Operate-Transfer Agreements
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ROBERT NICHOLSON: “The Modern Day Rain Maker” By Sea Solar Power
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SHAWN MEYER-STEELE, ANTONIA VON GOTTBERG and JOSE LUIS TALAVERA: New Seawater Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery and Cost Reduction”
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KEN GORING: Well-Field Development of the Barbados Water Authority Desalination Plant
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Wastewater JOANNE B. HUGHES: Coatings and Linings Providing Corrosion Protection and Structural Rehabilitation in the Wastewater Industry
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E. CRAIG JOWETT: Re-use of Treated Sewage in Canada for Irrigation and Toilet Flushing
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DUNCAN MARA: Low-Cost, High Performance Wastewater Treatment and Re-use for Public Health and Environmental Protection in the 21st Century
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B. D. CRITTENDEN, S. P. PERERA and R. MEHTA: Treatment of Factory Waste Oily Water
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L. ANDREA WILLIAMS-LEWIS: Manhole Rehabilitation Strategies: A Cost Effective Analysis
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B. J. LLOYD, K. GUGANESHARAJAH and C. A. VORKAS: A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
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JAMES W. HOTCHKIES: Application of a Membrane Bioreactor for Municipal Wastewater Re-use in The Florida Keys
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JOHN RUDOLPH, FRANK PEPE and STEVE ECKSTEIN: Wastewater Treatment Utilizing the Closed Loop Reactor - A New Twist to an Old Process
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WILLIAM A. TELLIARD: Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
316
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Innovative Technologies in the Water and Waste Industries in the 21st Century
MICHELLE WATTS: The Impact of Dunder Fertilization of Canefields on Surface Water Quality, St. Elizabeth, Jamaica
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E. CRAIG JOWETT and JOE ROGERS: Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
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RAYMOND L. PEAT: FAST Wastewater Treatment Systems with Nitrogen Reduction: An Affordable Solution to Decentralized Wastewater and Economic Development
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Solid Waste ERIC COPPET and VINCI ENVIRONMENT: Hazardous Wastes Management in French Islands
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VALERIE BEACH: Establishing Partnerships for Effective Solid Waste Management
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Management (Customer Issues, Human Resources) GLORIA GLIDDEN: Human Resources and Development (HRD) as a Value-Added Strategic Business Partner
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BILL MELENDEZ: Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
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RICHARD N. STALFORD: Hydraulic Modeling with GIS, Integration or Import. What are the Differences?
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ROS TAYLOR: Fast Track To The Top – Succession Planning for the Caribbean
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Quality Control THOMAS M. HARGY and JENNIFER L. CLANCY: UV Inactivation of Microorganisms in Water – A Review
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DONALD S. McCORQUODALE: Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
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ANTOINETTE JOHNSON: Drinking Water Quality Monitoring, The Cayman Islands Perspective
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JENNIFER L. CLANCY: E. Coli 0157:H7, A Deadly Emerging Waterborne Pathogen
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BRENDA MAC AREE: The Road to Laboratory Accreditation Using ISO/IEC 17025 – A Cayman Islands Case Study
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Registered Delegates
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Exhibitors
489
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Innovative Technologies in the Water and Waste Industries in the 21st Century
FOREWORD These proceedings record the papers presented at the 10th Caribbean Water and Wastewater Association (CWWA) Conference and Exhibition hosted by the Water Authority of the Cayman Islands. The conference was held at the Grand Cayman Marriott Beach Resort in the Cayman Islands, 1-5 October 2001. One of the major objectives of CWWA is to facilitate the growing desire for increased technical cooperation and network development in the Caribbean region as expressed in the Association’s Mission Statement: “To advance the science, practice and management of water supply and waste disposal for the benefit of Caribbean people through the development of human resources, public education and professionalism as well as promotion of appropriate technologies in the water and waste sector.” The CWWA Conference and Exhibition is an annual event that focuses on issues of key importance to the Water, Wastewater and Solid Waste Industries. Over the last ten years, the conference has evolved in terms of the quality and number of technical papers and exhibits, participants, and significance both within and outside the Caribbean region. The key industries of water, wastewater and solid waste present constant challenges to engineers and industry related professionals as they strive to provide efficient, effective and economical service to the general public in Caribbean nations that often are faced with limited resources. This conference offered an opportunity for dialogue and the exchange of innovative and current developments in technology and scientific research that is applicable to the region. This year’s conference theme “Innovative Technologies in the Water and Waste Industries for the 21st Century” proved to be very appropriate. Over 40 papers were presented by engineers, scientists, HR specialists, and other related professionals from the Caribbean, North America and Europe on a wide variety of topics ranging from innovative approaches to wastewater treatment, advances in desalination technology, use of GIS in the water and wastewater sector, challenges in human resources management, implementing automated meter reading, wellfield design, reuse of wastewater, rehabilitation technologies for wastewater collection systems, public health and environmental impacts and mitigation of the water and wastewater industry, quality control, and advances in solid waste management. Furthermore the International Desalination Association presented a round table discussion on the growth and acceptance of desalination in the Caribbean, the United States Environmental Protection Agency presented a seminar on developing regulations for pollutants in wastewater, and KCM Consulting Services presented a seminar on water distribution dilemmas. This conference took place in the wake of the World Trade Center and Pentagon bombings on 11th September 2001, events that evoked a lot of uncertainty about our way of life and the achievements of the democracies in the western world over the last 50 years. These events underlined that we all live in the global village as everyone was affected in some way. This conference also showed that the Caribbean is part of that global village, and it was heartening to see that despite the current uncertainty of the global situation, so many scientist, engineers, managers and business people representing the water, wastewater and solid waste sector from over twenty countries spent a week together in the Cayman Islands to participate in this great exchange of ideas and experiences. I thank all participants and the organizing committee for their support and encourage everyone to continue to make positive contributions to advance the water, wastewater and solid waste sector both within and outside the Caribbean. G.L. Frederick-van Genderen
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Minister’s Feature Address Honourable Edna Moyle, JP Ministry of Community Development, Women Affairs, Youth and Sports It gives me great pleasure to welcome you, the delegates of this regional water industry conference to our beautiful Cayman Islands. Water, one of the nature’s paradoxes, is both the supporter of life and bearer of death. In normal times, we cannot live without it, yet it can carry deadly diseases and in itself cause death during dangerous floods, hurricanes and mudslides. According to figures released by the World Health Organisation in 2000, around one sixth of the 6.1 billion people in the world lack access to potable sources of water, while 40% are without access to improved sanitation services. When one stops and thinks of how critical to our lives the supply of good quality water in sufficient quantities is, it makes one realize how vital the development of this infrastructure is in our heavily driven tourism industries in the Caribbean. Yet, it does not stop there, we must balance the water issue with management of our wastes. How we manage our solid and hazardous wastes impacts on our water supplies as poorly managed pollutants/contaminants from these can render our water sources unusable or very expensive to clean. Clearly, our potable water and waste management practices are irrevocably linked. Amazing, when you think that, every molecule of water we use continues to pass through the hydrological cycle and is reused again. The reliable supply of good quality water is important to me personally, as while growing up in the small, quiet, beautiful district of North Side I saw first hand the economic, environmental and social hardships that faced those in my community who did not have access to freshwater wells and springs. Many of us had to back water in buckets and ration what we had during the dry season, many of us had only pit latrines to use and of course, it was the women who had to carry the heavy loads. Although, economically we are 100% better off now than in those days, I look forward to the day the piped supplies reaches my North Side communities. Healthy, clean piped water to their door is already a reality for the Water Authority’s more than 8,000 customers. Furthermore, more than 90% of the Islands’ residents have access to piped water ‘city water’ through either our supplies or that of a private company (Cayman Water Company), which under Government franchise supplies all areas west of the Watler’s Road community. During my tenure as Minister responsible for the Water Authority, it is my sincere intention to support the extension of the Authority’s water distribution system so that within a reasonable period the entire population of these islands have available to them a reliable supply of good quality water. I read with interest the chosen theme of the conference and challenge each of you participating in the scientific research of new, re-worked and innovative technologies to keep in the forefront as one of your driving criteria, the cost of the technology. Not only financially, but also environmentally, weighing all aspects as you seek better, cheaper, more efficient ways of taking
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care of the business. When you work on these issues together - recognizing the integration and interrelationships - you really start to make progress. As I read the abstracts, I was impressed to see the wide range of topics covered. It shows that in relation to the water and waste issues facing us today that your organisation, CWWA, takes a holistic approach, from the highly technical scientific papers to those dealing with the make or break issue of “human resources”. My interest in women’s issues is well known here in Cayman and I was especially proud to count the names of over a dozen women either authoring, co-authoring and/or presenting papers including two from our own Water Authority staff. This conference, I understand will have the benefit of world-renowned scientists and leaders in their field from well-respected universities and consulting firms. Papers on solid waste and hazardous waste management are timely as well as are those on wastewater reuse and wastewater treatment. The paper dealing with ocean thermal energy conversion technology will be of great interest as it deals with utilizing the temperature differential in the ocean to produce electrical energy and freshwater. We have some deep waters just off the dropoff so if this works, we in Cayman should benefit with lower costs for electricity and water. Other papers deal with sophisticated ways to utilize our fresh and saline groundwater aquifers. With two roundtable discussions and a seminar, plus I understand that three commercial seminars were conducted yesterday, this conference certainly offers delegates every opportunity to share experiences, successes, failures and ideas for the common good and interest of all. The first roundtable discussion will look at the development of desalination in the Caribbean and I understand that the panelists are representatives from the largest desalination organisation in the world, the International Desalination Association. The second roundtable discussion will look at dilemmas faced by engineers and operators dealing with water distribution systems. The seminar on United States Environmental Protection Agency methods and regulations for pollutants in wastewater should be useful for countries reviewing or developing effluent discharge regulations. In Cayman, as in most of our Caribbean neighbours, our Governments are under pressure to balance the need for infrastructure development with other social services’ needs and the ever increasing cost of conducting the business of Government. And, in the midst of this, our big neighbour to the North appears to be on the verge of a slowdown in their economy, which of course, affects our more fragile economies. This means that in many of our countries, there is a great effort to streamline and seek innovative partnerships with the private sector and/or establishment of statutory corporations. As "big government" shrinks in many parts of the world, privatization spreads and as the old adage goes, "To whom much is given, much is expected”. With a more sophisticated and educated populace, public expectations can only grow. One such expectation is the public's demand for more accountability, or transparency, of business activity. In the very important business of water and waste management we have to give our commitment to increased accountability and transparency. Our customers demand it. New technologies are allowing us to connect directly with our customers and colleagues unlike ever before, our customers have access to more information than ever before. This is bringing incredible opportunities, many that we are only just beginning to recognize and utilise. It also brings challenges - public expectations and demands are changing.
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Here in Cayman, we have seen most of the 1990’s bring with it great economic development. Such that our two piped water suppliers have had to work hard to keep up with double digit growth on an annual basis. In fact water demand has doubled in the last six years, and the Authority’s customer base has just about doubled to over 8000 during the same period. Population growth in the Cayman Islands continues at a rapid pace fueled by the need for human resources. In fact, our 1999 census figures indicate that our population has grown by 50% in the last ten years. This creates challenges for supplying freshwater to the country as we lack major sources of freshwater to satisfy our needs. The reverse osmosis desalination process has been proven to be the solution for the Cayman Islands; this process is high tech, needs qualified personnel and is costly compared to those countries fortunate enough to have abundant rivers. With the accompanying growth in the tourist industry and subsequent construction boom, the pressure to extend piped water systems increased significantly. I am pleased to note, as Minister responsible for the Water Authority, that the two utilities continue to invest in extension of the water distribution system infrastructure. Another challenge facing the water and wastes industry is the competition and demand for water from the manufacturing and agricultural industries. I believe it is responsible policy to challenge these industries to be innovative and on the cutting edge of technology to find ways to reduce usage, conserve and reuse our precious water resources. The Water Authority has two major projects in development and nearing commencement. The Grand Cayman Wastewater Treatment Works and the new Red Gate reverse osmosis 3000 cubic metres per day water desalination plant. The Wastewater Treatment Works will replace the current treatment process of waste stabilization ponds which have reached design capacity and experienced operational performance deficiencies. Consequently, the Authority intends to construct a new treatment plant, a sequencing batch reactor (SBR), which will meet the island’s needs for wastewater treatment in the long term. This multi-million dollar project is expected to break ground in early 2002 and will take about 18 months to complete. The new reverse osmosis water production plant will increase the Authority’s production capacity to 11,000 cubic metres per day. And if demand continues as expected, the Authority will be doubling the capacity of the plant within 12 months after it is operational. Construction on this plant will be commencing shortly. I understand that at the Awards banquet, CWWA takes the opportunity to recognize persons in the Caribbean who have made a significant contribution to the water and wastes industry, generally through years of service. I would like to challenge CWWA to consider expanding the awards’ system to recognise and award innovative cost-effective technical solutions to the water industry problems and issues developed in our region or through scientific research in our region. In addition to that, why not include an award for young, Caribbean scientists under the age of twenty. I personally believe, that we adults must take every opportunity to encourage our youth and recognise their talents. These young, innovative, future-oriented and technically savvy young people are the ones who will take our places as the 21st Century progresses. I look forward to touring the exposition as the exhibits look very informative. I am pleased to note that the exhibit will be open to the general public on Thursday morning. I certainly
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encourage those of you who have an interest in the water and wastes industry to come by. It is encouraging to see the level of support that the corporate sponsors have given, again this is a partnership that is to be encouraged. As you network amongst each other over the next four days, I encourage you to take this opportunity to discuss and work on the challenging issues essential for our survival and development as young countries in the Caribbean region such as solving the common goals of water pollution prevention, environment sanitation, water supply reliability, efficient use of water and public health. At times, corporate decision makers may find it hard to understand and interpret the latest scientific research which is one of the reasons forums such as this are so important to bring all of you, the key players together. This year, in fact just last August at the Stockholm Water Symposium in Sweden, the theme of the symposium was “Building Bridges Through Dialogue”. Yes, we recognize we have differences, but as it is often said by great leaders, “united we stand divided we fall”. I wish you a productive and successful conference and an enjoyable stay in our beautiful Cayman Islands.
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Joint Message from the Chairman of the Water Authority-Cayman Board, Mr Brainard Watler and Director of the Water Authority-Cayman (Chairperson, Planning Committee) Dr Gelia Frederick-van Genderen On behalf of the Water Authority of the Cayman Islands’ Board of Directors and staff, it is my privilege to welcome you our esteemed colleagues in the water and waste industry to the Cayman Islands for this 10th CWWA Annual Conference & Exhibition. It is indeed an honour to be included among such a distinguished group of delegates as yourselves. A full decade has gone by since the inception of CWWA and it has earned the respect and recognition of other major regional and international organisations. The resulting relationships with PAHO, AIDIS, CEHI and EPA contribute to the further development of CWWA and members. We are honoured to have been chosen by CWWA to host this most important conference. This is the second time that the Water Authority has had the opportunity to host a regional conference for the water and wastes industries. Some of you may recall the last conference of CWWA’s predecessor, the Caribbean Water Engineers’ Conference that we hosted in 1991. We hope that you will find this conference a rewarding experience, renewing old friendships, establishing new ones and expanding your contacts. We encourage you to use this conference as your opportunity to develop and strengthen the positive relationships between our respective industries, our countries and suppliers. We are in pursuit, of what I believe is our common goal: clean, affordable water in sufficient quantities for our populations and best practice management of our wastes streams at the same time promoting economic prosperity. With over 40 technical papers and more than 30 exhibitors, together with overseas and local delegates, this conference promises to be very informative. We must extend our appreciation to our corporate sponsors whose support for this CWWA and this conference has been commendable and substantial.
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We are proud of the Water Authority staff and those on the various committees planning this conference. We run a tight organisation, not only financially but also in human resources so the members on the committees kept up their usual great work and took on this additional load. Many gave of their personal time at no extra cost to see this conference through. Again, I can only say thanks and I am sure it will be worth it when the conference is over. The organizing committee has done a lot of work to ensure that conference is well organized. If there is anything you need assistance with, do not hesitate to approach one of us. Again on behalf of the Chairman and Water Authority Board and staff, I welcome you to the Cayman Islands and this conference. We are especially pleased to see so many participants here today and we look forward to meeting many of you during the week ahead and at the social functions we have planned.
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Address from CWWA President Mr Errol Grimes
On behalf of the CWWA Executive and the members of the association, it gives me great pleasure to extend a very warm welcome to the participants, presenters and exhibitors at our 10th Annual Conference and Exhibition which is being held this year, in the beautiful Cayman Islands. The annual Conference is the major milestone in the CWWA calendar of events. This year’s theme, “Innovative Technologies in the Water and Waste Industry for the 21st century” bring into focus some of the new thinking in the Caribbean, which is guiding the way forward in the water and waste sector. The papers being presented bear testimony to the new direction. Desalination, for instance, is growing as an alternate to the traditional sources of water in the Caribbean. In Trinidad, the construction of one of the largest Reverse Osmosis desalination facilities in the world, to produce 24 IMGD, is in progress and nearing completion. There are also concerns about environmental degradation especially on some of our fragile island tourist economies. This emphasizes the need for effective wastewater and solid waste management. I want to congratulate the hard working conference planning committee here in the Cayman Islands, I am sure this experience has been a very interesting, possibly stressful at times but nevertheless a rewarding one. In recent years the annual CWWA conference has grown in leaps and bounds and its organization has become increasingly challenging. The CWWA strength is based on the active participation of its members. Its development also hinges on the growth of its membership. I want to implore members to actively participate in the three Technical Committees namely, Water, Wastewater and Solid Waste, established at last years conference in Trinidad and Tobago and also assist in expanding our membership. Our relationship with PAHO, AIDIS, CEHI, EPA and other international organizations is expanding. We are continuing to work closely with PAHO to develop our strategic plan, which is essential to our institutional development. The quality of the presentations at the Conference has been steadily improving. The proceedings for last year’s conference, for the first time, are now available on compact disc (CD). Our exhibitors deserve special mention, their continued support, among other things, has helped our conference event to grow. One again, I extend a warm welcome to you and wish you an informative, educational and enjoyable conference.
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PAPERS
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High-Risk Groundwater Development Option for Small Island Developing States (SIDS) by Utam S. Maharaj and Tawari Tota-Maharaj.* Water and Sewerage Authority, Trinidad Abstract A major water supply initiative within the republic of Trinidad & Tobago is the pursuit of new groundwater on the islands targeted in specific high demand areas. This strategy was not initially considered since to our knowledge all the existing groundwater within reach to our current demand areas, was exhausted. As far as the Government-run water authority was concerned there was no more known groundwater in close proximity to the demand that could be developed; all known aquifers were producing at their safe yields. The Republic, due to prior perception of limited available new groundwater was forced to focus its water source development on surface water sources, including sea-water desalination. This high dependence on surface water had put the supply of domestic and industrial water at severe risk due to low river flows during the dry seasons and high turbidity levels during the rainy seasons. Proponents of new geological concepts that have the promise of locating and developing new sources of groundwater utilizing state-of-the-art technology were challenged to initially develop 15 MGD for the island of Trinidad and 4 MGD for the island of Tobago. These sources, in the main, targeted the bedrock of the islands to tap the water from major fracture conduits underlying many traditional watersheds. Since our own position was that groundwater development was “high risk”, the contractors were engaged to carry out this project on a predominately “success-basis”. The results of these projects are to be presented. Both islands have shown potential for additional groundwater in the order of seven (7) times of what was originally estimated from prior studies and existing production. The proof of the new concepts was realized with the procurement of a large proportion of the contractually required amount of production capacity to date. The realization that substantial amounts of groundwater are available on both islands provides an attractive option to improve the quantity and reliability of the water supply. Groundwater development in already explored regions has an extremely high exploration and attendant financial risks that need to be managed. Consideration of these risks and how they were minimized will be presented in this paper. We have concluded convincingly that new groundwater sources from bedrock aquifers are superior to surface sources for potable water, from both reliability of supply and cost of development for SIDS.
*Presenter
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High-Risk Groundwater Development Option for Small Island Developing States (SIDS)
Introduction Small island developing states, often referred to as SIDS, are recognized as having extreme vulnerability to economic and environmental forces. Economically, they are very dependent on outside, larger economy markets and tend to be dependent upon few or even single commodities. Population and commercial development threaten limited natural resources, such as land, water, fisheries, coral reefs and beaches making them extremely prone to environmental forces including climate change and sea-level rise. The susceptibility to these factors is extremely high. Another vulnerability factor that is quickly emerging as having severe impacts on SIDS is the provision of safe drinking water. This current year (2001), when many Caribbean states had to severely ration water, emphasises this situation. In the case of Trinidad the island had experienced a 1:30 year drought in the northern part of the island where the major impounding reservoirs and surface water intakes exist. Tobago had experienced its worst drought in the 50-year history for which hydrological records are available. With further population increases, diversification of their economies and infrastructural development, the water supply demand situation will worsen. Water supply in small islands, with most of their population centers and industries situated along their coastlines are extremely vulnerable to the traditional development of surface water sources due to the increasing pollution from human activity and lack of reliability due to changing climate. As will be discussed in this paper, the reliability issue, using Trinidad and Tobago as an example, manifests itself in both the dry and wet seasons. Their small size, steep slopes and quick associated run-off, large coastal regions, important coastal development, tropical climate and volcanic origin generally characterize the islands of the Caribbean. A large proportion of their GDP is often based upon tourism and agriculture. Trinidad & Tobago The Republic of Trinidad and Tobago is an archipelagic state located at the southern end of the Caribbean island chain. The islands have a tropical climate of the monsoonal type. Rainfall that averages 86.6 inches, is seasonal with a wet season from June to December and a dry season from January to May. Temperatures range from 25 to 27 °C and humidity ranges between 50 to 100%. Trinidad’s landscape is characterised by steep mountains, undulating hills and plains. Tobago’s landscape is however, characterised by a highland area, which runs along the long axis of the island and a small coastal plain on the southwest tip. The islands are endowed with extremely varied coastlines, a fair share of wetlands and richly diverse flora and fauna. With respect to the demographics of the islands, the population is estimated at 1.25 million with an annual growth rate of 1.2 percent. Trinidad’s population is concentrated in urban
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High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
areas along the west coastal areas and at the foothills of its northerly located mountain range. Tobago’s population is concentrated in the southwest part of the island. Relative to the rest of the Caribbean islands, the country is highly industrialised with a petroleum-based economy and a small but rapidly growing tourism industry concentrated mainly in Tobago. Pollution is a problem that is on the rise throughout the country. The main water pollutants are: Ø Ø Ø Ø Ø
Urban, domestic, and industrial waste Solid and toxic agricultural products and waste Sediments, petrochemicals and oil spills from the oil and energy industries Waste from fishing vessels, ships, tourist facilities and yachts Siltation from land degradation, infrastructural development, agriculture and quarrying
Relative Abstractions MCM/Year
Ground Water 23%
Surface Water
Surface Water 77%
Groundwater
Figure 1: Relative Abstractions of Surface and Groundwater on the Islands The Republic’s water supply prior to several new projects was made up of 77% surface water sources and 23% groundwater sources. Due the tropical seasonal fluctuations of rainfall, the supply situation is often threatened in both the rainy and in the dry season. Major infrastructural development works within the catchments, the advent of substantial quarrying and the presence of poor agricultural practices results in high levels of siltation and other forms of pollution which seriously impact the surface water sources. All intakes and impounding reservoirs, from which pristine water was supplied in the past, often cannot now supply water of adequate quality for treatment during times of heavy rainfall. This paradoxical situation has led to several instances of low or no supply during heavy rainfall. On the other hand, extreme low-flow events during the dry season over the last few years, 3
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
combined with increasing demand within the catchments, are causing situations to develop which impact on the ability to supply to customers at the levels that they have grown accustomed to. Vulnerability of SIDS to SW Sources Over the last five (5) years, the Republic had embarked on major water related investments, including the upgrade of several of its water supply installations. Upgrades on surface water supply sources were designed to increase supply or improve reliability or both. Time lines of the monthly water production at several of the major installations, some of which have been upgraded were plotted to demonstrate the vulnerability of the water supply situation on both islands. The trend plots along with the plants rated capacities are shown in Figure 2 for the island of Trinidad. The largest water plant on this island, Caroni over the last five (5) years had produced at or above its rated capacity fairly consistently. Upgrade of this plant in mid2000 increased its water treatment capacity by 25%, obtaining the maximum production from this plant as shown in the Figure. It has now become susceptible to low flows due to limited precipitation within the catchment. The Navet plant has traditionally been somewhat susceptible to dry-season low flows with no wet season problems, while the NorthOropouche plant is susceptible to both turbidity spikes in the rainy season and low flows during the dry season. Figure 3 shows a similar situation for the plants in Tobago. Hillsborough reservoir shows an extreme dry-season vulnerability while the Courland and Richmond plants traditionally demonstrate wet season susceptibilities. The latter two (2) plants have recently been upgraded to increase wet-season reliabilities. While there is no question that these upgrades were essential to the solution of the water stresses facing the Republic, the reliability problems though significantly diminished are still present. Solving these problems require both putting additional water-into-supply to alleviate the low season stresses and upgrading surface water intakes to allow them to remove high levels of suspended solids. An alternative is to access new sources of reliable water. In this regard, the utility has commissioned the construction of a 24 million gallons per day buildown-operate desalination plant (located at Point Lisas) in central Trinidad to supply the needs of its major industrial customers. A more recent alternative that is being pursued is the development of new groundwater sources on both islands. All prior assessments of the geology and hydrogeology of the islands indicated that we were using all available groundwater in proximity to high demand areas. New technologies to identify new sources of groundwater within the islands’ bedrock were identified as possible means of developing a reliable source of water for the public water system. Without the in-house expertise and the expectation that all the readily available groundwater was already developed, such a project was considered extremely high risk.
4
High-Risk Groundwater Development Option for Small Island Developing States (SIDS) 400,000 C A R O N I P R O D U C T IO N G R A P H 1 9 95 - 2 0 01
380,000
4 , 54 5 M 3/ D = 1 M G D
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YEAR 1 1 0 ,0 0 0
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9 0 ,0 0 0
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Figure 2: Water Production Trend Plots Of Major Plants’ Over The Last Five (5) Years For The Island Of Trinidad
5
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REC. PRO DUCTIO N M3 /D
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)” 11,000 HILLSBOROUGH PRODUCTION GRAPH 1995 - 2001
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Figure 3: Water Production Trend Plots Of Major Plants’ Over The Last Five (5) Years For The Island Of Tobago.
6
High-Risk Groundwater Development Option for Small Island Developing States (SIDS)
islands indicated that we were using all available groundwater in proximity to high demand areas. New technologies to identify new sources of groundwater within the islands’ bedrock were identified as possible means of developing a reliable source of water for the public water system. Without the in-house expertise and the expectation that all the readily available groundwater was already developed, such a project was considered extremely high risk. High Risk Groundwater Development Approach New groundwater development on the islands has a great level of uncertainty and risk due to the unknown geological environments that require exploration. The degree of success of such a project is related to the quality of expertise applied to geological exploration and hydrogeological assessment of the groundwater potential of the islands. It is an axiom that the higher the risk in a project, the higher the costs to execute the project. Financial risk is high when those executing the project are lacking in expertise in the particular area being pursued. Risk reduction is therefore a major contributor to lower the cost of high-risk projects. One principle of risk management mandates that those with the greatest expertise in a specific area be charged with the responsibility of managing the risk associated with that area. By applying the best expertise to tackle a problem, risk would be reduced and cost reduced in direct proportion to the level of expertise engaged. Utilising the concepts of risk managementi, a groundwater exploration and development contractor was engaged through a competitive bidding process, to conduct a new hydrogeological assessment of the islands and to develop 15 MGD for the public water supply in Trinidad and 4 MGD for Tobago. The hydrogeological assessment of the islands was paid for on a lump-sum basis while the well staking and development of the required capacities was paid to the contractor on a “success basis”. The success basis proportion of the contract amounted to 90% of the total contract price. In this manner the major risk of the project associated with the geological uncertainty was borne by the contractor. His own competence in exploration will determine his successes in the more expensive well drilling phase of the project, but at his risk. The Authority would pay only for well’s throughput capacity after the wells were drilled, tested according to pre-agreed specifications and handed over. New Concepts and New Technologies Used Bedrock aquifers were conceptualized within the paradigm of “megawatersheds”. This new modelii describes the large scale fracturing and faulting architecture associated with the crystalline bedrock. These underlie several traditional surfical catchments from which infiltrated surface water provides substantial recharge to the megawatersheds. The exploration technologies to determine the existence and extent of these aquifers range from remotely-sensed data from satellite, airplanes, on-the-ground investigations and sub-surface investigations integrated on a Geographic Information System. These discrete data sets when
7
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
analyzed in an integrated manner were targeted to identify the complex network of fractures and faults (lineaments) pervasive on the island of Tobago and on the northern rain-rich portion of Trinidad. The following is a summary of the techniques employed: § § § § § § § § § §
Thematic Mapper Imagery to yield information on the morphology and structural features of the island’s surface. Satellite radar that penetrates vegetation is used to discern topographic features and surface roughness to differentiate rock types. Aerial Photographs yielded 3-D views of the island’s surface to infer the presence of lineaments and fractures. Digital Elevation Model data manipulation by changing vertical exaggeration, sun angle and azimuth yielded information on the linear features on the earth’s surface. Ground-thruthing of the implied fracture zones and faults by field surveys was used to confirm the presence of the structures. Geophysical surveys such as, resistivity, magnetic, seismic and gravimetric subsurface investigations, allowed the determination of geologic structure and the presence of fresh water. Delineation of the bedrock of the islands into smaller hydrological units based upon topography to provide the basic units of the hydrological analysis. Data from 12 years of weather satellites (Cropcast) analysis to determine precipitation and evapotranspiration on a daily basis. Hydrological Modeling of daily precipitation using watershed physical attributes to determine run-off on a daily basis. Hydrological Modeling to determine the amount of groundwater infiltration and recharge into the extensive fracture network of the postulated megawatersheds. GIS Integration of the diverse forms of data and interpreted information was used as the base for overlying diverse data sets allowing for superior definition of the fracture fabric system of the island.
The megawatershed aquifers that were delineated for the two (2) islands and their water potential are shown in Figures 4 and 5. The groundwater potential from these aquifers is 40 MGD for Tobago and MGD for Trinidad. The contractually required quantum of 4 MGD for the island of Tobago has already been handed over and greater than one-half has been put into supply already. At the time of preparation of this paper one-half of the contractually required 15 MGD for Trinidad has been identified. The other 7.5 MGD, targeted in the central portion of the island within sedimentary deposits has not yet been tested. Nonetheless, test-drilling sites have been identified and the current results of the drilling will be presented.
8
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
9
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
Reliability of Groundwater Production The island of Tobago can be cited as an example of successful groundwater development in previously unexploited geologic environments. Historically, groundwater development on the island was viewed as unfeasible due to the prevailing crystalline bedrock of the island. However, with the application of ‘state-of-the-art’ technology, proper expertise and risk sharing arrangements, subsequent exploration of the bedrock aquifers identified potentially prolific water producers. As a result, 40 MGD of previously undetected, renewable groundwater sources was identified for the island. The well development programme, initiated to exploit the potential water sources of the bedrock aquifers has yielded the following for the island: Ø Six (6) wells in the South West of Tobago were drilled producing a combined capacity of 3.5 MGD with five (7) associated monitoring wells. Ø Two (2) wells at Charlotteville were drilled producing a combined capacity of 0.1 MGD with one (1) associated monitoring well. Ø One (1) well in the North of Tobago was drilled with a capacity of 0.5 MGD with an associated monitoring well. Four (4) of these wells, producing a combined capacity of 1.9 MGD have been in production for 6 to 12 months to date. These wells have produced continually with a gradual decline in water levels to a maximum of thirty (30) feet. This, compared to the critical drawdown of ninety (90) feet indicates that the wells are producing from extensive megawatershed aquifers. Already, with the onset of the rainy season, following this year’s 1:50 drought, the water levels are stabilising and an increase in the levels is apparent. Even with only a proportion of the reliable well water-into-supply, there is a dramatic change in the class of supply throughout the island. This will be demonstrated pictorially using systems-modelling and GIS. With the additional water of the two (2) wells currently being put into supply, the improvement will be even more pronounced. The results of this modelling will be presented. The well development programme in crystalline bedrock aquifer systems has undoubtedly demonstrated the ability to discover and develop substantial quantities of high quality reliable groundwater. Conclusion The capital cost of the Tobago Groundwater Project was $US 5.5 Million whilst that of the Trinidad Groundwater project is projected to be $US 16 Million. For the Tobago project, the capital cost of $US 1.4 Million per MGD was realised; whilst, for Trinidad, the capital cost of $US 1.1 Million per MGD is projected. These costs include all incremental expenditure required to deliver water to the customer. In comparison, building an impounding reservoir in Tobago to deliver 5 MGD had an estimated capital cost of $US 12.0 Million per MGD and in Trinidad an impounding reservoir to produce 55 MGD had an estimated capital
10
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
expenditure of $US 3.5 Million per MGD. Operating expenditure to operate a wellfield has traditionally been one-half of that to operate an impounding reservoir. Apart from being an extremely attractive source of reliable water, with proper risk management, the Water Authority was able to minimise its own financial risk and thereby its cost of development, by engaging the contractor on a success basis. In other words, the risk has been transferred to the technology supplier who has the competencies to manage and minimise the risk. There are other attractive features of this approach over other competitive options. The project in Tobago was executed in nine (9) months, while in Trinidad it is anticipated to be completed in twelve (12) months. On the other hand, the gestation time to build an impounding reservoir was projected to be upwards of six (6) years and the desalination plant in Trinidad in reality is taking about three (3) years to complete. There has been much conjecture about the environmental impacts of the waste brine concentrate of the desalination plant, but by far, a worse environmental impact is the imminent destruction of an entire watershed in building an impounding reservoir. Groundwater development to date has virtually no adverse environmental impact, if abstractions are maintained within the safe yield of the aquifers. In Tobago, abstractions were well within the recharge estimates for each aquifer being exploited. From the experience on the islands of Tobago and Trinidad, we have concluded that groundwater development from bedrock geologic environments provide an extremely cost effective, zero environmental impact, short gestation time source of reliable water. Other SIDS within the Caribbean (and elsewhere) of similar geologies has access to a very attractive option to defend themselves against the vulnerability of their water supply to the vagaries of our seasonal weather patterns and to increase their water-into-supply. The Authority (WASA) of Trinidad and Tobago, in recognition of the continuous and increasing risks with surface sources, has adopted a strategy for groundwater development which will cause its groundwater production to increase from 23% to an estimated 50% of its total water production over the next five (5) years. Acknowledgments: The authors wish to thank Natalie Rowbottom-Huggins for her technical assistance on this paper.
i
“Risk Management in Groundwater Development – The Tobago Example” by Utam S. Maharaj presented at the Caribbean Water and Waste Association International Conference, Trinidad (2000)
ii
“Space-Age Integrated Exploration and Treatment of Renewable Regional Sources of Pristine Groundwater in Fractured Rock – Megawatersheds” by Robert Bisson in Desalination, 99 (1994), 257-273.
11
High-Risk Goundwater Development Option for Small Island Developing States (SIDS)”
Authors: Utam S. Maharaj, Tawari Tota-Maharaj Water and Sewerage Authority, Farm Road, St. Joseph, Trinidad Tel: (868) 663-7540/662-6333 Fax: (868) 662-3545/645-7933 E-Mail :
[email protected]/
[email protected]
12
Evaluation of the Improved Water Supply Intake for Surface Water Sources by Raphael Eudovique and Lester Arnold Water And Sewerage Company Inc., St. Lucia Abstract Increasing demand for water supply has made it imperative for water companies and authorities in the region and in particular, St. Lucia, to find new methods of improving the reliability of the service to their customers. Throughout the entire Caribbean region, approximately 80% of the regions water supply is from surface water sources and the remaining 20% is from ground water and salt/brackish water reserves. Customarily the majority of the surface water originates from rivers and water bodies tapped high up in the woodlands areas of the catchment. River intakes throughout the Caribbean region suffer from clogging due to siltation from the effects of poor land management practices in and around the catchments areas. The present day intake designs are not able to cope with the continued increase loading of debris and silt, which in many cases lead to the abandonment of the source(s). This paper demonstrates how the reliability of raw water abstraction can be improved and maintained by making minor but significant modifications to the intake structure. The results of a series of full-scale demonstrations of the intake improvement projects are summerised and the cost benefits emphasised. Keywords Increase demand, Improved Intake, Siltation, Debris, Cost benefits Introduction The island of St. Lucia depends solely on the availability of surface water in order to cater to the every day potable water needs of its inhabitants. The sole water company on the island, the Water and Sewerage Company Inc. (WASCO), operates 35 small to medium sized rural and urban water supply sources from within the 37 river catchments/basins in St. Lucia. Of these 35 sources which are tapped and utilized, there are 3 large treatment plants, 5 slow sand filters, 4 springs and the remaining 23 sources have only minimal sedimentation with all the treatment plants have terminal disinfections for all of the 35 sources. The smallest source produces as little as 10,000 gallons per day, whilst the average source produces approximately 250,000 gallons per day. The largest source produces on average approximately 6 MGD. The largest of the sources, which originates from the Roseau catchment area towards the centre interior of the island supplies water to the city and the northern part of the island, which accounts for approximately 65% of the population. All of the production figures quoted are based upon the rainy season months of June to December base flows and these figures can be reduced by as much as 75% of its total flow during the dry season months of January to May. The rural water sources, which comprise small and medium sources, are subjected to gross contamination in the rainy season. The rapid development of the banana industry in the late
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
1950’s and more recently, the growth of the tourism industry in the mid 1960’s have made increased demands on the water supply. Quantity and quality have thus become priority issues in the management of the natural resources. Construction activities, urban development, deforestation and poor agricultural practices have also contributed and are continuing to in one way or another to the pollution and deterioration of the water supply of the surface water in the rivers of St. Lucia. The soil lost in the eastern Caribbean including St. Lucia and the Latin American countries is approximately 1000 metric tons per square kilometre per year1 or approximately 4” of topsoil per year2. In the tropics, a single rainstorm can transport as much as over 70 metric tons of soil from one acre of land3. The average soil sediment discharge into the Caribbean Sea from the Magdalena river catchment basin in Colombia, South America is 220 million tons per annum with suspended solids level well over 1,000 mg/l 3. The current intake designs available in St. Lucia and also throughout the rest of the region are not able to cope with the relatively high levels of silt and debris loading. This results in interruptions to the water supply, which may take several days in some cases to be cleared. For many years, the then water authority before its transformation, the Water and Sewerage Authority (WASA) as it was formally known, had experimented with different types of modified intake designs. In 1998 the first of the improved intake design was commissioned at Thomazo, a small rural community in the village of Dennery on the eastern coast of the island. This source produces approximately 10,000 gallons per day and serves a community of about 500 people. Due to the success of this first installation, 12 other intakes have been modified using the improved intake design. The largest of the sources, the Millet intake on the Roseau River Catchment, is one of the 2 sources of the Roseau Dam Project has been outfitted with the improved intake design and was commissioned in 1999. This source produces over 6 million gallons of water per day and provides water to the city of Castries and the environs. The Existing Intake Designs As customary, an intake structure is required to withdraw water from a source, which may either be a river, spring or reservoir. Its primary function is to protect the pipelines and pumps from damage or clogging as a result of silt, floating or submerged debris. During and after a rainstorm the intakes often become clogged with different forms of debris. The present intake design which consist primarily of a well and associated pipe work cannot provide the much needed protection that is required to prevent the intakes from clogging and as a result quickly becomes clogged then with a subsequent interruption in water supply.
1
Milliman and Meade (1983), “Worldwide Delivery of River Sediment to the Oceans” Water and Environmental Management Project Report, 1995 3 Lloyd, Galvis and Eudovique (1991), “Evaluation of Multiple Barrier Principles in Drinking Water Treatment Systems for Surface Water Sources”, 20th Engineers Conference, Cayman Islands 2
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
FIG. 1 STANDARD WATER INTAKES UTILIZED IN ST. LUCIA The annually cost of de-silting the intakes in St. Lucia is approximately EC$500,000 with an average of over $15,000 per intake. Quite apart from the millions of dollars spent in desilting, the loss of water sales is even greater and an accurate figure cannot be sought but rather a speculative one. There is also the public health aspect, which is not often measured in dollars and cents but as a cost of providing health care to the country and not forgetting loss of productivity from the work force due to the ill – health of persons.
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
FIG. 2 A SILTED WATER INTAKE AFTER A RAINSTORM The other cost that must be considered which also contributes to the overall operating and maintenance cost of any one-water intake is the repair cost or replacement cost of these normal and standard water intakes. Depending on the severity of the rainstorm and the level of salutation, the damages to the intakes can be rather severe, with some of them warranting only minor repairs with other requiring total reconstruction as was the case with the Millet intake after the passage of Tropical Storm Debbie on 9 September 1994. This intake was severely damaged by the relatively huge boulders from within the watercourse and as a result had to be redesigned and rebuilt to order to cater to the live loads that it will be exposed to in terms of the sediment loading and dead load of the boulders. Repair cost to the intakes can vary from as little as $500 to as much as $30,000 whilst on the other hand reconstruction cost can start from as little of $25,000 to as much as $250,000 depending on the size of the intake.
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
Fig. 3 Silted and Damaged Water Intakes After a Rainstorm
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
FIG. 4 WATER INTAKE BEING DESILTED AFTER A RAINSTORM
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
INTAKE LOCATION Marquis Talvan Gravity Sources (6) Forestierre Desbarras Desrameaux Riviere Mitant Millet Vanard* Ravine Poission* Thamazo Aux Lyon Derniere Riviere Dennery Patience Micoud Dessuisseaux Belle Vue Vieux Fort Grace Saltibus (2) Choiseul Delcer Ruby Bouton Canaries Anse La Verdue Anse La Raye TOTAL AVERAGE
APPROX. VOLUME OF SILT (m3) 450 450 1300 220 220 200 200 500 1800 1800 200 220 220 450 220 450 400 400 1300 1300 900 220 1000 200 200 450 200 450
APPROX. COST OF DESILTING INTAKE ($) 12,600 12,600 36,400 6,160 6,160 5,600 5,600 14,000 50,000 50,000 5,600 6,160 6,160 12,600 6,160 12,600 11,200 11,200 36,400 36,400 25,200 6,160 28,000 5,600 5,600 12,600 5,600 12,600
15,920 568.57
444,960 15,891.43
Note: * no longer in operation
TABLE 1
SUMMARY OF THE CHARACTERISTICS AND THE AVERAGE COST OF DESILTING EACH INTAKE AFTER A RAINSTORM.
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
Concept Of The Improved Intake Designs Many types of intake filter designs have been tried in several countries all over the world with varying levels of success. Traditionally, intake filters are installed directly onto the intake pipe placed inside the chamber or in a deviation wall. As indicated before, these do not work and time and money is spent to clean and restore the water supply after a rainstorm. The water company produces a total of approximately 3,741 million gallons of water per year. On average 15% of the total production from these intakes are loss due to clogging in the rainy season and another 10% in the dry season due to falling leaves. The improved intake design has enabled the St. Lucia water company to utilize this 25% or 935 million gallons per year of the production from the intakes both in the wet and dry seasons. The improved intake design has enabled to be continuously used without having to de-silt or minimize the clearing of the falling leaves. The idea of re-designing, improving on the original design and also the building of new intakes has proved to be too expensive. The alternative was to incorporate the new idea into the exciting structure.
Fig. 5 The New Intake Design
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
Design And Application Of The Improved Intake Filter Intakes are normally constructed with an intake chamber where the water enters through 2” holes on the sidewall. Access into the chamber is through a 3’- 0” square manhole at the top, covered with a concrete slab. Inside this chamber is the intake pipe with a course mesh screen at the end. After a rainstorm and even during normal weather conditions the holes are easily blocked with silt and debris or with fallen leaves in the dry season. The improved intake allows the water to enter through the manhole at the top. The water is channeled to the manhole through a series of course, medium and fine screens respectively. The screens are placed at a slope of between 5 – 10o to allow for a self- cleaning effect. The channel is designed to generate sufficient velocity to carry away floating and suspended material including sand but at the same time allowing water to filter through the screens. The most critical aspect of the design is to get the right velocity and slope for maximum efficiency. The ideal velocity for the slope mentioned is between 1ft – 5ft per second. In order to achieve the desired velocity, the shape and size of the channel must be carefully selected. To achieve a velocity of 5 ft/sec., the channel should be narrow , whereas for a velocity of 1 ft/sec., the channel should be wide. The design of the channel chosen will depend on the flow in the river. If the flow in the river is high, then a low velocity channel may be used, whereas if the flow in the river is low then a high velocity channel should be used. SLOPE (Deg) 5 6 7 8 9 10
VELOCITY (ft/sec) 5.15 4.32 3.49 2.66 1.83 1.0
TABLE 2 ILLUSTRATES THE SLOPE AND THE CORRESPONDING VELOCITY In Table 2 above, it is noticed that with a slope of 50 the velocity is 5.15 ft/sec. where as with a slope of 100 the velocity is reduced to 1 ft/sec. The approximate cost of converting an existing intake to the improved design ranges from EC$4000.00 to $10,000.00 depending on the size of the intake and the extent of work to be done. Having studied the modified intakes for a few years it has been observed that the advantages far outweigh the disadvantages and that the improved intake designs have better cost benefits. Some of the advantages and disadvantages are outlined below and are as follows:
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
Advantages It provides for a self-cleaning system. As the water flows over the screen fitted in the manhole chamber, it washes away all the suspended material such as leaves and sand in the water. The ability for this system to self- cleanse itself saves on cost of maintenance at the intake and reduces the need for visits to the intake by the caretaker. Provides a more effective and efficient screening system. The screens over the chamber comprises of three different mesh sizes. The largest size being 1cm x 1cm, the other 0.5cm x 0.5cm and the smallest is 1mm square. With these screens in place it minimizes the entry of suspended material into the chamber. Requires no de – silting of the intake. The improved intake requires no de-silting. The silt entering the chamber is very fine and in suspension and will not affect the continuity or flow of the water for production. They will require fewer visits by the work crew to the intake thereby allowing more time to attend to other operational matters. Provide continuity in the water supply. It has been established that even in the rainy season, when the river swells and floods over its banks that the improved intake operates best. Floating debris is carried away, thereby maintaining a full chamber. Reduces on down time. The possibility of intake clogging is significantly reduced thereby reducing the down time and maintaining a more even production level. Disadvantages Unsightly appearance of the intake. The design of the original intake enhances the build-up of silt and debris up stream of the intake. This build- up of silt and debris cause the intake to be unsightly. Partial clogging of screens. Depending on the severity of the dry season, water level in the river maybe so low thereby reducing the self- cleaning process on the screen and as a result increases maintenance.
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Evaluation of the Improved Water Supply Intake for Surface Water Sources
FIG.6 MODIFIED INTAKE DURING THE DRY SEASON LOCATION OF INTAKE
WORK DONE
Marquis Talvan Millet Thomazo Aux Lyon Derniere Riviere Dennery Micoud Desruisseaux Delcer Canaries Anse La Raye
Removing dry leaves and other forms of debris on screens
575
TOTAL AVERAGE TABLE 3
APPROX. COST OF CLEARING SCREENS ($) 1,200 1,200 1,200 300 300 300 300 300 900 300 300 300
ILLUSTRATES THE AVERAGE COST OF MAINTAINING AND CLEANING THE IMPROVED INTAKE SCREEN
23
Evaluation of the Improved Water Supply Intake for Surface Water Sources
In designing and constructing the modified intakes care must be taken in locating the inlet chamber at the right height in order to maximize the amount of water being extracted and to also ensure continued operation during the drier months of the year. Therefore in comparison it is noted that the average cost of maintaining and cleaning the improved intake is approximately $575 as against $15,891.43 for the original style of intakes. Conclusion The evaluation of the improved intake design has demonstrated that the advantages far outweigh the disadvantages of the project. As with all research projects there are always advantages and disadvantages. However, the disadvantages are measured in terms of the level of risk involved, which in this case is relatively low. On the other hand, the overall cost of the retrofitting of existing intakes plus the average cost of maintenance is approximately $8,575 and is far less than the average cost of maintaining the standard intake prior to the redesign of $15,891.43. The improved intake design provides for self-cleansing, a more effective and efficient screening process, requires little or no desilting of the intake, reduced down time of intakes and finally a continuity in the water supply to communities thereby making more water available to the consumers. References Milliman J.D. and Meade R.H. (1983) “Worldwide Delivery of River Sediment to the Oceans”, Journal of Geography, Vol.91, pp. 1-21 Water and Environmental Management Project Report Lloyd B.,Galvis G., Eudovique R. (1991) “Evaluation of Multiple Barrier principles in Drinking Water Treatment Systems for Surface Water Sources”, 20th Engineers Conference, Cayman Islands Eudovique R. (1992) “Integrating Surface Water Treatment Processes for Rural Communities”, MPhil. Thesis, University of Surrey, UK Galvis G. (1992) “The Development and Evaluation of Multistage Filtration Systems for Community Water Supply in Colombia”, PhD Thesis, University of Surrey, UK Authors: Raphael Eudovique and Lester Arnold Water and Sewerage Company Inc. P.O. Box 1481 Castries St. Lucia
24
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement by E. Lawrence Adams, JR., P.E., DEE, Camp Dresser & McKee Inc. and Grenville S. Marsh, Consultant to Camp Dresser & Mckee INC. Introduction New Providence Island is the most highly populated of the islands forming the Commonwealth of the Bahamas. The capital and chief commercial center is Nassau which, with its environs, occupies the whole of New Providence. Most of the water distribution network on New Providence is owned and maintained by the Water and Sewerage Corporation (WSC). The distribution network includes over 440 miles of mains and a large part of the network has been in service for several decades with sections in certain parts of Nassau installed over 50 years ago. The principal sources of water to the existing system are as follows: 1. 4.0 mgd which is transferred by tanker from wellfields on Andros to Arawak Cay on New Providence. 2. 2.0 mgd produced by the WSC wellfields at the west end of New Providence which is blended with 2.0 mgd from the Waterfields seawater reverse osmosis (SWRO) facility adjacent to Windsor. This total is ultimately pumped from Windsor pumping station. 3. 0.2 mgd produced by the Perpalls wellfield and which is delivered to Prospect. 4. 0.2 mgd produced by the Blue Hill wellfield and which is delivered to Blue Hill Low Level. There are five major pumping stations on New Providence located at Windsor, Prospect, Arawak Cay, Blue Hill and Winton. WSC had been experiencing severe leakage problems in the system for a number of years with 700 leaks repaired on the mains and 6,300 leaks repaired on services in one year recently. Additionally, much of the older cast iron pipe had been experiencing corrosion problems, causing water quality complaints from consumers. Another source of customer complaint had been the poor residual pressures in the system. WSC entered into an agreement with Camp Dresser & McKee Inc. (CDM) on March 21, 1996 to provide consulting engineering services for studies, design and construction of various components for Water Supply Improvements in New Providence and Expansion in the Family Islands. As part of this work, CDM prepared a feasibility study, designed the recommended improvements and provided services during construction of pipeline installation and refurbishment in New Providence. The work performed was funded by a loan from the European Investment Bank (EIB).
25
Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
A Pre-Feasibility Report was used as the basis for the Terms of Reference submitted to CDM. The report identified specific mains on New Providence that were recommended for rehabilitation. The purpose of the Feasibility Study was to review the recommendations for mains rehabilitation made in the Pre-Feasibility Report and to also assess if any additional mains should be included in the Study. Objectives and Project Scope The Feasibility Study evaluated cost-effective solutions for: 1. Reducing unaccounted-for water 2. Achieving better system pressures 3. Improving water quality The mains identified for rehabilitation were presented in the Feasibility Study in four groups. 1. Mains requiring refurbishment (slip lining or cleaning and lining). 2. Mains requiring replacement or upgrading (either replace in some locations or upgrade by replacing with larger diameter pipes). 3. New mains to reinforce the system network. 4. New mains. The total length of mains requiring refurbishment was approximately 13 miles. The total length of mains requiring replacement was approximately 27 miles. The rehabilitation work represented about 10 percent of the total distribution network on New Providence. The mains requiring rehabilitation are shown on Figure 1. Following the submittal of the draft study in June 1996, further discussions were held with the WSC and several mains were either curtailed in scope or amended. Unaccounted-For Water The level of unaccounted-for water (UFW), the difference between water production and billed water consumption, was approximately 49 percent on New Providence and this was a major concern to the WSC. The added O&M costs for UFW are reflected in electrical costs, manpower, equipment and production costs of the Andros shipping operation. Model Review CDM met with the WSC personnel in mid 1996 to review the KYPIPE New Providence water distribution system model. The goal of the review was to ascertain the status of the existing model and to recommend additional tasks. The additional tasks were required to upgrade the model for running scenarios to determine the effect of water main improvements on the pressures at various locations within the water system. Table 1 shows the results of these model runs. 26
Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
27
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
Table 1
New Providence – Mains Refurbishment /Replacement WATER SYSTEM PRESSURES FOR AVERAGE OPERATING CONDITIONS
Area Westward Villas Cable Beach Oakes Field South Beach Estates Seven Hills Elizabeth Estates East Bay Street Village Road East Street North Blue Hills North Coconut Grove Johnson Road Eastern Road Step Street
Approximate Location of Pressure Reading West Bay Street West Bay Street/Prospect Road Thompson Blvd/Poinciana Dr. East Street/Bamboo Blvd. Blue Hill Road/Cowpen Road Yamacraw Rd/Commonwealth Blvd. Eastern Road/Shirley Street Village Road/Shirley Street Market Street/Lewis Street Blue Hill Road/Wulff Road Coconut Grove Avenue/5th Street Johnson Road/Kelly Lane Eastern Road/Johnson Road Step Street/Rahming Street
28
Existing (psi)
With Improvements (psi)
35-45 15-25 20-25 20-25 15-20 10-15 20-25 15-20 15-25 15-20 15-25 20-25 35-40 15-20
50-55 35-40 45-50 45-50 35-40 20-25 35-40 20-25 30-35 20-25 35-40 45-50 60-65 25-30
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
Field Investigations As part of this study, a field review of the mains routings was undertaken to determine the general physical conditions and the constraints relating to refurbishing or replacing the mains. Coupons were taken on the key mains to be refurbished. Coupon is the term for a short section of any pipe that is cut out and removed for inspection and analysis. The coupon is typically selected at a location on the main that could reasonably be expected to represent the average condition of the pipe at that location. The taking of a coupon also allows a physical review of trench and groundwater conditions, and an inspection of the undisturbed pipe, as well as an opportunity to observe any discoloration in the water in the main. The main is typically returned to service by installation of a repair sleeve. Many of the coupons taken showed that the interior walls of the pipe had extensive tuberculation, especially in the smaller diameter pipes. This, in turn, resulted in decreased flow capacity and led to discoloration of the water. No coupons were taken on any of the replacement or new mains included in the scope of work. The coupons were submitted to a recognized testing laboratory for review and for a determination that each of the mains was in a satisfactory condition to accept rehabilitation. The laboratory results showed that the mains submitted for analysis were suitable for refurbishment. Of particular concern to the WSC was the 20-inch ductile iron pipe (DIP) along John F. Kennedy Drive (JFK main) which is the key transmission main transferring water from Windsor into distribution. This main experienced major leaks over a 20,000-foot section, with one localized section parallel with Lake Cunningham experiencing 14 leaks in one fourmonth period. There were also periods when the pump operating pressure at Windsor was reduced from 90 psi to 60 psi in an effort to reduce the number of leaks. Field investigations on this main indicated that the pipe was pitting and corroding from the exterior. Methods of Mains Refurbishment JFK Main A study was performed on the JFK main to analyze the causes of the numerous leakage problems and to present a course of action to remedy the problem. An approximate two-mile section of the JFK main parallel to Lake Cunningham was where the majority of the leakage repairs had taken place. Additionally, the elevation of the main in this section was similar to the level of the water in the lake. At the locations where the JFK main was exposed for inspection purposes, there were signs of external corrosion to the pipe wall. The cause of the degradation was attributed to the pipe being within the tidal influence of the brackish water in the lake. 29
Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
As the JFK main is a large diameter transmission main with few branches and no service connections, the option of sliplining appeared appropriate and was evaluated. Sliplining with HDPE pipe was reviewed, as this type of pipe would give the structural integrity required should the wall of the existing ductile iron pipe deteriorate further in the future. However, the thickness of the HDPE liner required was found to drastically reduce the diameter of the existing main and hence the flow capacity of the main, and also increase power costs. Further options looked at for the JFK main refurbishment included the installation of HDPE pipe as a replacement pipe laid along the bottom of the lake in the section where the main runs parallel with Lake Cunningham. This was discarded as impractical due to possible damage by boats, the difficulty of pipe installation and maintenance and the fact that any leakage would go undetected. The most economical solution for the JFK main rehabilitation was to replace the ductile iron pipe with a parallel PVC pipe main of the same diameter in the areas where major leakage problems had previously been identified. This allowed this key transmission main to remain in service with the only interruptions during installation occurring during tie-ins between the PVC and DIP pipe at various locations. The PVC main was typically installed outside the existing paved roadway. Remainder of the Mains Requiring Refurbishment Options considered for the remainder of the mains refurbishment included cleaning only, cleaning and cement lining, epoxy lining and pipe displacement. Table 2 tabulated the advantages and disadvantages of each of these methods. Following evaluation, the cement lining option which is recognized as an established and satisfactory method of pipe rehabilitation that will eliminate leaks, and offer a along service life was the rehabilitation method selected as the most cost-effective for the refurbishment of the mains on New Providence. Pipe Material Evaluation for Mains Replacement A key factor for this project in consideration of a pipe material was the pipe cost, as lower overall costs would enable more mains to be replaced. Ease of pipe handling and field assembly were also important factors due to the constraints of the site conditions in certain areas of the project. For these reasons PVC was the preferred pipe material as it would allow easier cutting to suit field conditions in congested work areas. Additionally, corrosion does not present a problem if PVC is used.
30
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement NEW PROVIDENCE - MAINS REFURBISHMENT/REPLACEMENT TABLE 2 METHODS OF REFURBISHMENT
Clean Only Advantages
Disadvantages
Typical Pipe Size
Clean and Cement Lining
Epoxy Lining
Pipe Displacement (Bursting)
Provides a quick fix with low cost. Line
Established and satisfactory method.
Liner thickness approximately 1.0 mm.
Allows pipe size to be increased one
soon back in service. Should be used
Use rapidly expanding. Removes
Liner does not bridge service main "gap".
size. Uses existing pipe location for new
only as prelude to cement lining.
possibility of tubercalation returning.
Quicker return to service than cleaning
main. Minimum disruption to traffic.
Eliminates leaks.
and lining (8-10 hrs). Eliminate leaks.
Eliminates leaks. New pipe to be installed at same depth
Limited life. "C" factor returns to pre-
Line has to be clear of external corrosion.
Skilled operators required. No structural
cleaned state very quickly. Produces
Keeps line out of service for minimum of
improvement in main. Line to be
as existing. Can cause "moling" effect
red water.
24 hours. Length limited by bends
completely clean before application.
and damage to existing parallel utilities.
22 1/2" and over.
TV before lining.
Service connections must be excavated.
6-inch and above.
Up to 12". In UK up to 6".
All sizes.
In UK 8-inch and above. Typical Length of Section 1,000 feet
Most appropriate for sizes to 8 inches with 3 feet minimum cover.
500 - 600 feet
500 - 600 feet
1,000 feet
50 years or related to condition of host
15 to 20 years
Dependent on material of replacement
for Rehabilitation Approximate Length
3 to 5 years
of Service Following
pipe.
pipe.
Rehabilitation Approximate Cost per
$2 to $5 including TV inspection
$25 to $50 for 6" - 12".
$30 to $50 for 6" - 12".
Linear Feet Notes
An option that is not recommended as
Double thickness of cement lining
Not widely used for potable water mains.
a method of rehabilitation (included for
frequently specified. Labor intensive
Little heard of use in USA.
reference only).
about 30% to 50% cost of replacement.
31
$20 for 6".
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
Although, typically, the internal diameter of PVC pipe is smaller than that of ductile iron pipe of the same size, the increased flow characteristics compensate for the decreased flow area. PVC pipe with ductile iron fittings was the recommended material for pipe replacement, network reinforcement, and new mains for this project. Pipe Cost Determination The estimated costs used in the Feasibility Study for the mains refurbishment/replacement and new mains were based on a review of available existing data. These included: §
New pipe and fittings prices obtained in June 1996 from recognized manufacturers of ductile iron pipe, polyvinyl chloride pipe and high-density polyethylene pipe with prices of materials reflecting delivery to Nassau.
§
Review of the bids received for the Trunk Water Mains Refurbishment project on New Providence in January 1990 (cleaning and lining 18" and 21" steel mains, sliplining 16" steel mains) and bids received for various water mains cleaning and lining and pipe installation projects in the Bahamas and the USA
The estimated costs of each of the mains to be refurbished or replaced and additional mains were calculated on the basis of a fixed cost per foot of pipe. The cost per foot included the cost of material and installation and included all items of work normally associated with pipeline work, including fittings, valves, restoration and the like with an allowance added for inflation. Water Mains Rehabilitation The amount of electrical power savings due to main rehabilitation was estimated. The HazenWilliams equation was used to compute the head losses for each section of pipe, both for existing conditions and for estimated conditions after rehabilitation. The differences in head losses between the two were multiplied by the cost of electricity and the annual cost savings in electrical energy was discounted for 20 years at a rate of 6.8 percent to estimate total present worth savings in electrical power resulting from the rehabilitation. For each pipeline, from the estimated cost of rehabilitation, the total present worth cost of electrical energy savings was deducted. From this difference is then deducted the estimated amount of total present worth savings of leakage correction. Based on costs developed by WSC for leak repair and including the value of lost water at the estimated variable cost of
32
Commonwealth of the Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
$8.00 per thousand gallons, the average cost of leakage was estimated as $0.15 per linear foot per year. Again, using WSC estimates based on previous experience, the average cost of leakage for the JFK main was estimated as $0.60 per linear foot. The annual cost of leak repair was discounted for 20 years at 6.8 percent to derive the total present worth savings. The net cost of rehabilitation was used to rank quantitatively pipelines for rehabilitation. Due to funding constraints and as it was undefined at the time of the Feasibility Study what part of the total budget would be available for the mains rehabilitation, a ranking procedure was developed to determine the order of importance for individual main rehabilitation. Qualitative factors used to rank the pipelines for rehabilitation were: (1) importance of the main to the system; (2) leak history; (3) pressure increases; and, (4) technical requirements of main installation. Points were given based on a range from key transmission mains, which received 10 points, down to a subdivision service main, which was scored as 1 point. Percentage increases in pressure varied from 10 points for a 100 percent or greater increase, down to 1 point for less than a five-percent increase. Pressure increases were determined from the model analysis. Concerning leak history, points were allocated based on the leakage history of the main with a high leakage rate scoring 10 points, to little or no leakage history receiving 1 point. Regarding the technical requirements of mains installation, a value was assigned to each main for the difficulty of construction with respect to type and size of pipe, the location in the system, and estimated cost of the work; the greater the technical requirements, the higher the ranking. A weighting value was assigned to each of the qualitative weighting factors: 50 percent to importance to the system; 20 percent to leak history; 20 percent to pressure increases; and, 10 percent to technical requirements of the work. The raw score for each parameter was then multiplied by these weighting factors to derive the weighted qualitative factors. Summing these factors yielded a total score for qualitative factors. The pipelines were then sorted in descending order of total for the weighted qualitative factors, and these are shown in Table 3. Conclusions The pipe ranking system developed for this project determined the importance of each main to be rehabilitated on the basis of quantitative and qualitative factors. The ranking was used to implement a cost-effective approach to the refurbishment/replacement program by ensuring that the most critical mains received the highest priority for rehabilitation. In the period since the mains rehabilitation work there have been noticeable improvements in water pressure and water quality in the system.
33
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement NEW PROVIDENCE - MAINS REFURBISHMENT/REPLACEMENT TABLE 3 WATER AND SEWERAGE CORPORATION EVALUATION OF PIPELINE REHABILITATION: FINAL RANKING - SORTED QUALITATIVELY
Weighted Qualitative Factors Technical Pipeline
Importance
Leak
Pressure Req'mts
Number Routing
to System
History Increase
of work
Net Est'd
Estimated
Estimated
Total
Cost of
Cost of
Cost of
(1)
Rehab.(2)
Rehab.
Rehab.
A1
JFK Drive
5.0
2.0
0.2
1.0
8.2
$2,250,400
$2,500,000
$2,500,000
A8 A4
West Bay Street (Coral Dr.) Blue Hill PS/Ft Fincastle
4.0 5.0
0.8 1.2
2.0 0.8
0.8 0.5
7.6 7.5
$4,125 ($83,500)
$365,625 $138,000
$2,865,625 $3,003,625
C2
Soldier Rd/Blue Hill Rd.
4.0
0.8
2.0
0.7
7.5
$1,271,600
$1,164,000
$4,167,625
B2
Bernard Road
3.5
1.6
1.6
0.5
7.2
($586,900)
$600,000
$4,767,625
B10
West Bay Street (Blake Rd.)
4.5
1.2
0.6
0.7
7.0
$587,600
$760,000
$5,527,625
A2a
Fincastle Ridge (East)
4.0
1.2
1.2
0.5
6.9
($39,100)
$456,000
$5,983,625
B3 D1
Thompson Blvd. East Bay street
3.5 4.0
0.8 0.8
2.0 1.2
0.5 0.8
6.8 6.8
($428,200) $1,275
$438,000 $108,875
$6,421,625 $6,530,500
B5
Market Street (North)
3.0
1.2
2.0
0.5
6.7
($514,300)
$219,000
$6,749,500
B12
Eneas Avenue
3.0
1.2
2.0
0.4
6.6
($175,000)
$145,000
$6,894,500
B13
Bethel Avenue
3.0
1.2
2.0
0.4
6.6
($63,400)
$212,500
$7,107,000
C1a
Dowdeswell St.
3.0
1.6
1.2
0.8
6.6
$2,000
$156,000
$7,263,000
A6 B6
East Street (South) East Street (North)
3.5 4.0
1.2 1.2
1.2 0.8
0.7 0.5
6.6 6.5
$6,200 ($555,500)
$507,000 $236,400
$7,770,000 $8,006,400
A3
Blue Hill Road (North)
4.0
1.2
0.8
0.5
6.5
$175,200
$325,000
$8,331,400
D4
Shirley Street (West)
4.0
0.4
1.2
0.8
6.4
($127,750)
$217,750
$8,549,150
B1
Eastern Road
3.0
1.2
1.2
0.8
6.2
($1,439,000)
$555,000
$9,104,150
A5
Blue Hill Road (South)
2.5
1.2
2.0
0.4
6.1
($474,800)
$75,000
$9,179,150
D10 D2
Market Street (South) Johnson Road
4.0 4.0
0.8 0.4
0.8 1.2
0.5 0.5
6.1 6.1
($262,600) ($79,900)
$141,000 $290,000
$9,320,150 $9,610,150
A2b
Fincastle Ridge (West)
3.5
1.2
0.8
0.5
6.0
$36,350
$81,250
$9,691,400
B4
Kemp Road
3.0
1.2
1.2
0.5
5.9
($309,600)
$132,000
$9,823,400
B7
Shirley Street (East)
3.0
1.2
1.2
0.5
5.9
($190,700)
$169,200
$9,992,600
D6
Stapledon Gardens
2.5
1.2
2.0
0.2
5.9
($44,000)
$200,000
$10,192,600
B8 B14
Augusta Street Step Street
2.5 2.5
0.8 1.2
2.0 1.6
0.5 0.4
5.8 5.7
($132,500) ($247,100)
$110,000 $205,000
$10,302,600 $10,507,600
B11
Malcolm Road
2.5
0.8
1.2
0.4
4.9
($185,200)
$189,000
$10,696,600
A7
S. Beach Rd./blue Hill Rd.
2.0
1.2
1.2
0.4
4.8
($16,400)
$171,600
$10,868,200
B9
Cordeax Avenue
2.5
0.8
0.8
0.5
4.6
($129,500)
$107,500
$10,975,700
B17c
Garden Hills Subdivision
1.5
2.0
0.8
0.3
4.6
$45,700
$57,300
$11,033,000
B17b B17a
Garden Hills Subdivision Garden Hills Subdivision
1.5 1.5
2 2
0.8 0.8
0.3 0.3
4.6 4.6
$319,000 $508,100
$356,000 $564,000
$11,389,000 $11,953,000
B16
West Avenue
2
0.8
1.2
0.5
4.5
($101,100)
$83,500
$12,036,500
D7
Highland Park
1.5
0.8
2
0.2
4.5
($25,400)
$112,500
$12,149,000
D8
NW Highland Park
1.5
0.8
2
0.2
4.5
($19,700)
$100,000
$12,249,000
B15
7th Terrace
D11 D5
Armstrong Street Hillview Drive East
2
0.8
1.2
0.5
4.5
($17,800)
$15,000
$12,264,000
2 1.5
0.8 0.8
1.2 1.6
0.5 0.5
4.5 4.4
($15,200) ($50,000)
$33,000 $190,800
$12,297,000 $12,487,800
C3
Cow Pen Road
1.5
0.4
2
D9
Rahming Street
1.5
0.8
1.6
0.4
4.3
$193,600
$171,000
$12,658,800
0.2
4.1
$16,700
$60,000
$12,718,800
D3
Balfour Avenue
2.0
0.4
0.8
0.2
C1b
Mackey St. to P.I.
1.0
0.2
1.2
1.0
3.4
$39,700
$140,000
$12,858,800
3.4
$201,650
$281,250
$13,140,050
1. Pipelines ranked in descending order by Total of Weighted Qualitative Factors. 2. In cases where Weighted Qualitative Factors result in a tied Total, the pipelines with tied scores are ranked in ascending order of Net Estimated Cost of Rehabilitation.
34
Commonwealth of The Bahamas Water and Sewerage Corporation New Providence Mains Refurbishment/Replacement
Authors: E. Lawrence Adams, JR., P.E., DEE Camp Dresser & McKee Inc. 6365 N.W. 6th Way, Suite 320 Fort Lauderdale, FL 33309 E-mail:
[email protected] and Grenville S. Marsh Consultant To Camp Dresser & McKee Inc.
35
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands by Brian Jones1, Hendrik-Jan van Genderen2 Tom van Zanten2 1
Department of Earth and Atmospheric Sciences, University of Alberta 2 Water Authority Cayman, Cayman Islands
Abstract In 1994 the Water Authority-Cayman determined that the drinking water production capacity for the piped water supply of Grand Cayman needed to be expanded from 5,000 m3/day to 6,500 m3/day in 1998 and to 8,000 m3/day in 1999 in order to meet projected demand. Thus, a new reverse osmosis plant was planned for Lower Valley, approximately 15 km east of the plant in George Town. In the Cayman Islands the saline water needed for reverse osmosis plants is typically abstracted from deep wells whereas the dense brines produced by this process are disposed into zones located deeper than the abstraction zones. The challenge of this project was to design and install a well-field that would not result in degradation of the shallow freshwater lens. The geology of the Cayman Islands does not provide confined or semi-confined aquifer zones, which would preclude migration of the shallow fresh groundwater to the deeper feed wells or migration of brine to shallower depths. A preliminary groundwater model of the aquifer was created to simulate the effects of different well-field designs under varying horizontal and vertical permeabilities in the aquifer. A pilot well was drilled at the site, rock samples from this well provided site specific detailed geological information. The freshwater lens is located within the Ironshore Formation and the underlying transition zone is located within the Pedro Castle Formation. The low porosity cap rock of the Cayman Formation effectively isolates the freshwater lens from water circulation in the deeper part of the succession. The well-field abstracts saline water from an open zone below the cap rock of the Cayman Formation at a depth of 45–65 m with brine disposal at a depth of 62–86 m, the bottom of the brine disposal zone is highly cavernous. The plant became operational in 1998, and production capacity was doubled in 1999. To date the Lower Valley reverse osmosis plant has been operating successfully without adverse effects on the Lower Valley freshwater lens. This is evidenced by water quality data obtained from a network of monitoring wells designed to monitor the effects of the plant on the freshwater lens. Key Words: Grand Cayman, well-field design, freshwater lens, Ironshore Formation, Pedro Castle Formation, Cayman Formation, Cayman Brac Formation, groundwater monitoring, reverse osmosis.
36
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Introduction The provision of high quality drinking water is a challenge for any island that has limited fresh ground water resources, lacks a surface water supply and is faced with an ever increasing population of permanent residents and tourists. Under such a scenario, the traditional water supplies obtained from small, localized freshwater lenses and individual rainfall catchment will eventually prove inadequate. Such has been the case on Grand Cayman, Cayman Islands. The Cayman Islands, a British Crown Colony, consists of three flat limestone islands located in the northwest Caribbean, latitude 19o20’N and longitude 81o20’W, 724 km south of Florida (Fig 1A, insert). The Water Authority of the Cayman Islands, established by law in 1982, commenced the installation of the George Town Piped Water Supply System in 1987 to meet the growing demand for a reliable water supply in Grand Cayman. Potable water for this system is obtained from desalination of saline groundwater, as fresh groundwater resources in George Town are insufficient for large scale commercial exploitation. Initially the water supply system was designed to supply 1,000 customers in the George Town district; currently it has been expanded to supply 8,000 customers in the districts of George Town, Bodden Town and East End (Fig 1). It is the Authority’s intention to expand the system to the North Side district. The demand for piped water has increased significantly from an annual average of 800 m3/day in 1988 to 6,000 m3/day in 2000 as a result of the rapid increase of the population in Grand Cayman from 24,000 in 1989 to 37,500 (Cayman Islands Census 1999) and the expansion of the distribution system from 40 km of mains in 1988 to 300 km by the end of 2000 (Fig 2).
37
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Figure 1. Geology of Grand Cayman, location of major fresh water lenses (A) and cross section of Lower Valley freshwater lens (B). Modified from Ng (1990).
38
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
7,000 6,000 5,000 4,000 3,000 2,000 1,000 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Figure 2. Water Authority Cayman sales of piped water, average daily demand by year, 1988 to 2000 (m3/day) In 1994 the Water Authority determined that the water production capacity needed to be expanded to meet increasing demand from 5,000 m3/day to 6,500 m3/day in 1998 and to 8,000 m3/day in 1999 (Water Authority 1994) to satisfy dry season demands, which can be 20 to 25 % higher than average demand. Such an increase could only be met by construction of a new reverse osmosis plant. As the original plant was located in George Town, it was determined that the new plant should be located further east to continue operational reliability of the water supply system. The most suitable location from an operational and practical point of view was Lower Valley, which is located about 15 km east of George Town (Fig. 1). This inland site was selected because the Water Authority already owned the land and zoning laws precluded an alternative suitable location within the distribution area. In the Cayman Islands the saline water needed for reverse osmosis plants is typically abstracted from deep wells whereas the dense brines produced by this process are disposed into zones located deeper than the abstraction zones. Locating the reverse osmosis plant at Lower Valley meant that it had to be built over one of the three freshwater lenses on Grand Cayman (Fig 1) (Ng 1990; Ng et al. 1992; Ng and Jones 1995). This was a major challenge as the limestone-dolostone geology of the Cayman Islands does not provide confined or semi confined aquifer zones, which would preclude the migration of the shallow fresh groundwater to the deeper abstraction wells or the migration of brine to shallower depths. Consequently, the well-field for the reverse osmosis plant had to be designed and installed so that it had no adverse effects on the quality of the freshwater lens, which was to be maintained for local usage. Faced with this prime mandate, the challenges were to (1) identify a highly permeable abstraction zone that would allow long-term abstraction of large volumes of saline water, without affecting the shallower freshwater lens, (2) identify a highly permeable disposal zone, located deeper than the abstraction zone, where the concentrated
39
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
brines produced by the desalinization process could be disposed, and (3) ensure that the brines introduced into the disposal zone would not migrate upwards into the abstraction zone. It was immediately recognized that the solution to these challenges lay in (1) developing a preliminary groundwater model to predict the effects of abstraction of saline groundwater and disposal of brine on the shallow fresh water lens, (2) obtaining detailed information on the subsurface geology of the area, and (3) careful installation of the wells. Furthermore, in order to verify that the lens would not be impacted by the well-field operation the condition of the lens had to be closely monitored.
Preliminary Groundwater Model The dolostone aquifer of the Lower Valley area is characterized by secondary porosity in the form of open joints, fissures, solution channels and caverns. Due to lack of availability of specific data on permeability of the deeper aquifers and the high degree of anisotropy and heterogeneity of the aquifers in the Cayman Islands, groundwater modeling was limited to comparison of several scenarios for abstraction: variations in casing length, variations in permeability of different layers of the aquifer and variations in vertical and horizontal permeabilities. Data for the model were based on the literature and limited field data from previous testing on shallow aquifers in the Cayman Islands. Due to these limitations the model could not make quantitative predictions, however it was possible to predict the effects on the aquifer qualitatively. A finite-difference model was created using the Excel spreadsheet program; the model is a steady-state three dimensional multi-layer ground water model with optional different horizontal and vertical permeabilities. The model consists of 18 layers, with 144 nodes per layer; each node represents an area 10 m thick by 20 m long and 20 m wide. In preparing the model the following assumptions were made: (1) Darcy’s Law is applicable (i.e. groundwater flow is laminar), (2) an impermeable layer exists at 170 m below the groundwater table, and (3) a constant head condition exists at 220 m distance from the well. Brine disposal was not included in the model, as this was not identified as a direct threat to the shallow fresh water lens. It is practice in the Cayman Islands to construct the open zone of brine disposal wells below the open zone of abstraction wells. Vertical anisotropy, high permeability of the aquifer and the higher density of the brine will promote lateral and vertical downward flow over vertical upward flow (Water Authority 1995). The results of the model calculations for the abstraction wells were that: ·
The contribution from the shallower layers (fresh to 8 m below water table and brackish water from 8 to 25 m below water table) to the total yield of the wells will reduce significantly with increasing length of the cased portion of the wells. This reduction is even more pronounced if the aquifer has a vertical anisotropy (higher horizontal permeability compared to vertical permeability), in which case water can flow freely in a horizontal direction but the vertical flow is greatly retarded.
·
A slight increase of the horizontal permeability with depth (less than one order of magnitude) significantly reduces the contribution of the shallower layers to the total yield, in particular with increased length of casing. Individual layers of high permeability strongly influence the distribution of the contributing layers, in particular if the open section of the well crosses it or is very close.
·
40
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
·
A strong vertical anisotropy significantly reduces the height of the aquifer that contributes to the total yield (Water Authority 1995).
As the results of the preliminary groundwater model showed that it was feasible to install the well-field within the Lower Valley freshwater lens area it was decided to carry out a geological investigation to obtain more specific information on the aquifer. Accordingly, an exploratory deep well was drilled at Lower Valley so that the subsurface geology could be examined in detail, and the subsurface waters could be sampled and analyzed. The geological succession found in the well at Lower Valley was interpreted in the context of the geological framework of the island (Figs. 1, 3 and 4), which is well known through detailed studies of surface exposures and other wells (e.g., Jones 1994).
41
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Figure 3. Stratigraphic column for the Cayman Islands showing the consistent formations, their lithology, fossils, and style of fossil preservation (Jones 1994).
42
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
A
Ironshore Formation Pedro Castle Formation Cayman Formation LV#1 Well Location
HHS#1
19-82LV OWP#1A
N
18-82LV
Newlands
OWP#2
27-82LV Spotts
LV#2
SBQ
24-82LV
NE HHS#1A
Water Lens
OWP#1A
Lower Valley 18-82LV
+10
Pedro Castle Quarry
19° 16'N Beach Bay
OWP#2
SW
Great Pedro Point 81°18'W
24-82LV
B
Little Pedro Point
1
LV#2 27-82LV
km
Savannah
PCQ
0
Lower Valley Pedro Castle Quarry
19-82LV
High Bluff
Meters
0 -10
Cayman Unconformity
-20 -30
To 155 m
Figure 4 (A) Map of area around Lower Valley showing surface geology, location of Pedro Castle Quarry, and location of wells used to construct cross-section shown in Figure B. (B) Southwest to northeast cross section through Lower Valley showing architecture of the formations, location of the Cayman Unconformity, and location of Lower Valley water lens.
43
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Methods for Geological Investigation In 1996, a 150 mm diameter exploratory well (LV#2) was drilled to a depth of 122 m (Fig. 4). In 1997, that well was deepened to 152 m so that more information could be obtained on the subsurface geology of the area. In 1996, 1.5 m cores were obtained every 4.5 m from the top of the Cayman Formation (24.4 m) to a depth of 122 m (Fig. 5). Well-cuttings were obtained from the intervals between the cores until circulation was lost below 82 m (Fig. 5). The porosity and permeability of selected samples from the cores were obtained by the helium injection method. The composition of the rocks was determined by hand sample analysis, thin-section analysis, and scanning electron microscope analysis. Detailed geochemical analyses, which have been obtained for samples from this well, are not reported in this paper because they are not germane to the issue being considered herein.
Geology of Grand Cayman The central part of Grand Cayman is formed of dolostones and limestones that belong to the Bluff Group (Jones 1994). This group is formed, in ascending order, of the Brac Formation (Oligiocene), the Cayman Formation (Middle to Upper Miocene), and the Pedro Castle Formation (Pliocene) (Fig. 3). The Bluff Group is surrounded by and partly onlapped by the Ironshore Formation that is formed of limestones which were deposited during the Pleistocene (Vézina et al. 1999). The Brac Formation, named for a succession of dolostones and limestones found on the east end of Cayman Brac (Jones et al. 1994), is not exposed on the surface of Grand Cayman. The overlying Cayman Formation, widely exposed on the eastern half of Grand Cayman (Fig. 1), is formed entirely of finely crystalline white to off-white dolostones. It contains numerous fossils including a diverse biota of corals, red algae, bivalves, foraminifera, and gastropods. Any skeletal components originally formed of aragonite were dissolved during early diagenesis and are now represented by fossil-mouldic porosity. The Pedro Castle Formation, which is found mainly on the western part of Grand Cayman (Fig. 1), is formed of fossiliferous limestones, dolostones, and variably dolomitized limestones. There is no systematic distribution to the dolomite in this formation. As in the Cayman Formation, fossil-mouldic porosity is common. The Ironshore Formation is formed of friable, highly fossiliferous limestones that are largely formed of aragonite (Vézina et al. 1999). No dolomite has been found in this formation. Well-preserved corals, bivalves, gastropods, algae, and foraminifera are common in these strata. None of the fossils have been dissolved. The subsurface geology of Grand Cayman is complex and it is commonly difficult to correlate successions from different parts of the island because (1) the boundaries between successive formations are unconformities that are commonly characterized by substantial relief, and (2) the rock types in each formation are very similar and intra-formation correlations are virtually impossible. For example, the Cayman Unconformity that separates the Pedro Castle Formation from the underlying Cayman Formation has a relief of at least 40 44
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
m (Jones and Hunter 1994). This unconformity is a physical record of the rugged karst topography that developed on Grand Cayman at the end of the Miocene (~ 5 million years ago) when sea-level was at least 40 m below present-day sea-level (Jones and Hunter 1994). This is a critical boundary because the characteristics of the underlying Cayman Formation appear to be intimately linked to the diagenetic processes that took place when that erosional land surface was formed.
Geology of the Lower Valley Area The geological framework of the Lower Valley area has been established by examination of all surface outcrops, cores and well cuttings from this area (Fig. 4). Compared to most of Grand Cayman, this area is geologically complex because (1) there is significant relief on the Cayman Unconformity, and (2) partly as a result of the relief on the Cayman Unconformity, there are complex vertical and lateral relationships between the Cayman Formation, Pedro Castle Formation, and Ironshore Formation (Fig. 4). The upper part of the Cayman Formation, the Cayman Unconformity, and the Pedro Castle Formation are well exposed in Pedro Castle Quarry, which is located on the south coast of Grand Cayman (Fig. 4A). There, the Cayman Unconformity, which dips at 1-2° to the northwest, is located ~ 10 m above sea-level (Fig. 4B). In LV#2, which is located ~1 km northeast of Pedro Castle Quarry, the Cayman Unconformity is 24.4 m below sea-level (Fig. 4B). Thus, there is ~ 35 m of relief on the Cayman Unconformity over a distance of ~ 1 km. In well LV#1, located about 100 m to the north of LV#2, the boundary is ~ 30 m below sealevel. Thus, between LV#1 and LV#3, there is ~ 6 m of relief on the Cayman Unconformity. The Cayman Formation is divided into the informally named “cap rock” and “porous unit” (Fig. 5). The cap rock is typically ~ 15 m thick. Located immediately below the Cayman Unconformity, it is formed of very hard finely crystalline dolostones that are characterized by low porosity (< 10 %) and low permeability. The underlying porous unit is formed of friable, finely crystalline dolostones that are characterized by high porosities (35-40%) and locally, high permeability (Fig. 5). The location of cap rock is critical to any assessment of reservoir conditions. The cap rock is present irrespective of the elevation of the Cayman Unconformity. Thus, it appears to be product of diagenesis associated with the formation of the unconformity rather than an original depositional unit. Geological Succession in Well Lv#2 Well LV#2 penetrated the Ironshore Formation (0-8.5 m), the Pedro Castle Formation (8.524.4 m), the Cayman Formation (24.4-121.9 m), and the Brac Formation (121.9-155.4 m) (Fig. 5). The matrix porosity of the finely crystalline dolostones in the Cayman Formation, which is 948% (Fig. 5), is formed of small (< 20 µm) intercrystalline pores and hollow dolomite rhombs. Locally, the total porosity of the dolostones is increased by the presence of fossilmouldic cavities (after corals, bivalves, gastropods), fissures, and caves. In the LV#2 well there are two significant sets of caves, one from 82 to 86 m and one from 94 to 96 m (Fig. 5). 45
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
These caves have a significant affect on water circulation in the area. For example, once the drill bit had passed through the caves from 82-86 m water no longer returned to the surface and it was therefore no longer possible to collect well cuttings from the lower part of the Cayman Formation (Fig. 5). Clearly, the caves mark a significant change in the subsurface properties of the Cayman Formation. The permeability of the finely crystalline dolostones in the Cayman Formation is typically below 2,500 mD (Fig. 5). In the 45 to 62 m interval, however, the horizontal and vertical permeabilities are up to ~ 10,000 mD (Fig. 5). The “cap rock” in the Cayman Formation is characterized by low porosity (< 10 %) and low permeability (Fig. 5). Of particular importance is the fact that the vertical permeability in the cap rock is at or close to zero (Fig. 5). The underlying porous unit can be divided in to two parts according to its porosity and permeability characteristics. The upper part of the porous unit (~45 to 62 m), located immediately under the cap rock, is formed of dolostones with high porosity (>35%) and high permeabilities (Fig. 5). The lower part of the porous unit is formed of dolostones with high porosity (> 35%) but low permeability (Fig. 5). The underlying geological reasons for the difference in the permeabilities of the dolostones in the lower and upper parts of the porous unit are unknown. Large caves are found in the lower part of the porous unit (Fig. 5).
46
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Figure 5. Stratigraphic column for well LV#2 showing location of cores (black), core numbers, intervals from which well cuttings were collected (shaded), and porosity and permeability trends.
47
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
Discussion On Grand Cayman, the Cayman Formation and Pedro Castle Formation are formed of highly porous and permeable dolostones. Locally, the porosity and permeability is accentuated by the presence of fossil-mouldic cavities, fissures, and caves. As a result, the aquifers on Grand Cayman are unconfined and virtually impossible to model on a consistent basis. The complexity of the aquifer is increased by the fact that the low porosity, low permeability cap rock of the Cayman Formation is genetically linked to the Cayman Unconformity, which is characterized by significant relief. Accordingly, well-field designs must rely on site-specific information if they are to be successful. At Lower Valley, the abstraction zone was located at 45 – 65 m for the following reasons: · This zone is formed of finely crystalline dolostones that are characterized by high porosity and high horizontal and vertical permeabilities (Fig. 5). · This zone is overlain by the cap rock of the Cayman Formation, which is formed of finely crystalline dolostones that have low porosity and low permeability (Fig. 5). The very low vertical permeability of these dolostones meant that the probability of any connection between the abstraction zone and the freshwater lens was very low. In effect, the cap rock acts as a very effective barrier that isolates the freshwater lens from the saline water found at greater depths. · The dolostones immediately beneath the abstraction zone are characterized by low permeability despite their high porosity (Fig. 5). · Initial tests indicated sustained abstraction could be maintained from this zone without any problems. The disposal zone was located at 62 - 86 m for the following reasons: · Large caves and cavities characterized the lower parts of this zone. The loss of circulation while drilling through this zone indicated that this was a highly transmissive zone that was capable of absorbing vast quantities of fluid. · The upper part of the disposal zone, from 62 - 82 m, is formed of finely crystalline dolostones with very low horizontal and vertical permeability. Thus, there the probability of dense brines being able to migrate vertical upwards into the abstraction zone appeared to be very low.
48
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands 0
Ironshore Formation
10
Pedro Castle Formation
20
Cayman Unconformity
Cap Rock
30 40
Cayman Formation
Meters below sea level
50 60 70 80
Cavities 90
Abstraction Zone
Disposal Zone
Porous Unit
Cavities 100 110 120 130
Brac Formation
140 150
Figure 6. Schematic diagram of Lower Valley area showing locations of abstraction and disposal zones relative to the geological succession.
49
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
The well-field consists of 2 abstraction wells and 1 brine disposal well. The horizontal separation between the abstraction and disposal wells is approximately 110 m; the open zone in the abstraction well is from 45 to 65 m whereas the open zone in the disposal well is from 62 to 86 m (Fig 6). During construction of the wells ultimate care was taken to ensure that no large quantities of saline water were disposed on the fresh water lens and that the well casing was properly installed and grouted. Prior to the installation of these wells the air rotary method was always used in the Cayman Islands to drill wells; however, continued use of that method would have resulted in the disposal of large volumes of saline water on the Lower Valley lens. Thus, Industrial Services and Equipment Ltd., the local well drilling company that was awarded the contract, carried out the drilling using the reverse air rotary method in order to minimize the volume of saline water that was disposed on the lens. ;’ The ultimate test of any well-field design is its successful implementation and its subsequent operation through time. The reverse osmosis water plant became operational in March 1998 with the abstraction of 3,750 m3/day of saline water from one abstraction well. On a daily basis this produced 1,500 m3 of fresh water for drinking and 2,250 m3 of brine for disposal. In 1999, the production capacity was doubled by additional abstraction of 3,750 m3/day from a second well. This produced 3,000 m3/day of freshwater and 4,500 m3/day of brine. These production levels have been constantly maintained and no problems have been encountered in the abstraction of the saline water or the disposal of the brines. Such efficient productivity clearly indicates that the system is operating as it was designed. One of the prime mandates in the construction and operation of the reverse osmosis plant at Lower Valley was that it should have no impact on the existing fresh water lens that is still used by surrounding farms and residences. Accordingly, a network of 25 shallow monitoring wells was established around the Lower Valley reverse osmosis plant to monitor the quality of the fresh water lens on an ongoing basis. These wells are located within a radius of 200 m from the plant with depths varying between 2.5 m to 12.4 m below the groundwater table (Water Authority 1997). Water quality data have been collected from these wells since September 1997, 6 months prior to the inception of the reverse osmosis plant, to date. These data clearly demonstrate that there has been no degradation of the water quality in the Lower Valley lens (Fig. 7). Groundwater quality is influenced by rainfall and consequent recharge of the lens, this is shown by fluctuations in Electrical Conductivity of the groundwater in the piezometer. Electrical Conductivities increase during the dry season (December-June) when recharge is limited and decrease during the wet season when recharge increases (JuneNovember) (Fig 7). Furthermore the Electrical Conductivity of the feedwater of the reverse osmosis plant has remained constant throughout the lifetime of the plant, this is a strong indication that the hyper saline brine does not migrate towards the abstraction wells. This evidence further underlines the success of the well-field design.
50
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands 7.0 Piezometer depth below mean sea level
3.4m
6.0
5.7m
8.7m
EC (mS/cm)
5.0
4.0
3.0
2.0
1.0
0.0 Sep 97
Mar 98
Sep 98
Mar 99
Sep 99
Mar 00
Sep 00
Mar 01
Figure 7. Electrical Conductivity in the open zone of 3 piezometers from September 1997 – August 2001. Conclusions The Water Authority-Cayman has successfully designed a well-field for the reverse osmosis plant located over a freshwater lens in Lower Valley. Operational data from the plant and data obtained from wells specifically installed to monitor the effects of the plant on the shallow freshwater lens indicate that the abstraction of saline groundwater and the disposal of brine have not resulted in adverse impacts on the freshwater lens. In designing the well-field careful consideration was given to the potential negative effects that this project could have on local groundwater conditions. Initially a preliminary groundwater model was established to determine under what conditions the well-field design would be successful, however due to lack of actual site specific data it was decided to carry out a geological investigation of the site. This geological investigation produced a wealth of data that supported the feasibility of the project. Careful installation and grouting procedures of the abstraction and disposal wells were crucial to ensure that feedwater is abstracted and that brine is disposed in suitable zones. The project’s success has been verified by monitoring of groundwater conditions of the shallow freshwater lens. It is crucial to realize that none of the elements of groundwater modeling, geological investigation, installation and groundwater monitoring in isolation would be sufficient to design a well-field that does not adversely impact the shallower fresh water lens.
51
Well-Field Design for a Saltwater Reverse Osmosis Plant located over a Fresh Water Lens in Lower Valley, Grand Cayman, Cayman Islands
References Cayman Islands Census (1999) Report of the Cayman Islands 1999 population & housing census. Government of the Cayman Islands. Jones, B. (1994) Geology of the Cayman Islands. In Brunt, M.A., and Davies, J.E., eds., The Cayman Islands: Natural History and Biogeography. Dordrecht, The Netherlands, Kluwer, pp. 13-49. Jones, B., and Hunter, I.G. (1994) Messinian (Late Miocene) karst on Grand Cayman, British West Indies: an example of an erosional sequence boundary. Journal of Sedimentary Research, Vol. 64, pp. 531-541. Ng, K.-C. (1990) Diagenesis of the Oligocene-Miocene Bluff Formation of the Cayman Islands – a petrographic and hydrogeochemical approach. Unpublished Ph.D. Thesis, University of Alberta, Canada, 344 p. Ng, K.-C., Jones, B., and Beswick, R. (1992) Hydrogeology of Grand Cayman, British West Indies: a karstic dolostone aquifer. Journal of Hydrology, Vol. 134, pp. 273-295. Ng, K.-C., and Jones, B. (1994) Hydrogeochemistry of Grand Cayman, British West Indies: implications for carbonate diagenetic studies. Journal of Hydrology, Vol. 164, pp. 193216. Vézina, J., Jones, B., and Ford, D. (1999) Sea-level highstands over the last 50,000 years: evidence from the Ironshore Formation on Grand Cayman, British West Indies: Journal of Sedimentary Research, Vol. 69, p. 317-327. Water Authority (1994) Further development of piped water supply, technical report. Internal report, not published. Water Authority (1995) Construction of feed water and brine disposal wells at the Lower Valley facility. Internal report, not published. Water Authority (1997) Design and installation of network to monitor effects of reverse osmosis plant on the Lower Valley lens. Internal report, not published. Authors: 1 Brian Jones, Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada Tel: (780) 492-5249 Fax: (780) 492-8190 E-mail:
[email protected] 2
Hendrik-Jan van Genderen and Tom van Zanten Water Authority Cayman, P.O. Box 1104 GT, Cayman Islands Tel: (345) 949-6352 Fax: (345) 949-0094 E-mail:
[email protected]
52
Water Re-use Criteria & Health by Harry Philippeaux PAHO/WHO, Barbados, W.I. Abstract An essential goal in water reuse is to protect public health while maximizing the benefit of this resource. Wastewater, by its very nature, is a highly contaminated water source. A wide array of pathogens and organic and inorganic materials must be removed from the wastewater prior to indirect potable applications; for non-potable applications, only pathogens and some inorganic materials need to be removed. Water supply professionals should work closely with regulators and public health officials responsible for providing guidelines and standards to implement the level of reuse a community decides is appropriate. Reliance on existing drinking water standards alone to define safe indirect potable reuse is not sufficient. The drinking water community has applied a combination of source protection, drinking water standards, and optimal treatment to assure the safety of a particular water supply for drinking water purposes, assuming that in most cases the best available water sources would be used. These concepts need to be reevaluated in the context of any particular indirect potable reuse proposal. Research is needed to enable specific standards to be established for water supplies from impaired sources like reclaimed wastewater. Until more research is conducted into the range of contaminants and associated health effects of using reclaimed water as a drinking water source, a conservative approach in implementing indirect potable reuse must be taken. 1. Introduction Many communities face limitations in water supply because of temporary drought conditions or more permanent water allocation policies that split a finite and variable water supply among an increasing number of users. Environmental preservation and restoration has joined agricultural, municipal, and other interests in competition for limited water supplies Water reuse offers a reliable supply option, relatively unaffected by drought that a community can pursue at the local level. It conserves natural resources of supply and may offset the need for a more expensive, geographically remote, and environmentally disruptive alternative 2. Water Re-use Applications Reclaimed water has been successfully used for a wide range of applications. The various types of reclaimed water use are identified in Table 1. The acceptability of reclaimed water for any use depends on several factors, including the physical, chemical, and microbiological quality of the water. Depending on the intended use, considerations may include health protection, user requirements, irrigation effects,
53
Water Reuse Criteria & Health
environmental effects, aesthetics, and public and/or user perception of the reuse concept. Making reclaimed water suitable and safe is achieved by eliminating or reducing the concentrations of microorganisms and chemical constituents of concern through wastewater treatment and/or by limiting public or worker exposure to the water via design or operational controls. 3. Microbial Contaminants The potential transmission of infectious disease by pathogenic bacteria, protozoa, and viruses is the most common concern associated with nonpotable reuse of treated municipal wastewater. Sanitary engineering and preventive medical practices have combined to reach a point where waterborne disease outbreaks of epidemic proportions have, to a great extent, been controlled. However, the potential for disease transmission through the water route has not been eliminated. With a few exceptions, the disease organisms of epidemic history are still present in today’s sewage, and the status is more one of severance of the transmission chain than a total eradication of the disease agent. The potential spread of infectious diseases through water reuse remains a public health concern. 3.1 Presence and Survival of Pathogens - The occurrence and concentration of pathogenic microorganisms in raw municipal wastewater depend on a number of factors, and it is not possible to predict with any degree of assurance what the general characteristics of a particular wastewater will be with respect to infectious agents. These factors include the sources contributing to the wastewater, the general health of the contributing population, the existence of disease carriers in the population, and the ability of infectious agents to survive outside their hosts under a variety of environmental conditions. The occurrence of virus in municipal wastewater fluctuates widely. Virus concentrations are generally highest during the summer and early autumn months. Viruses as a group are generally more resistant to environmental stresses than many of the bacteria, although some viruses persist for only a short time in municipal wastewater. As a group, parasitic cysts maintain their viability for longer time periods in the open environment than either bacteria or viruses. Under favorable conditions, pathogens can survive for long periods of time on crops or in water or soil. While various pathogens exhibit a wide range of survival characteristics, environmental factors that affect survival include moisture content (desiccation generally adversely affects survival), soil organic matter content (presence of organic matter aids survival), temperature (longer survival at low temperatures), humidity (longer survival at high humidity), pH (bacteria survive longer in alkaline soils than in acid soils), amount or rainfall, amount of sunlight (solar radiation is detrimental to survival), protection provided by foliage, and competitive microbial fauna and flora. Survival times for any particular microorganism exhibit wide fluctuations under differing conditions. For example, at low temperatures some microorganisms can survive in the underground for months or years. Viruses have been isolated in groundwater after various migration distances by a number of investigators examining several recharge operations. Horizontal migration distances ranged from 3m (10ft) to more than 400m (1,300 ft) [Gerba an Goyal, 1985]. Depending on soil
54
Water Reuse Criteria & Health
conditions, bacteria and larger organisms associated with wastewater can be effectively removed by soil after percolation through as little as 8cm (3in) of the soil mantle. 3.2. Disease Incidence Related to Water Re-use Epidemiological investigations directed at wastewater-contaminated drinking water supplies, the use of raw or minimally-treated wastewater for food crop irrigation, health effects on farm workers who routinely come in contact with poorly treated wastewater used for irrigation, and the health effects related to aerosols on windblown spray emanating from spray irrigation sites using undisinfected wastewater have all provided evidence of infectious disease transmission from such practices [Lund, 1980; Shuval et al., 1986]. The majority of documented disease outbreaks have been the result of contamination by bacteria or parasites. Several incidences of typhoid fever were reported in the early 1900s, and a major outbreak of cholera in Jerusalem in 1970 was reportedly caused by food crop irrigation with undisinfected and salad crops with untreated wastewater in several countries. Human infection with the adult stage of the beef tapeworm Taenia saginata, due to ingestion of the cyst form, has resulted from irrigation of grazing land with raw and settled sewage. Evidence of tapeworm transmission via infected cattle and sheep in Europe, Australia, and elsewhere has been well documented [Sepp, 1971]. 4. Chemical Contaminants Health effects related to the presence of organic constituents are of primary concern with regard to potable reuse. In municipal wastewater, the chemical constituents are generally not a major health concern for urban uses of reclaimed water but may affect the acceptability of the water for uses such as food crop irrigation, industrial applications, and indirect potable reuse. Chemical constituents are a concern when reclaimed water percolates into potable groundwater aquifers as a result of irrigation, groundwater recharge, or other uses. Effects of physical parameters, e.g., pH, color, temperature, and particulate matter, and chemical constituents, e.g., chlorides, sodium, and heavy metals, are well known, and recommended limits have been established for many constituents. Both organic and inorganic constituents need to be considered where reclaimed water is utilized for food crop irrigation, where reclaimed water from irrigation or other beneficial uses reaches potable groundwater supplies, or where organics may bioaccumulate in the food chain, e.g., in fish-rearing ponds. The assessment of health risks associated with indirect potable reuse is not definitive due to limited chemical and toxicological data and inherent limitations in the available toxicological and epidemiological methods. On the basis of available information, however, there is no indication that health risks from using high quality reclaimed water (that has been subjected to advanced wastewater treatment processes for organics removal) for potable purposes are greater than those from using existing water supplies. 5. Water Reuse Criteria Water reclamation and reuse criteria are principally directed at health and environmental protection and typically address wastewater treatment, reclaimed water quality, treatment
55
Water Reuse Criteria & Health
reliability, distribution systems, and use area controls. Water quality criteria are based on a variety of considerations, including the following: ·
Public health protection: Reclaimed water should be safe for the intended use. Most existing water reuse regulations are directed principally at public health protection. For nonpotable uses of reclaimed water, most state regulations address only microbiological and environmental concerns.
·
Use requirements: Many industrial uses and some other applications have specific physical and chemical water quality requirements that are not related to health considerations. The physical, chemical and/or microbiological quality may limit user or regulatory acceptability of reclaimed water for specific uses.
·
Irrigation effects: The effect of individual constituents or parameters on crops or other vegetation, soil, and groundwater or other receiving water should be evaluated reclaimed water irrigation applications. Environmental considerations: The reclaimed water should not adversely impact the natural flora and fauna in and around reclaimed water use areas and receiving waters.
· ·
Aesthetics: For high level uses, e.g., urban irrigation and toilet flushing, the reclaimed water should be no different in appearance than potable water, i.e., clear, colorless, and odorless. For recreational impoundments, reclaimed water should not promote algal growth.
There has been very little effort made until today in the world to regulate the consumption of water reuse. In North American jurisdictions, there are no federal standards or regulations governing water reuse. The U.S. Environmental Protection Agency (EPA) published Guidelines for Water Reuse in 1992 that address many aspects of water reclamation and reuse and include recommended criteria for various types of water reuse. For indirect potable reuse, however, requirements are typically established on a case-by-case basis. Indirect potable reuse systems presently in operation include treatment barriers and operational strategies to provide the required level of safety and reliability determined by the water supply utility and state and local regulators. Safety and reliability features can make these systems expensive. These EPA guidelines suggest that, regardless of the type of reclaimed water use, some level of disinfection should be provided to avoid adverse health consequences from inadvertent contact with reclaimed water or accidental or intentional misuse of a water reuse system. For nonpotable uses of reclaimed water, only two different levels of treatment and disinfection are recommended. Reclaimed water used for applications where no direct or indirect public or worker contact with the water is expected should receive at least secondary treatment and be disinfected to achieve a fecal coliform concentration not exceeding 200/100 mL.
56
Water Reuse Criteria & Health
6. Summary Making reclaimed water suitable and safe for reuse applications is achieved by eliminating or reducing the concentrations of microbial and chemical constituents of concern through wastewater treatment and/or by limiting public or worker exposure to the water via design and operational controls. Factors that affect the quality of reclaimed water include source water quality, wastewater treatment processes and treatment effectiveness, treatment reliability, and distribution system design and operation. Most states require implementation of industrial source control programs to limit the input of chemical constituents that may adversely affect biological treatment processes and subsequent acceptability of the water for specific uses. Assurance of treatment reliability is an obvious, yet sometimes overlooked, quality control measure. Distribution system design and operation is important to assure that the reclaimed water is not degraded prior to use and not subject to misuse. For example, open storage may result in water quality degradation by microorganisms, algae, or particulate matter, and cause objectionable odor or color in the reclaimed water. Table 1. Uses of Reclaimed Water Category of Use Landscape irrigation Agricultural irrigation Nonpotable urban uses (other than irrigation) Industrial uses Impoundments Environmental uses Groundwater recharge Potable water supply augmentation (indirect potable reuse) Miscellaneous
Specific Types of Use Parks playgrounds, cemeteries, golf courses, roadway rights-of way, school grounds, greenbelts, residential and other lawns Food crops, fodder crops, fiber crops, seed crops, nurseries, sod farms, silviculture, frost protection Toilet and urinal flushing, fire protection, air conditioner chiller water, vehicle washing, street cleaning, decorative fountains and other water features Cooling, boiler feed, stack scrubbing, process water Ornamental, recreational Stream augmentation, marshes, wetlands, fisheries Aquifer storage and recovery, salt water infusion control, ground subsidence control Groundwater recharge, surface water augmentation Aquaculture, snow-making, soil compaction, dust control, equipment washdown, livestock watering
57
Water Reuse Criteria & Health
Table 2. U.S. EPA Guidelines for Water Reuse Reclaimed Water Quality Urban uses, crops eaten raw, recreational impoundments
Restricted access area irrigation, processed food crops, nonfood crops, aesthetic impoundments, construction uses, industrial coolingd, environmental reuse Groundwater recharge of nonpotable aquifers by spreading Groundwater recharge of nonpotable aquifers by injection Groundwater recharge of potable aquifers by spreading Groundwater recharge of potable aquifers by injection, augmentation of surface supplies
a
b c d e
Type of Use § § §
§ §
Secondary Filtration Disinfection
Secondary Disinfection
§
Site specific and use dependent § Primary (minimum) § Site specific and use dependent § Secondary (minimum) § Site specific and use dependent § Secondary & disinfection (minimum) Includes the following: § Secondary § Filtration § Disinfection § Advanced wastewater treatment
Treatment § § § § §
PH=6 – 9 ≤10 mg/L BOD ≤2 NTUa No detectable fecalColi/100 mLb ≥1mg/L Cl2 residualc
§ § § § §
PH=6 – 9 ≤30 mg/L BOD ≤30 mg/L TSS ≤200 fecal coli/100 mLe ≥1mg/L Cl2 residual
§
Site specific and use dependent
§
Site specific and use dependent § Site specific § Meet drinking water standards after percolation through vadose zone Includes the following: § PH=6.5 - 8.5 § ≤2 NTU § No detectable fecalColi/100 mLb § ≥1mg/L Cl2 residualc § Meet drinking water standards
Should be met prior to disinfection. Average based on a 24-hour time period. Turbidity should not exceed 5 NTU at any time. Based on 7-day median value. Should not exceed 14 fecal coli/100 mol in any sample. After a minimum contact time of 30 minutes. Recirculating cooling towers. Based on 7-day median value. Should not exceed 800 fecal coli/100 mL in any sample.
Harry Philippeaux, PAHO Environmental Health Advisor PAHO/WHO – Office of Caribbean Program Coordination P.O. Box 508, Bridgetown, Barbados, W.I. Tel: (246) 420-8058 Fax: (246) 436-9779 E-mail:
[email protected] 58
Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment. by R.. A. Bisson, Earthwater Technology, Trinidad & Tobago, R. B. Hoag, J.C. Ingari, Earthwater Technology, Trinidad & Tobago and HydroSource Associates, Inc. U.S. Maharaj, L. Jadoo, Water and Sewerage Authority of Trinidad & Tobago Abstract The modern concept of “megawatershed” as a paradigm for groundwater occurrence has recently been systematically and objectively tested through an integrated, island-wide groundwater reassessment and water well development project on the island of Tobago. Long-term monitoring of production wells resulting from the 1999-2000 pilot project provided the Water & Sewerage Authority of Trinidad & Tobago (WASA) with the opportunity to calibrate megawatershed recharge to local aquifers and to compare megawatershed exploration programme results with previous attempts to discover groundwater using traditional watershed concepts and conventional exploration methods. The project was carried out on the Island of Tobago in 1999-2000 and was unprecedented in the Caribbean. Previous estimates of sustainable groundwater availability using “traditional” watershed concepts and groundwater assessment methods were computed to be 0.69 MCM/Year. Reassessment of sustainable groundwater availability using the megawatershed method revealed approximately two orders of magnitude more water available for safe withdrawal, at 66 MCM/Year. Subsequent long-term test pumping results from high-yield bedrock wells drilled into several of these newly identified megawatersheds confirmed safe yield projections. Key Words Megawatershed, Groundwater, Recharge, Exploration, Tobago, Assessment
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Introduction to Megawatersheds Paradigm For over a decade, hydrogeologists have successfully employed the “megawatersheds” concept of groundwater occurrence to discover and develop large quantities of previously undetected groundwater for numerous government and private water utilities (Enron International, Inc. 1997). Despite the substantial body of evidence and long track record of achievement, the megawatershed paradigm continues to elicit scepticism from water engineers and traditional hydrologists, and water-short public utilities remain resistant to the idea that very large, local sources of sustainable fresh water might have been overlooked by numerous expert groups using generally accepted hydrogeological concepts and groundwater exploration methods. History: The megawatershed paradigm, or model, is a modern, geology-based concept of groundwater environments, which has ancient roots, but could not be adequately understood and substantiated using “the scientific method” until the availability of space-age technologies. These technologies include earth observation satellites and geographic information systems (GIS), combined with the advent of modern geological concepts, especially plate tectonics, enabling hydrogeologists to objectively re-evaluate the Earth’s water resources. Documentation of groundwater occurrence in deep bedrock mines and wells extends thousands of years into history. Examples of this phenomenon include deep groundwater infiltration forcing the closing of ancient Egypt’s’ hand-dug gold mines (Page, L.R., 1983) to the constant de-watering required in present day South Africa’s kilometres-deep shafts and Nevada’s open pit excavations (Stone et al., 1991). In modern times petroleum geologists and other deep well drillers have documented fresh water discoveries at depths exceeding 3 kilometres in fractured rocks (Magaritz, et al., 1990, Burbey, T.J. and Prudie, D.E., 1991, Huntoon, P.W.,1986, Moore, W.S., 1996, Simmons, G.M.,1992). Since little was known about the regional geometry, hydraulic conductivity and connectivity of bedrock fault and fracture zones, and the paucity of worldwide rainfall and evapotranspiration data, hydrologists conservatively concluded that deep groundwater sources were principally “fossil” in nature, disconnected from active surface recharge and of unknown, ancient origin (USGS, 1998, Gleick, P.H, 1993). These assumptions have historically been applied to water resource evaluations of the world’s great groundwater catchments, from Egypt’s immensely thick sandstone and carbonate basins to the equally vast Great Carbonate Basin of the western USA. Since the 1970’s and 80’s advent of modern earth observation satellites and general acceptance by the world community of earth scientists of plate tectonics as valid scientific theory, geologists have commenced using tectonic models and satellite imagery to map tectonically-induced crustal fracturing for a variety of practical purposes, including economic recovery of oil, gas, minerals and more recently, deep groundwater. Modern investigators have found evidence of many types of tectonically-related deep groundwater occurrence, from paleowaters slowly flushed through the Earth’s porous and fractured crust by continental-scale tectonics over millions of years (Person, et al., 1996) to active introduction of modern meteoric waters in the upper one (1) kilometre of fractured bedrock (USDOE,
60
Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
1998). Other scientific papers and reports added credence to the thesis that deep, regional, inter-basin and coastal groundwater flow systems demonstrated active regional recharge, but did not address specific origins, pathways, or seek to quantify potential recharge (USGS, 1991, Driscoll, N., 1997, Church, T.M., 1996, Falkowska, L.,1998, Mirecki, J.E. and Manheim, F.T.,1998). Recharge Mechanisms Discovered: In the mid-1980’s, investigators working in East Africa for USAID first correlated regional tectonic frameworks with hydraulically conductive fracture geometries and groundwater occurrence and subsequently performed detailed studies of Northwest Somalia and the coastal region of Sudan that addressed specific attributes of inter-basin, fractured bedrock groundwater flow systems such as fracture geometries, conductivities, catchment and recharge (Bisson, R.A., et al., 1990). The term “megawatershed” was formally introduced into the lexicon of hydrogeological terms in 1989 and 1990 publications describing the East Africa Rift related groundwater phenomena (Bisson, R.A.,1989, Bisson, R.A. and El-Baz, F., 1990) (Figure 1). The original investigators’ integrated, systematic approach to megawatersheds exploration became known as the “Megawatersheds Exploration Programme” (Figure 2). However, until the Tobago Project was launched, there were no known existing case studies involving complete hydrological systems that quantitatively compare results from actual applications of the “megawatersheds” paradigm of deep groundwater occurrence and the traditional “watershed” concept of sedimentary aquifers.
Figure 1. Conceptual Megawatershed model
61
Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Figure 2. Illustration of Megawatershed Exploration Programme
Tobago Megawatersheds Assessment & Development Project Background Thirty years of prior groundwater exploration and drilling work performed by several consultants on the Island of Tobago employed traditional concepts and focused on aquifers in alluvial deposits, with results limited to three (3) alluvial wells producing 0.05 MGD to 0.10 MGD per well and predicted sustainable yields totalling 0.69 MCM/Year. All alluvial wells tested at higher pumping rates exceeded their recharge limits and could not be sustained. In 1999 an independent consultant performed for WASA an extensive review and summary of results from all prior hydrogeological studies of Tobago, all of which employed traditional watershed concepts (DHV Consultants BV, et al., 1999). WASA then pursued alternative methods of groundwater exploration using a novel-contracting concept (Maharaj, U.S., 2000) and executed a reassessment of the hydrogeology and hydrology of the island with a consultant employing the “megawatersheds” concept. That project was completed in July 2000 (Earthwater Technology International, Inc., 2000). A comparison of results from prior “watershed” studies and the new “megawatershed” approach to new water development in Tobago is presented in this paper. As described in the introduction above, several independent investigators working at varied venues, ranging from the Andes Mountains (Magaritz, A.M., et al., 1990) to the Nevada desert (Burbey, T.J. and Prudic, D.E., 1991), have documented Megawatershed environments. The Tobago exploration team previously identified megawatersheds over much of the globe, including the hyper-arid Red Sea province of North Sudan (40 million gallons per day), the desert in northwest Somalia (20 million gallons per day) and over 200
62
Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
water wells drilled in New England’s normally low yielding metamorphic and igneous rocks producing 100,000 to 500,000 gallons per day. Island Of Tobago Tobago is the smaller of the twin island Republic of Trinidad and Tobago. The republic is the southern-most of the chain of Caribbean islands of the Lesser Antilles. It is located just north of Venezuela’s coastline. Tobago sits off the northeast extremity of Trinidad. The island physiography is characterized by a southwest to northeast trending mountain ridge for over two-thirds of the western part and the minor part in the eastern portion characterized by a low-lying flat lands. Its size is 300 square kilometres, with a year round population of 55,000 in 2000. Tobago (Figure 3) is an island exposure that forms part of a structural high comprising predominately Mesozoic igneous and metamorphic rock. It resides at the northeastern most corner of the present day South American continental shelf. These rocks can be divided into four main groups, which form approximately East-West-striking belts that transect the island. Younger Cenozoic sedimentary deposits consist of clays, silts, sandstones, gravels and an even younger platform of coralline limestone. Brittle faults of variable slip delineate several fault systems that have fragmented the Mesozoic belts of the island. In addition to the largescale fault systems with associated offsetting lithologies, the island is pervasively fractured by faults of all scales.
Figure 3. Tobago Location and Generalised Geology
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Due to its large expanses of beaches, coral reefs, rain forests, stable and friendly environment and tropical weather, the main activity is centred on tourism. The major human development is located within the low-lying areas of the Southwest and along the Southern coast of the island. The main hub of tourism is in the Southwest. The island’s climate is characterized by typical tropical weather patterns, with a dry season spanning from January to May and a rainy season from December to June. Rainfall during the dry season averages 55 inches and 110 inches during the rainy season. The overall water availability of the island was computed to be 29,920 million gallons per year, which if expressed on a per capita basis yields a value of 534,600 per year. This value, if compared to the World Bank’s standards, indicates that the island cannot be classified as a water scarce country having a per capita availability of over 22,000 gallons per year. The problem of water supply is not due to the overall availability, but due to the extreme spatial and seasonal availability on the island. Tobago’s Water Supply Deficit: The water supply system on the island is owned by the Government and is managed by the Water and Sewerage Authority (WASA). The estimated demand on the island in the year 2000 was 7.5-8.5 million gallons per day. Demand calculations used a per capita consumption of 70 gallons per day and an estimate of unaccounted-for-water of 45-55%. The water supply deficit, not catering for supply bottlenecks, was estimated at 2.0-2.5 million gallons per day. Over the last few years the island had been experiencing extreme water demand shortfalls that were hampering its tourism based economic development. Apart from the nominal water deficit, which mandated the rationing of water for domestic consumption and tourism, there were both dry season and rainy season problems that would further aggravate the situation. Low flows and excessive drawdown of the island’s only reservoir during the dry season reduced water production. This is exemplified in Figure 4 for the severe dry season in 1998 and 2001. In the wet season, during periods of heavy rainfall, high levels of siltation caused surface water intakes to completely shut down, since they were not equipped to treat these excessive turbidity levels. Oftentimes, water production of less than 3.0 million gallons per day had to be rationed to customers. The Year 2000 Groundwater Reassessment and Development Project The Year 2000 project targeted “megawatersheds” in the island’s underlying bedrock, comprised of igneous and metamorphic rocks, as a source of freshwater for the island. The project required that the hydrogeology of the island be reassessed using the megawatershed paradigm to map the recharge areas and that the most favourable locations within megawatersheds proximal to WASA’s distribution system be identified, test-drilled and put into production for highest benefit/cost to the consumer. This required that the consultant accurately determine the full groundwater recharge, storage and transmission potential of the island and each target zone. Development of a minimum of 2.0 MGD (over 4.0 MGD was actually drilled and tested) in selected areas depending upon the distribution of consumer demands on the island.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
HILLSBOROUGH PRODUCTION GRAPH 1995 - 2001
11,000
10,000
9,000
PRODUCTION M3/D
8,000
7,000
6,000
5,000
4,000
3,000
2,000
OCT
JUL
APR
Jan-01
OCT
JUL
APR
YEAR
Jan-00
OCT
JUL
APR
Jan-99
OCT
JUL
APR
Jan-98
OCT
JUL
APR
Jan-97
OCT
JUL
APR
Jan-96
OCT
JUL
APR
Jan-95
REC. PRODUCTION M3/D
DENOTES DRY SEASON DENOTES W ET SEASON
Figure 4. Five-Year Monthly Production Levels at Hillsborough Dam.
The drilling of water wells within six (6) different megawatersheds provided enough information to allow an assessment of the accuracy of the megawatershed models. This was accomplished by comparing predictions of aquifer recharge with the measured results of the safe yields over a twelve (12) month period. Overview of Tobago Megawatersheds Exploration Programme The technology employed in the reassessment of the groundwater potential of the island and the mapping of megawatersheds involved a combination of satellite data, aerial data, ground surface testing and sub-surface investigations as shown in Figure 2. These discrete data sets when analysed in an integrated manner were used to target areas within the complex network of fractures and faults (lineaments) pervasive on the island. The following is a summary of the techniques employed: §
§ § §
Thematic Mapper Imagery acquired from the LandSat satellite was processed with proprietary three-band and six-band techniques allowing for the characterization of structural features and mapping of lithologic units in areas of limited vegetative cover. Satellite was used to discern topographic features and surface roughness to differentiate rock types through vegetative cover. Aerial Magnetic Surveys obtained from oil companies allowed determination of the mineralogy of rock types for lithological characterization. Aerial Photographs yielded 3-D views of the island’s surface to infer the presence of lineaments and fractures.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
§ § § § §
Digital Elevation Model data manipulated by changing vertical exaggeration, sun angle and azimuth yielded information on the linear and geomorphic features on the earth’s surface. GIS Integration of the diverse forms of data and interpreted information was used as the base for overlying diverse data sets allowing for superior definition of the fracture fabric system of the island. The presence of implied fracture zones and faults were verified by field surveys. Geophysical surveys such as, resistivity, magnetic, electromagnetic and gravimetric sub-surface investigations allowed the determination of geologic structure and the presence of fresh water. Hydrological modelling was used to determine the amount of groundwater infiltration into the extensive fracture network of the postulated megawatersheds.
Expert interpretation of this data in addition to an in-depth understanding of the regional and local tectonics is the key to determining the presence of bedrock aquifers, the extent of the megawatershed, the exact location of the aquifer and the recharge into the aquifer. Recharge Calculations Critical to the computation of the safe-yield of an aquifer or water well is the determination of the groundwater recharge computed from the equation: Recharge = Precipitation – Evapotranspiration – Run-Off As described by Hoag, et al. (2000), it was necessary, due to limited data, to develop relationships between the hydrological parameters for which data was available. A consistent proportional relationship was established between precipitation and evapotranspiration at a single location and between precipitation and run-off for data at several watersheds on the island. These relationships were applied to the 30-year isohyetal map available for the island such that a recharge contour map of the entire island was developed. The recharge map is shown in Figure 5. Also shown in the figure is the topographic expression of the island into minute sub-basins, i.e. Groundwater Recharge Units (GRU’s), into which recharge can be computed either for traditional or megawatershed aquifers by overlay and integration with ArcView. The approximately one (1) square kilometre GRU’s were delineated using a proprietary software package. The megawatershed-model aquifers were delineated through an analysis of the fracture architecture of the island in conjunction with the distribution of GRUs. Where implied fracture zones cross major watershed boundaries, the recharge to GRUs adjacent to these fractures are summed in order to estimate the recharge to the Megawatersheds. The result of this analysis is shown in Figure 6. Megawatersheds in which production wells were developed are labelled. The delineated alluvial aquifers for the island are also shown in Figure 7. Recharge to the alluvial aquifers is constrained by GRUs adjacent to and topographically up gradient of the alluvium. The recharge of the alluvial systems contained within megawatersheds is also presented in Table 1. The differences between traditional and megawatershed recharge is huge.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Figure 5. Tobago - Recharge Isolines Overlay on GRUs.
Figure 6. Megawatersheds of Tobago
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Figure 7. Alluvial Aquifers of Tobago
Model Calibration Solving the island’s water supply problems required an additional 3-5 million gallons per day of reliable water-into-supply. This would not only reduce the overall deficit, but would increase the reliability of supply. Without the megawatershed paradigm, there would not be an expectation of producing significant additional groundwater on the island. Recharge figures shown in Table 1 imply that if this new model is applicable, then substantial new water is available. In actuality the project executed on the island required the contractor to produce four (4) million gallons of water per day at strategic locations along the island’s water distribution network. Wells drilled within several of the defined megawatersheds produced over a long period of time quantities of water consistent with the predictions of this model. Testing of the wells predicted the capacity of the wells and aquifers (Ingari et al., 2000). Sample constant rate test results are shown in Figure 8. Actual recommended production levels of the individual aquifers are shown on Table 2.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Figure 8. Constant Rate Test Results for Selected Wells.
Table 1. Traditional Aquifers, Megawatersheds and Tested Production at Sites
Megawatershed Model Recharge, MGD
Alluvial Model Recharge, MGD
Tested Production Capacity, MGD
Diamond Estates
1.5
0.0
1.52
Government Farms
0.6
0.24
0.63
Bacolet
1.4
0.19
0.88
Belmont
3.0
0.0
0.68
Bloody Bay
7.7
0.33
0.36
Charlotteville
0.4
0.05
0.16
Aquifer
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment. Table 2. Field Observations at Current Wells
Aquifer
Production
Well Name & No.
MGD
Diamond Estates
June (2001) Water Levels Meters, (MSL)
Critical Water Levels Meters, (MSL)
Diamond Estates #1
0.3
4.38
-16.35
Diamond Estates #2
0.4
3.52
- 0.22
Carnbee #1
0.57
2.54
-35.24
Government Farms
Government Farms #5
0.55
3.11
-63.38
Charlotteville
Charlotteville #2
0.08
-2.80
- 5.64
Mason Hall
Belmont Road #1
0.57
19.6
10.70
Several of the production wells have been pumping into the distribution system for over a year. During that period of time over 575 million gallons have been pumped from the Diamond estates and Government Farms Megawatersheds. Figure 9 shows the water levels in the wells over the dry season and the start of the wet season. From this figure it is apparent that the water levels in all the wells had a steady decline during the dry season and are either leveling out or increasing during the start of the wet season, indicating that active recharge is occurring and validating the megawatershed model. If megawatersheds did not exist then the water levels would have rapidly declined and would have not recovered during the wet season. 0 -5
Drawdown (feet)
-10 -15 -20 -25 -30 -35 -40
Critical Drawdown Diamond Estates = 126 feet Carnbee =191 feet Government Farms = 258 feet
Diamond Estates Carnbee Government Farms
-45 -50 Aug-00
Sep-00
Nov-00
Jan-01
Mar-01
Date
Figure 9. Water Levels in Wells after One Year of Pumping
70
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Jul-01
Sep-01
Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Validation of the estimate of groundwater recharge will take several years of long term monitoring. However, preliminary results based on water level trends and pumping rates seem to indicate the quantity of recharge estimated is within the margin of error. Conclusions and Summary of Comparative Results in Tobago The Tobago megawatershed exploration program has demonstrated that a new paradigm exists with regard to the occurrence of groundwater in crystalline rock terrane. The premise of the megawatershed model is the recognition that fractured crystalline bedrock aquifers contain no primary permeability but do contain pervasive secondary permeability in extensive, three dimensional, fractured bedrock catchment areas which underlie the classically topographically controlled surficial catchments. Megawatersheds are recharged through a network of smaller surface water sub-basins (Groundwater Recharge Units, GRUs) that overlie the intensely fractured crystalline bedrock terrane. These GRUs can be in different surface catchment areas resulting in inter-basin transfer of groundwater through large subsurface fracture networks. Traditional Approach: Groundwater availability using the traditional hydrogeological concepts was computed to be 0.69 MCM/Year. Hydrological calculations of water availability were based on alluvial deposits with recharge areas limited by steep river valleys that rapidly discharge precipitation by overland flow to the surrounding sea. For over thirty (30) years, geological exploration work on the island by several consultants had focused on these alluvial deposits and wells drilled into them have been poor water producers. Well production of the three (3) remaining alluvial wells on the island range from 0.05-0.10 MGD per well. Megawatershed Approach: Calculations of groundwater availability using the megawatersheds hydrogeological concept was computed to be 66 MCM/Year. This 100-fold increase of water supply discovered using the megawatersheds approach over traditional methods is not unusual and is precisely the source of disbelief among hydrologists and geoscientists accustomed to calculating groundwater recharge using traditional watershed models and locating well sites with conventional technologies. Nevertheless, rigorous pumping tests of wells sited and drilled using the megawatersheds exploration programme demonstrated sustainable production capacity exceeding 4.0 MGD, and several wells produced over 0.5 MGD, each without exceeding natural recharge. Several of the bedrock wells producing the near-term Tobago requirement of 2 MGD were placed in service and have been closely monitored by WASA for over twelve (12) months, resulting in confirmation of the predicted safe, sustainable yield of potable fresh water during the worst drought in more than 40 years of record.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
References: Bisson, R.A. (1989) The Megawatersheds Exploration Model. Proceedings of International Conference on Desert Environments, Third World Academy of Sciences, Trieste, Italy. Bisson, R.A., Hoag, R.B., Jr., Ingari, J. and DeMars, R.M. (1990) New Water and Economic Prosperity in the Red Sea Province, Sudan. Technical Feasibility Report and Test and Production Well Plan, BCI Geonetics, Inc. and USAID. Bisson, R.A and El-Baz, F. (1990) The Megawatersheds Exploration Model. In: Proceedings of the 23rd International Symposium on Remote-Sensing of Environment, Environmental Research Institute of Michigan. Burbey, T. J. and Prudic, D.E. (1991) Conceptual Evaluation of Regional Ground-Water Flow in the Carbonate-Rock Province of the Great Basin, Nevada, Utah, and Adjacent States. Regional Aquifer System Analysis. U.S.G.S. Professional Paper, 1409-D. Church, T.M. (1996) An Underground Route for the Water Cycle. Nature, Vol. 380, April. DHV Consultants BV in Association with Delft Hydraulics and Lee Young and Partners (1999) Water Resources Management Strategy for Trinidad and Tobago. Final Report, Annex 1, 1A, 1B, 1C., Government of Trinidad and Tobago, Ministry of Planning and Development. Driscoll, N. and Uchupi, E. (1997) The Importance of Gas and Groundwater Seepage in Landscape and Seascape Evolution, Thalasses, pp. 35-48. Earthwater Technology International, Inc. (2000) Tobago Groundwater Assessment and Well Development Programme Part A – Hydrogeological Assessment. Water and Sewerage Authority of Trinidad and Tobago Technical Report. Enron International, Inc. (1999) Letter to Water & Sewerage Authority of Trinidad and Tobago Presenting Results Of Independent Consultants’ Report Of “Due Diligence” Regarding ETI Team Megawatersheds Groundwater Development Track Record of Success. Falkowska, L. (1998) Anomalies in the Physical and Chemical Structure of the Gdansk Deep Caused by Groundwater Seepage, Oceanologia, No. 40 (2), pp.71-82. Gleick, P.H. (1993) Water in Crisis. A Guide to the World’s Fresh Water Resources. Pacific Institute for Studies in Development, Environment, and Security, Stockholm Environment Institute, Oxford University Press.
Hoag, R.B., Bisson, R.A., Ingari, J.C., Maharaj, U.S., Sankar, R. (2000) The Megawatershed Concept and Recharge Analysis-Sustainable Groundwater Extraction from Bedrock Aquifers
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in Tobago. Proceedings of the Caribbean Water and Wastewater Association 9th Conference, Port of Spain, Trinidad. Huntoon, P.W. (1986) Incredible Tale of Texasgulf Well 7 and Fracture Permeability, Paradox Basin, Utah. Ground Water, Vol. 24, No. 5. Ingari, J. C., Hoag, R.B, Bisson, R.A., Sankar, R. and Jadoo, L. (2000) Exploration and Pumping test results for a High Yield Crystalline Well in Tobago. Proceedings of the Caribbean Water and Wastewater Association 9th Conference, Port of Spain, Trinidad. Magaritz, A. M., Pena, R.H., Suzuki, O. and Grilli, A. (1990) Source of Ground Water in the Deserts of Northern Chile: Evidence of Deep Circulation of Ground Water from the Andes. Ground Water, September-October, Vol. 28, No.4. Maharaj, U.S. (2000) Risk Management in Groundwater Development – The Tobago Example. Proceedings of the Caribbean Water and Wastewater Association 9th Conference, Port of Spain, Trinidad. Mirecki, J.E. and Manheim, F.T. (1998) Fresh Groundwaters on the Southeastern Atlantic Continental Shelf: A Review of Water Quality Data Obtained from Offshore Wells. SECOR Groundwater Symposium, USGS Woods Hole Field Center, Massachusetts, USA. Moore, W.S. (1996) Large Groundwater Inputs to Coastal Waters Revealed by 226RA Enrichments. Nature, Vol. 380. Page, L.R. (1983) Report on Pharaonic Gold Mines and Deposits of Egypt’s Red Sea Province, U.S. Geological Survey. Person, M., Raffensperger, J.P., Ge, S., and Garven, G. (1996) Basin-Scale Hydrogeologic Modeling. Reviews of Geophysics, Vol. 34, February. Simmons, G.M. (1992) Importance of Submarine Groundwater Discharge (SGWD) and Seawater Cycling to Material Flux Across Sediment / Water Interfaces in Marine Environments. Marine Ecology Progress Series, Marine Ecology Program Service, Vol. 84, pp.173-184. Stone, W.J., Leeds, T., Tunney, R., Cusack, G.A., Skidmore,S.A. (1991) Hydrology of the Carlin Trend, NE Nevada, A Preliminary Report. Hydrology Department, Newmont Gold Company. US Department of Energy (1998) Viasbility Assessment of a Repository at Yucca Mountain. Department of Energy/RW-0508, Vol. 1, December. US Geological Survey (1998) Overview of Middle East Water Resources, Water Resources of Palestinian, Jordanian, and Israeli Interest. Compiled by the U.S. Geological Survey for the Executive Action Team, Middle East Water Data Banks Project.
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Megawatersheds Groundwater Assessment and Recharge Calibration on the Island of Tobago, W.I.; A Comparison of Results Using Megawatersheds versus Traditional Methods of Groundwater Assessment.
Authors: Robert A. Bisson Earthwater Technology Trinidad & Tobago LLC Tel: (868) 663-9851 and USA 703-683-8469 Fax: (868) 662-8620 and USA 703-836-4946 E-Mail:
[email protected] Roland B. Hoag and Joseph C. Ingari Earthwater Technology Trinidad & Tobago LLC and HydroSource Associates, Inc. Tel: (868) 663-9851 and USA 603-968-3733 Fax: (868) 662-8620 and USA 603-968-3733 E-Mail :
[email protected] [email protected] Utam S. Maharaj and Learie Jadoo Water and Sewerage Authority of Trinidad & Tobago Tel: (868) 663-7540 Fax: (868) 662-3584 E-Mail :
[email protected]
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad by Laurent de Verteuil1, Alfred W. Stawicki1, Roland B. Hoag1, Robert A. Bisson1, Joseph C. Ingari1, Utam S. Maharaj2 and Kerry Mulchansingh2 Abstract As part of its ongoing program to upgrade and increase national water supplies, the Water and Sewerage Authority of Trinidad and Tobago (WASA), in October 2000, commissioned Earthwater Technology Trinidad & Tobago LLC (ETI) to perform a comprehensive wholeisland Hydrogeological Assessment of Trinidad. This follows upon a similar and highly successful exercise last year by ETI principals in Tobago. The megawatershed concept of groundwater occurrence in fractured bedrock emphasizes the role of structurally mediated hydraulic connectivity across the topographic boundaries of surface watersheds. By integrating detailed fault and fold analysis with aquifer characterization in terms of genetic depositional sequences, this study extends the megawatershed concept to deep sedimentary basins. Data sets used in the evaluation include proprietary analysis of Landsat TM data, radar data from orbital and airborne platforms, aerial photography, geological maps, DEM interpretation and electric and lithologic logs from ca.1000 wells and test boreholes, ca. 3,000 line km of high-resolution 2D multi-channel seismic line data, 100 line km of Controlled Source Audio-frequency Magnetotellurics (CSAMT) resistivity surveys, plus new field geologic mapping and historic geologic reports. Application of the Megawatershed Exploration Program in the Northern and Southern Basins of Trinidad has resulted in the delineation of eighteen sedimentary megawatershed areas and nine aquifer systems. The structural configuration of each megawatershed area determines the gradient and partitioning of groundwater flow. Understanding the depositional setting and genetic evolution of each aquifer system permits predictive modelling of aquifer quality sediment distribution from limited subsurface data. These concepts are illustrated with examples from the 2001 Trinidad Hydrogeological Assessment project. Key words: Geologic complexity; basin structure; sequence stratigraphy; aquifer quality sediments; sedimentary megawatersheds; aquifer characterization Introduction The sustainable use of groundwater resources from sedimentary aquifers requires planned well field development and abstraction, based upon accurate three-dimensional understanding of: (1) aquifer distribution and continuity; (2) internal heterogeneity; and (3) recharge characteristics. Aquifer distribution is determined from the stratigraphic and structural interpretation of outcrop and borehole information, and is represented on geological cross sections and maps. Internal aquifer heterogeneity is evaluated through analyses of aquifer samples and borehole geophysical logs, by comparison with sedimentological data from analogous present-day sedimentary environments and 76
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
depositional systems. Both processes involve an inductive extension from limited information to wider spatial interpretation, based in part on deductive reasoning from established principles. Actual recharge is determined by a complex interaction of subaerial (precipitation, topography, evapo-transpiration, runoff) and subsurface (soil type, rock type, geologic structure) variables. Recharge evaluation quantitatively considers all these variables using computational models that also incorporate qualified assumptions based upon deductive reasoning. The techniques and conceptual framework employed in the interpretation and mapping of aquifer systems are therefore of the utmost economic importance. This is so for both groundwater resource quantification and its subsequent management. In October 2000, the Water and Sewerage Authority of Trinidad and Tobago (WASA), commissioned Earthwater Technology Trinidad & Tobago LLC (ETI) to perform a comprehensive whole-island, “Hydrogeological Assessment of Trinidad, West Indies”. In this paper we showcase the combination of the existing Megawatershed Paradigm with the tenets of genetic sequence stratigraphy, to extend the megawatershed concept to deep sedimentary basins. The value of employing a wide-ranging regional approach to geological mapping in groundwater exploration, using multiple convergent datasets, is a second theme. These concepts are illustrated and discussed using results from the recent Trinidad groundwater evaluation and exploration study. Trinidad Geology Unlike most islands of the Lesser Antilles, Trinidad is of sedimentary origin, rather than volcanic composition. The island lies within a 200 km wide tectonic plate boundary zone, between the Caribbean Plate and the South American Plate (Burke, 1988). This tectonic zone has a predominantly right lateral strike slip character, as the Caribbean Plate pushes to the east, past the South American continent. The area has been tectonically active for the last 30 million years (Oligocene to present) and has a complex geologic history. Trinidad consists of three upthrust ranges of mountains and hills, separated by two deep sedimentary basins (Figure 1). Metamorphic rocks of the Northern Range transition abruptly southwards across the El Pilar – Arima Fault Zone (PAFZ) to undeformed, essentially flatlying, Holocene and Pleistocene alluvial and marginal marine sediments of the Northern Basin. The Northern Basin is a late Miocene – Pleistocene extensional feature with 7000 – 9000 ft of sedimentary fill resting on highly indurated Lower Cretaceous basement. The Guatapajaro – Guico Anticline forms an east-west drainage divide, upon either side of which runoff derived from the south and north, drains into east-west trending transverse river systems along the basin axis (Figure 1). The Northern Basin is open offshore to the east and west and is bound to the south by the northeast trending Central Range (Figure 1). The Central Range of Trinidad is a low topographic feature with prominent limestone ridges. The eastern end of the Central Range consists of indurated Lower Cretaceous wackestones and lower Tertiary sands and shales in a "pop-up" configuration to a restraining bend of a right lateral wench. The formation of the Central Range uplift was a relatively late-stage tectonic event in the evolution of Trinidad, occurring during the uppermost Pleistocene, after the deposition of most of the Northern Basin and Southern Basin sediments. 77
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 1.
Generalized physiographic and structural map of the island of Trinidad, West Indies. PAFZ = El Pilar Arima Fault Zone; CRFS = Central Range Fault System; CTFZ = Central Trinidad Fault Zone; STFZ = South Trinidad Fault Zone.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
In the south-western Northern Basin, Pliocene – Pleistocene sediments of the Talparo Formation are caught up in the younger Central Range deformation and form uptilted sand ridges that are open to surface recharge. These include the important Durham and Sum Sum aquifer systems. South of the Central Range highlands lies the Naparima Fold Belt and the Central Trinidad Fault Zone (CTFZ). The latter is a dominantly right lateral wrench fault system with both transpressional and transtensional components. The Naparima Fold Belt is tectonically active but remains topographically low because of the soft nature of the sediments presently being uplifted. To the south is the Southern Basin, a deep Cretaceous – Tertiary sedimentary basin and prolific hydrocarbon province (Figure 1). The Southern Basin is bounded along the south coast by the South Trinidad Fault Zone (STFZ), an active right lateral wrench system. Bedding along the eastern south coast is vertical and the Southern Range is really a series of low sand-prone ridges, erosionally delineated from upthrust sands and clays (Figure 1). The pervasive compressional deformation between the CTFZ and the STFZ has resulted in uneven hilly terrane with a series of northeast trending thrust anticlines, adjacent to similarly trending, large synclines. The former structures, such as the Rock Dome Anticline (Figure 1), are composed of clay rich, deep marine, lower and middle Tertiary sediments that were deposited in a foreland basin trough. These formations have limited aquifer potential. The synclinal structures, on the other hand, preserve the younger, Neogene shallow deltaic deposits of the proto-Orinoco system. These can be quite sand-prone and in places, therefore, make good aquifers. Data Within the Northern Basin and Southern Basin of Trinidad, an evaluation of aquifer quality sediment distribution was undertaken as part of an island-wide groundwater resource evaluation. Aquifer quality sediments (AQS) are sands and gravels that have sufficient intrinsic permeability to support economic hydraulic conductivity and transmissivity, given adequate recharge. Two seismic surveys provided critical subsurface structural and stratigraphic control for the study. In the Northern Basin a total of 323 line kilometers of 2-D seismic was available. The primary data set was the Northern Basin Consortium (NBC) survey of 1996, which included 15 lines and 282 km (Figure 2). The quality of the NBC survey is excellent. The frequency content within the upper 1.0 sec is dominantly greater than 100 hz. At the relatively slow Pwave velocities (i.e. 6000 ft/s), bed resolution down to 15 ft is possible. The entire data set is oriented NNW-SSE, or approximately parallel to structural dip, with the exception of two perpendicular strike lines. The NNW oriented lines are spaced approximately 2.0 km apart. The Southern Basin seismic data set consists of approximately 2800 km. of 2-D data that was acquired in 1990 and 1991 by Exxon Trinidad Ltd. for the Southern Basin Consortium (SBC). These data include 39 profiles oriented in a grid that measures approximately 2km.x 7km. with the closer spacing being perpendicular to structural strike (Figure 2). The quality of the SBC data is considerably inferior to the NBC seismic for several reasons, both 79
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 2. Surface outlines of the eighteen named sedimentary megawatershed areas delineated in the present study, in relation to the NBC and SBC seismic surveys and the positions of subsurface boreholes, water wells and oil wells that formed part of the analysis. Extensive aerial photomosaics were constructed for much of the Northern Basin and digital elevation model (DEM) and airborne radar (SLAR) lineament analysis was undertaken for the entire island.
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geologic and related to data collection and processing. The frequency content of the SBC data was relatively low (i.e. less than 40hz) and the data was often saturated with noise, especially in the anticlinal areas. The second major subsurface data set available for the study comprised a large number of borehole geophysical logs, primarily Spontaneous Potential (SP) and Resistivity. These were drawn from shallow test boreholes drilled by Dominion Oil in the late fifties and early sixties, from existing water wells, and from a limited number of oil wells (Figure 2). The historical underpinning of borehole location has resulted in some important areas having poor to virtually non-existent well control and others having excellent control. Very little subsurface data are available from the eastern Northern Basin around Sangre Grande, an area that represents a megawatershed discovery of this study. Along the southern flank of the Northern Range, existing water fields and Domoil boreholes result in good coverage (Figure 2). The main axis of the Northern Basin, around the Caroni River drainage system, has relatively few wells, especially towards the west. In the eastern Northern Basin, where there is no seismic and very limited well control, we conducted Controlled Source Audio-frequency Magnetotellurics (CSAMT) Resistivity surveys to successfully image freshwater bearing AQS bodies. CSAMT profiles lack the resolution of seismic methods and cannot resolve genetic stratigraphic surfaces or bedform geometries. The CSAMT technique, however, is cost efficient and very effective for identifying the presence of resistive AQS bodies. In all areas, analysis of surface outcrops and the use of existing surface geological maps provided the primary basis for the integration of subsurface data into a coherent regional basin history model. Sedimentological and facies data from original fieldwork provide the on-the-ground basis for the depositional models extended into the subsurface. Extensive additional geographic and remote sensing data sets, including lineament and geomorphologic landform analysis from digital topography (DEM), orbital and airborne radar (SLAR), aerial photography and proprietary analysis of Landsat ETM data, were all used to supplement and corroborate the basin history and sequence stratigraphic models emerging from the geologic data. All data were compiled in a standardized and integrated surface ArcView™ and subsurface ViewLog™ GIS database. Megawatershed Paradigm The megawatershed paradigm is a concept of the behaviour of groundwater in large subsurface systems, particularly in relation to structurally mediated hydraulic connectivity across the topographic boundaries of surface watersheds (Bisson and El-Baz, 1990). Megawatersheds, in the original sense of the term, are major regional groundwater flow regimes associated with fault and fracture systems induced by predictable tectonic stresses in response to regional plate motions (Bisson and Hofman, 1989). Applied to crystalline Precambrian shield terrains of the major continents, or to volcanic and mafic island arc land masses, such as Tobago, the megawatershed paradigm holds that vast amounts of groundwater are constantly flowing through deep, interconnected networks of fractures and 81
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
dissolution spaces in the subsurface. Such groundwater flows from areas of rainfall and recharge, often in topographic highlands, to distant areas of freshwater discharge, often at the sea floor on the continental shelf. This concept of deep, predictably disposed fracture systems, dynamically maintained in hydraulic connectivity, replaces the still widely held notion of essentially static, deep "fossil" groundwaters filling "dead-end" fracture systems, with most groundwater flow occurring very close to the surface and mainly in sedimentary formations. The genesis of the megawatershed concept is closely tied to advances in quantitative modelling of potential recharge, using proprietary techniques, and based upon extensive use of Landsat TM, airborne radar, and other remote sensing data (Bisson et al., 1986; 1989; Hoag and Everett, 1998). These studies, in places ranging from the continental United States to Somalia and Venezuela, indicated that potential recharge in bedrock terrains is generally two to three orders of magnitude greater than previously imagined when working from conventional assumptions. This result pointed to the existence of previously underappreciated storage capacity and transmissivity, in regional scale, deep fracture systems. Since then, the drilling of numerous high-yield fracture-bedrock wells in New England, Georgia, and most recently in Tobago, has proven and refined the megawatershed concept. In so far as the megawatershed concept leads us to view groundwater systems at an entirely larger scale, and to explore deeper in the Earth's crust, within previously excluded geology, it truly represents a paradigm shift in the discipline of hydrogeology. Sedimentary Megawatersheds The megawatershed paradigm has been previously applied in sedimentary basins, particularly in mixed siliciclastic-carbonate-volcanic successions containing substantial karst terrain. For example, a groundwater study of megawatersheds in peninsula Florida was undertaken in the mid-1980's (Bisson and Hofman, 1989; BCI Inc., unpub.). At the time, based upon inaccurate assumptions regarding recharge and evapotranspiration, most professionals felt that Florida was nearing the limit of groundwater availability. Meanwhile, waste water engineers were relying heavily on poorly documented, highly simplistic models of Florida's aquifers. That work demonstrated the need to accept and map complexity in sedimentary systems in relation to groundwater flow. Until the present study, however, the megawatershed model had not been systematically applied to thick, fine-grained, siliciclastic sequences in deep sedimentary basins. In Trinidad, results of potential recharge analysis for watersheds overlying such basins, indicate that economically vast amounts of water are entering the subsurface system, most of which must eventually be discharged (Hoag et al., 2001; this volume). Such water is primarily stored in sand and gravel aquifers and is transmitted through intergranular pores and fractures. We applied non-conventional correlation techniques, based upon sequence stratigraphic principles, together with structural mapping from seismic profiles, to accurately determine subsurface sand distribution and hydraulic gradient. The integration of our detailed subsurface prospect maps with spatially registered recharge calculations results in the quantitative delineation of a new groundwater resource model that differs fundamentally 82
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 3.
Lithostratigraphic approach to stratigraphic correlation, leading to incorrect "Serpent Tongue" interpretation of bifurcating AQS bodies in the Talparo Formation of Trinidad. (from M.M. Dillon Ltd., 1968). The section is oriented parallel to structural dip (NW) and is approximately 60° off the depositional dip direction (NNE) as determined from outcrop paleocurrent analysis. As presented, the section fails to distinguish (or infers a concurrence) between structural and depositional dip, and interprets an unnatural sand geometry produced by unidentified depositional processes.
from previous aquifer models. Previous models did not adequately address the architectural complexity of aquifer-quality sand distribution (Figure 3). Such newly perceived groundwater systems, comprising a complex interaction of stratigraphic architecture, basin structure, and associated recharge – discharge flow, are herein termed Sedimentary Megawatersheds. Accurate characterization and aquifer modelling of sedimentary megawatersheds requires detailed sequence mapping, using appropriate tools for highresolution imaging of aquifer sands, and genetic sequence stratigraphic correlation techniques. Lithostratigraphy and Traditional Correlation Lithostratigraphy is the classification and mapping of sedimentary strata based upon their physical properties and mineralogy (i.e. their lithology). Notwithstanding the long known principle of the limited lateral continuity of facies (similar lithologic types), lithostratigraphic mapping has historically formed the worldwide basis for the interpretation of sedimentary rocks. At the sub-regional to regional scale, much can be accomplished with this approach; the lithologies of formations and groups reflect depositional environments and broadly track changing basin history. Thus, there is no need to entirely discard the regional lithostratigraphic frameworks built up over many years in countries all over the world. At the field scale needed for detailed aquifer characterization and modelling, however, traditional lithostratigraphic correlation and mapping often leads to an inaccurate interpretation of aquifer distribution and hydraulic connectivity. By uniformly extending correlations between
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
potentially disparate sand occurrences, such interpretations tend to (i) overestimate aquifer continuity and storage capacity, (ii) miscorrelate sands of different ages, and (iii) underestimate architectural complexity and internal heterogeneity (Figure 3). The correlation in Figure 3 is from an actual study and represents a structurally dip-oriented cross-section of the Talparo Formation from the Northern Basin of Trinidad. It was made using the same Dominion Oil Structural Drill Hole (SDH) e-logs that were available for the present study. The correlation in Figure 3 shows a single homogenous sand dipping gently into the subsurface and then bifurcating into an upper and a lower sand, whose combined thickness exceeds that of the updip sand body. This and similar "serpent tongue" crosssections have resulted in the field application of a "Sum Sum Sand" aquifer model that recognizes an Upper and a Lower Sum Sum Sand, plus an updip Undifferentiated Sum Sum Sand, all of which receive recharge from surface soilcrop. While this correlation honours the e-log data, it is geologically implausible. When engineers, hydrologists and other qualified professionals, undertake geological evaluations beyond the realm of their expertise, the products often include overly simplistic aquifer models. Genetic Sequence Stratigraphy Beginning in the 1960's, geologists interested in sand distribution and architecture began quantitatively studying modern depositional systems (beaches, deltas, estuaries, rivers). This approach developed into the discipline of Process Sedimentology (eg. Allen, 1970; Reading, 1978) and its sister discipline, Facies Analysis (Teichert, 1958; Middleton, 1978). The integration of process sedimentology and facies analysis in the context of Walther's Law of the correlation of facies (Middleton, 1973), resulted in the development of new vertical profile facies models for many depositional environments (Walker, 1979). At about the same time sedimentologists were taking a renewed interest in modern depositional environments and developing new facies models, geophysicists in the petroleum industry, working with seismic profiles, began looking not only at faults and basin structure but also at the stratigraphic implications of reflector geometries. This resulted in the development of Seismic Stratigraphy, the precursor to Sequence Stratigraphy (Payton, 1977). Seismic stratigraphers developed a methodology and terminology for analysing and describing seismic geometries that drew upon ongoing research in process sedimentology and vertical facies modelling, as well as Sloss' seminal work on North American intracratonic sequences (Sloss, 1963; Mitchum et al., 1977; Vail, 1987). What all these developments in stratigraphy have in common, is an emphasis on the importance of correctly interpreting generative processes within coeval depositional environments, that are spatially related in genetic depositional systems (Figure 4). Aquifer quality sands and gravels (AQS) must have sufficient intrinsic permeability to support economic hydraulic conductivity and transmissivity. From studies of process sedimentology and facies analysis in modern and ancient environments, it becomes clear that high intrinsic permeability sediments (=AQS) are relatively uncommon, although they may be locally abundant. Bodies of AQS are deposited in a limited number of environments, each having predictable lateral extent and distinct depositional geometries.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 4. Idealized diagram illustrating the basic terminology of genetic sequence stratigraphy and the interpreted temporal relationships and preservational potential of depositional systems tracts (from Weimer and Posamentier1993, after Vail, 1987). The diagram attempts to show that the observed geometry of stratal units (A) is produced by the combined interaction of basin subsidence, sediment supply, and global changes in sealevel (eustasy), acting over geological time (B). Within this basic model, which extends from the coastal plain to the abyssal plain, aquifer quality sediments can be predictively located in specific systems tracts and depositional environments. The sequence stratigraphy paradigm and methodology provides a powerful exploration framework for locating aquifer quality sand and gravel.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
What are needed, therefore, are dynamic models of how depositional systems respond through time to the geological forces of basin subsidence and uplift, global sea-level change and regional sediment supply. Such models form the basis for the stratigraphic paradigm shift of genetic sequence stratigraphy (Haq et al., 1987; Van Wagoner et al., 1988; Figure 4). Methods The delineation of sedimentary megawatersheds as groundwater resources involves the integration of detailed surface and subsurface geological mapping with a hydrological analysis of recharge potential. The assessment of recharge potential for such systems is based upon computative modelling of rainfall, evapotranspiration and runoff, and is treated in the accompanying paper by Hoag et al. (this volume). Actual subsurface pathways and mechanisms for recharge migration in sedimentary basins are usually not possible to map directly and, within the megawatershed concept, represent an area much in need of additional research. Aquifer tests and planned observation well programs provide a key approach for resolving such issues. At the outset of the study, a structural and basin history analysis of the geologic evolution of Trinidad was performed, starting with a review of existing published and unpublished studies (e.g. Kugler, 1953; Suter, 1960; Ablewhite and Higgins, 1968; Barr and Saunders, 1968; Bower, 1968; Saunders and Kennedy, 1968; Pindell and Barrett, 1990; Payne, 1991; Erlich et al. 1993; Babb, 1997; and many others). The geologic map of Trinidad compiled by Dr. Hans Kugler (Kugler, 1961; 1: 50,000 scale) served as the project geological base map. The map was digitized and converted to a UTM projection in GIS ArcViewÔ format, consistent with all other project spatial data, and then modified to incorporate new observations and interpretations from the disparate remote sensing and subsurface data sets. The main AQS systems of the Northern and Southern Basins of Trinidad were broadly known from previous work (e.g. Rohr, 1949; 1955; de Verteuil, 1968). Sedimentologically, however, these units needed to be placed within a sequence stratigraphic framework at the outcrop scale, which could then be extended to the subsurface through e-logs and seismic correlations. Considerable facies analysis of outcrops throughout the island was undertaken to delineate the depositional environments and genetic context of the main AQS systems. The resulting observations and facies models served as "calibration" for the log facies analysis of e-logs in the subsurface. In general, the detail of investigation for any particular area was limited by the amount and quality of the data available from that area. The methods employed in the interpretation of the seismic data from the Northern and Southern Basins were decided upon after a careful examination of the various qualities of seismic data as well as the amount and reliability of other supporting information, such as e-log data that could be used to calibrate the seismic interpretation. This examination led to very different approaches in the type of interpretations that were attempted in the two basins.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad NW
Figure 5.
SE
This dip oriented seismic section across the Ortoire Syncline demonstrates the complexity of the Southern Basin tectonics. Normal and reverse faults have been interpreted along with an apparent unconformable surface which coincides with the contact of the Mayaro Formation. upon the older Moruga Formation.
The data quality in the Southern Basin proved to be problematic. Although abundant surface contacts were available for correlation, the poor seismic data quality made such methods questionable. Although a number of water and oil and gas wells have been drilled in the basin, that control was often clustered, thereby leaving e-log correlations in question. It was therefore determined to limit the initial interpretation of the SBC data to a confirmation of the nature, location and depths of Southern Basin synclines, and to identify the structural styles and fault orientations within the basin (Figure 5). In the western Northern Basin the quality of the NBC seismic data is excellent and supporting e-log data were readily available. It was decided, therefore, to attempt a seismic sequence style of interpretation in this area since it was felt that the data were suitable for the delineation of bedding geometry. The interpretation was begun by first identifying all of the major unconformities that appeared on the sections and correlating these in a ‘loop-tie’ manner (Figure 6). Next all wells that fell within 100m of each of the seismic profiles were identified and were projected into the 2-D line of profile. At the same time, all lithologies and formation tops that appeared on the surface geologic maps were also plotted onto the seismic sections. This would sometimes result in as many as twenty well-ties into a single seismic profile along with three to four surface ties. By correlating and identifying the various formations on the e-logs and from outcrop, it was possible to then place the seismic events into a chronostratigraphic order. As a result of this effort, no fewer than six sequences were identified in the Talparo Formation. Time structure maps at the bases of four of these sequences (Durham, Sum-Sum, Chin-Chin, and Tlp5) were generated and loaded into the Viewlog package for further analysis (Figure 7). Velocity functions were derived from the seismic velocity analyses and used to transform two-way-travel-time to depth below sea-level for each base-of-sequence structure map (Figure 8). From these structure maps, fault systems and fold trends were identified and interpreted through geologic time, resulting in a major refinement of existing tectonic models for the basin and a significant re-ordering in the timing of some key events, such as the uplift and emplacement of the Central Range. Finally, faults that extended to surface on the seismic lines were integrated with the surface geological map, resulting in the naming of at least four new previously undelineated fault systems. 87
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 6A. Partial section of NBC Seismic Line 6. The location of the line is shown in Figures 7&8. (A) Uninterrupted line sub-parallel to structural dip. One second of two-way travel time is shown, representing 3,400 ft of section. Vertical exaggeration is 2.9 resulting in dips appearing steeper than they actually are. The quality of the survey data is evident from the continuity of the reflectors (compare with Figure 5). The shingled relationship of several reflectors from right to left, indicates that general sediment provenance was from the south with transport and progradation towards the north. The noisy data quality between shotpoints 1130 – 1180 results from large surface outcrops of sands of the Sum Sum and Durham sequences, which attenuate the acoustic signal during data collection. Detailed seismic facies, representing the internal stratal relationships of each sequence, are not readily visible at this scale of reproduction.
Such deeply rooted fault systems (e.g. the Couva and Caparo) form the boundaries of some megawatersheds in the basin (Figures 1&2). Next a series of cross-sections for each sequence in each megawatershed area was constructed. Despite the oblique to dip orientation of the NBC survey layout, initial crosssections were made to include wells closest to the seismic lines, which permitted firm wellto-seismic tie-ins. This ensured the validity of the genetic correlations across faults and depositional systems tracts (Figure 9). Infill sections were then created in areas without seismic control and correlated in terms of systems tracts, flooding surfaces, and parasequences. This methodology formed the main basis for delineating sedimentary megawatershed areas, within which AQS systems could be mapped and targeted. Results During this study, eighteen sedimentary megawatershed areas of varying sizes and recharge potential were delineated in the Northern and Southern Basins of Trinidad (Figure 2). Geological structure (faulting and folding) provides the main control on delineating sedimentary megawatershed areas, as this determines the direction of groundwater flow and 88
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
1080
1090
1100 SDH333
1110
1120
1130
1140
1150
1170
1160 SDH499
1180
1190
1200 SDH659
SDH319
1210
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1250 SDH318
RS1
1260
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1290 SDH636
SDH635
1300
SSE
SDH633
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1320
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an Manz
ill a
Figure 6B. Structural and sequence interpretation showing the position of well control and the succession of Talparo Fm. sequences above the Springvale Fm. The main structural feature on this section is the asymmetric folding and associated normal and reverse faulting which converges in a deeply rooted system approximately beneath shotpoint 1230. This structure represents the southeast end of the Caparo Fault System. Note the relative continuity of sequence thicknesses, which indicates that faulting and folding post-dates deposition of the sequences.
subsurface megawatershed divides. Nine genetic aquifer systems are present, each having specific hydrogeologic characteristics such as hydraulic conductivity and internal heterogeneity. Such aquifer characteristics and three dimensional architecture are determined by the sequence stratigraphy and post-depositional diagenetic history of the depositional sequence. Two examples of structurally delineated sedimentary megawatershed areas, and their associated aquifer systems, are next presented in some detail. The Mahaica – Cumuto Syncline and the Caroni – Las Lomas Monocline are two of the seven megawatershed areas that were mapped in the western Northern Basin, west of the Guatapajaro – Guico Anticline (Figures 1,2,7,8). The Durham and Sum Sum sequences provide the aquifer systems for four of these, including the Mahaica – Cumuto Syncline (Durham) and the Caroni – Las Lomas Monocline (Sum Sum and Durham). Structural Delineation The Mahaica – Cumuto Syncline has a surface area of 50 sq. km and is favourably located in a pristine area of high rainfall. It has an elongate crescent shape that curves from northeast towards the north (Figure 7). The southern boundary is formed by vertical reverse faults formed by the emplacement of the Central Range. The northern boundary is formed by the wrench compressional Mahaica Anticline (Figures 7&10). The Mahaica Anticline is a 89
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 7.
Portion of two-way-travel-time structure map of the basal surface of the Durham Sequence in the vicinity of the Mahaica – Cumuto Syncline and Caroni – Las Lomas Monocline megawatershed areas. Contour intervals are 40 milliseconds datumed to sea-level. NBC seismic lines and well control are also shown. The east-west trending Caroni Fault System is in the upper part of the map, forming the northern boundary of the Caroni – Las Lomas Monocline. The faulted area in the bottom left corner is the southeast end of the Caparo Fault System. The map shows the asymmetric synclinal form of the Mahaica – Cumuto Syncline and the related Mahaica Anticline. Structural deformation has resulted in groundwater flow to the northeast in the Mahaica – Cumuto megawatershed and to the west in Caroni – Las Lomas. Such detailed fault and structure mapping is critical to successful well placement and field development.
positive compressional structure that post-dates deposition of the Talparo Formation and disrupts the strata. Within the syncline, however, which is a sag type feature similar to those seen in the Southern Basin, strata are only marginally disrupted and have gentle dips (Figure 10). The southwest boundary is formed by a gentle fold that results in a subsurface groundwater flow divide between this megawatershed area and the Caparo Monocline to the southwest (Figure 7). Along most of the southern margin boundary fault, sands of the Durham Sequence are at surface. These sands dip gently within the syncline and in places come up again on the flanks of the Mahaica Anticline (Figure 10) resulting in excellent recharge potential.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 8.
Portion of structure map of the basal surface of the Sum Sum Sequence converted to depth below sea-level in feet from two-way-travel-time. The contour interval is 100 ft. Structural dip to the northwest is parallel to the main fault trend, an important and positive consideration for hydraulic connectivity to recharge from the main northeast trending sand outcrop belt. Depositional dip is to the north-northeast, suggesting that sand continuity in this tidal system should be good to the west and that, to the southwest, more proximal environments should be encountered within this sequence.
At 196 sq. km., the Caroni – Las Lomas Monocline is the largest of the western Northern Basin megawatershed areas (Figure 2). The Caparo Fault System and the Mahaica Anticline form its southern/southeastern boundary with the Carapichaima Monocline and Mahaica – Cumuto Syncline. The Caparo fault System is approximately 2 km wide and consists of subparallel near vertical normal faults that interconnect at depth in positive flower structures. This structural feature represents a significant subsurface flow barrier and groundwater divide. The northern boundary of the Caroni – Las Lomas Monocline runs due east-west along the structural axis of the Northern Basin, beneath the Caroni River drainage system. These features are associated with Caroni Fault System, a series of vertical, east-west trending strike slip fault segments that have limited vertical displacement and an unquantified amount of dextral lateral displacement (Figures 1&7). Towards the eastern end, the Durham, Caparo, Sum Sum and Chin Chin sequences are at surface. To the west, younger sequences are present. Within the Caroni – Las Lomas Monocline, subsurface groundwater flow is to the northwest along the basin flank and to the west along the basin axis.
91
92 VE = 6.5
SSE
Figure 9. North-South oriented cross section in the Ravine Sable area, datumed at sea-level, of 14 geologic test boreholes and one water well (RS1). Wells are parallel to NBC Line 6; see Figures 6&8. Line of section is approximately between depositional dip (NNE) and structural dip (NW). Asymmetric folding, as shown in Figure 6, provides the main control on AQS depth in the section; offset on faults is typically less than 150 ft. AQS bodies are present in the LST and HST of the Durham and Sum Sum sequences. All the sand bodies eventually thin and pinch out both proximally (updip) and distally (downdip). At the south end of the section, the lowstand sand body in SDH349 thickens to the north in SDH499 and possibly beyond. In other sections, separation and development of LST and HST Durham sands on a scale similar to that exhibited by the Sum Sum in this line, has been observed. In this line, LST Sum Sum sands are at surface in SDH499 and are approximately 200 ft thick in SDH319. About 5 km away, LST Sum Sum Sands have thinned to less than 50 ft. The Caparo and Chin Chin sequences are each 600 – 700 ft thick, and are sand poor in this section. This is typical of the Caparo and Chin Chin in general throughout their know extent in the southern part of the Northern Basin.
NNW
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
SDH536 SDH520 SDH519
NBC Line 9 SDH375
Top Durham
Base Durham
Figure 10. Partial section of NBC Seismic Line 9; see Figure 7 for location. Line illustrates a SSE – NNW section through the Mahaica – Cumuto Syncline and the Mahaica Anticline. SDH375 was used in the preparation of the Talparo Fm. composite log and indicates that most of the Durham sequence in this area is sand prone. These sands outcrop in the southern part of the section and also on the flank of the anticline at SDH520, resulting in a highly prospective aquifer system. Vertical exaggeration is 2.9 and actual dips of the Durham sequence in the line of section are 10° near the southern surface outcrop, declining to 2.5° in the syncline trough. At the deepest part of the syncline the top of the Durham HST sands are at 450 ft below sea-level.
Aquifer Characterization The main aquifer sands in the southern megawatershed areas of the Northern Basin occur in the Durham and Sum Sum sequences. These two sequences that were sequentially depostied under similar environmental and tectonic conditions. Sediment provenance was from the south-southwest (continental South America) and occurred prior to the deformation that caused the uplift of the Central Range. Field and e-log facies analysis, drawn from many outcrop and subsurface sections, resulted in the development of detailed depositional facies and genetic sequence models for the lower four Talparo sequences (Figure 11). Both the Durham and the Sum Sum were deposited rapidly in a gently sloping basin with high sediment influx and low accommodation space, under strong tidal influence. A protoNorthern Range formed a northern barrier to wave action and also enhanced tidal currents. During Pleistocene base-level falls, aquifer quality sands were deposited in lowstand systems tract transgressive tidal bar complexes and in highstand systems tract progradational tidal dunes. During such regional events, the main Orinoco deltaic system, to the east, advanced across the Columbus Basin as far as the continental shelf edge (Wood, 2000). The intervening Caparo and Chin Chin sequences are less sand-prone but in places exhibit baseof-sequence channelization and limited highstand progradational sands. This is consistent with their interpretation herein as downdip genetic equivalents in a “Talparo” sequence model, of the proximal systems tracts represented by the Durham and Sum Sum sequences.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 11. Composite SP and Resistivity log for the Durham, Caparo, Sum Sum and Chin Chin sequences of the Talparo Formation comprising intervals from SDH375 (Durham/Caparo) and SDH325 (Sum Sum/Chin Chin). These log motifs are typical for all four of these sequences throughout their development in the south-western Northern Basin. Note the strong similarity of log facies between the Caparo and the Chin Chin sequences and also between the Durham and the Sum Sum sequences, and the dissimilarity between these two sets. As all four sequences were deposited sequentially in the same tectonic setting over a short interval of geologic time, the two different motifs are interpreted to be from different parts of the general “Talparo” depositional sequence along a dip-oriented profile, the Durham and Sum Sum being more proximal. In this model, proximal parts of Talparo sequences, represented by the Durham and the Sum Sum, preserve a well developed and sand prone Lowstand Systems Trace (LST) and Transgressive Systems Tract (TST) consisting of inter-tidal flats and tidal deltas, while the Highstand Systems Tract (HST) is composed of prograding shoreface tidal dune and bar complexes. More distal parts of sequences, represented here by the Caparo and Chin Chin, have poorly developed LST and TST and a thick HST consisting of five to eight stacked, 50 – 100 ft thick parasequences. These are fine grained but progradational and coarsening upwards, and represent middle neritic muddy shelf environments.
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Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Figure 9 shows the architectural relationship between lowstand and highstand sands of the Durham and Sum Sum sequences. Rapid progradation of the tidal dune fields resulted in relatively homogenous AQS bodies extending several kilometres in the depositional dip direction. The sand itself is clean and well sorted, and is composed mostly of fine, subangular, quartz. No appreciable cementation or other diagenetic processes that could reduce hydraulic conductivity have occurred. The result is an excellent aquifer system having hydraulic conductivities in the range of 8 m/day. Conclusions The megawatershed exploration paradigm applied to deep sedimentary basins is a systematic and integrative methodology based upon the layering of multiple spatial data sets at different scales, in a genetic basin history context. This approach results in the firmly grounded and unambiguous delineation of structurally defined sedimentary megawatershed areas within which groundwater flow is predictable. Surface mapping and sedimentological characterization of depositional sequences, including recognition of lowstand, transgressive and highstand systems tracts and parasequences, permits predictive modelling of subsurface AQS architecture and distribution, even where borehole data are scarce. The recent Trinidad Groundwater Exploration Project experience validates the megawatersheds paradigm of groundwater occurrence for deep sedimentary basins and demonstrates the economic justification for the systematic application of new technology and cutting edge geologic modelling in national groundwater exploration programs. The best strategy for maximising the probability of success in groundwater exploration lies in starting with the widest possible area for investigation, irrespective of apparent precipitation patterns. That is, the limiting factor on groundwater distribution is always the near-surface geology and therefore all facies and their structural relationships need to be fully evaluated. Acknowledgements The authors wish to thank the Water and Sewage Authority of Trinidad and Tobago (WASA), the Petroleum Company of Trinidad and Tobago (Petrotrin) and the Ministry of Energy and Energy Industries (Government of the Republic of Trinindad and Tobago) for permission to publish this paper. S. Balkaransingh, V. Elliot and V. Bally provided technical assistance with data management and preparation of figures. We thank them and all the Earthwater Technology Trinidad and Tobago staff for their support and assistance. We also wish to extend a special expression of appreciation to the technical and support staff at WASA for their ongoing co-operation and enthusiasm for this project. References Ablewhite, K., and Higgins, G. E., 1968, A review of Trinidad, West Indies, oil development and the accumulations at Soldado, Brighton Marine, Grande Ravine, Barrackpore-Penal and Guayaguayare, in Saunders, J. B., ed., Transactions of the Fourth Caribbean Geological Conference, Trinidad 1965: p. 41-73. Allen, J. R. L., 1970, Physical processes of sedimentation: New York, Elsevier, 248 p. 95
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Babb, S., 1997, Tectonics and sedimentation of the Gulf of Paria and Northern Basin, Trinidad [Ph.D. Dissertation]: University of Texas at Austin, 200 p. Barr, K. W., and Saunders, J. B., 1968, An outline of the Geology of Trinidad, in Saunders, J. B., ed., Transactions of the Fourth Caribbean Geological Congress; Port of Spain, Trinidad and Tobago, 28 March - 12 April, 1965: Arima, Trinidad, Caribbean Printers, p. 1-10. Bisson, R. A., and El-Baz, F., 1990, Megawatersheds exploration model, in Proceedings of the Twenty-third International Symposium on Remote Sensing of Environment, Bangkok, Thailand: Ann Arbor, ERIM, p. 247-273. Bisson, R. A., and Hofman, P. D., 1989, Groundwater - the paradoxical economic mineral: Water and Wastewater International, v. 4. Bower, T. H., 1968, Geology of Texaco Forest Reserve Field, Trinidad, W.I, in Saunders, J. B., ed., Transactions of the Fourth Caribbean Geological Conference, Trinidad 1965: p. 75-89. Burke, K., 1988, Tectonic evolution of the Caribbean: Annual Reviews of Earth and Planetary Science, v. 16, p. 201-230. de Verteuil, I., 1968, Trinidad water supply: Proposed works with the estimated costs to meet the Trinidad water supply requirements between 1969 and 1973: Port of Spain, Water and Sewerage Authority, Trinidad and Tobago. Erlich, R. N., Farfan, P. F., and Hallock, P., 1993, Biostratigraphy, depositional environments, and diagenesis of the Tamana Formation, Trinidad: a tectonic marker horizon: Sedimentology, v. 40, p. 743-768. Haq, B. U., Hardenbol, J., and Vail, P. R., 1987, Chronology of fluctuating sea levels since the Triassic (250 million years ago to present): Science, v. 235, p. 1156-1167. Kugler, H. G., 1953, Jurassic to Recent sedimentary environments in Trinidad: Bull. Ass. Susse des Geol. et. Ing du Petrole, v. 20, p. 27-60. ---, 1961, Geological Map of Trinidad: Petroleum Association of Trinidad (1961), scale 1:100,000. Middleton, G. V., 1973, Johannes Walther's Law of the correlation of facies: Geological Society of America Bulletin, v. 84, p. 979-988. ---, 1978, Facies, in Fairbridge, R. W., and Bourgeois, J., eds., Encyclopedia of sedimentology: Stroudsburg, Dowden, Hutchinson and Ross, p. 323-325. Mitchum, R. M., Jr., Vail, P. R., and Thompson, S., III, 1977, Part two: The depositional sequence as a basic unit for stratigraphic analysis, in Payton, C. E., ed., Seismic stratigraphy; applications to hydrocarbon exploration, 26 of Memoir: Tulsa, Oklahoma, American Association of Petroleum Geologists, p. 83-97. 96
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Payne, N., 1991, An evaluation of post-middle Miocene geological sequences, offshore Trinidad, in Gillezeau, K. A., ed., Transactions of the Second Geological Conference of the Geological Society of Trinidad and Tobago: San Juan, Trinidad, Geological Society of Trinidad and Tobago, p. 70-87. Payton, C. E., 1977, Seismic stratigraphy; applications to hydrocarbon exploration: Tulsa, American Association of Petroleum Geologists, 516 p. Pindell, J. L., and Barrett, S. F., 1990, Geological evolution of the Caribbean region: a plate tectonic perspective, in Dengo, G., and Case, J. E., eds., The Caribbean region, H of The geology of North America: Boulder, Geological Society of America, p. 405-432. Reading, H. G., 1978, Sedimentary environments and facies: Oxford, Blackwell, 557 p. Rohr, K., 1949, Geological report on the proposed Siparia water field: Pointe-à-Pierre, Trinidad Leasolds Ltd. Geological Division. ---, 1955, Development of the Sum Sum water sand of Trinidad, B.W.I. Unpublished Report, Trinidad Leaseholds Ltd., Pointe-à-Pierre, Trinidad. Saunders, J. B., and Kennedy, J. E., 1968, Sedimentology of a section in the upper Morne L'Enfer Formation, Guapo Bay, Trinidad, in Saunders, J. B., ed., Transactions of the Fourth Caribbean Geological Conference, Trinidad 1965: p. 121-140. Sloss, L. L., 1963, Sequences in the cratonic interior of North America: Geological Society of America Bulletin, v. 74, p. 93-113. Suter, H. H., 1960, The general and economic geology of Trinidad, B.W.I [2nd, with revised appendix by G.E. Higgins ed.]: London, Her Majesty's Stationary Office. Teichert, C., 1958, Concepts of facies: Bulletin of the American Association of Petroleum Geologists, v. 42, p. 2718-2744. Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A. W., ed., Atlas of seismic stratigraphy, 27 of AAPG Studies in Geology: American Association of Petroleum Geologists, p. 1-10. Van Wagoner, J. C., Posamentier, H. W., Mitchum, R. M., Jr., Vail, P. R., Sarg, J. F., Loutit, T. S., and Hardenbol, J., 1988, An overview of the fundamentals of sequence stratigraphy and key definitions, in Wilgus, C. K., Hastings, B. S., St. C. Kendall, C. G., Posamentier, H. W., Ross, C. A., and Van Wagoner, J. C., eds., Sea-level changes: An integrated approach, No. 42 of Special Publication: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists, p. 39-45. Van Wagoner, J. C., Mitchum, R. M., Jr., Campion, K. M., and Rahmanian, V. D., 1990, Siliciclastic sequence stratigraphy in well logs, cores and outcrops: Concepts for highresolution correlation of time and facies, 7 of AAPG Methods in Exploration Series: Tulsa, American Association of Petroleum Geologists, 52 p. 97
Sedimentary Megawatersheds Delineation: The Role of Genetic Sequence Stratigraphy and Complex Fault Systems Analysis in Groundwater Resource Assessment in Trinidad
Walker, R. G., 1979, Facies Models [1st ed.], 1 of Geoscience Canada Reprint Series: Toronto, Geological Association of Canada. Weimer, P., and Posamentier, H. W., 1993, Recent developments and applications in siliciclastic sequence stratigraphy, in Weimer, P., and Posamentier, H. W., eds., Siliciclastic Sequence Stratigraphy, 58 of AAPG Memoir: American Association of Petroleum Geologists, p. 3-12. Wood, L., 2000, Chronostratigraphy and tectonostratigraphy of the Columbus Basin, eastern offshore Trinidad: Bulletin of the American Association of Petroleum Geologists, v. 84, p. 1905-1928. Authors: Laurent de Verteuil1, Alfred W. Stawicki1, Roland B. Hoag1, Robert A. Bisson1, Joseph C. Ingari1, Utam S. Maharaj2 and Kerry Mulchansingh2 1
Earthwater Technology Trinidad & Tobago LLC 20 Woodlands Road Valsayn North Trinidad, West Indies Tel: (868) 663-8958 or 9851 Fax: (868) 662-8620 email: http://www.caribwater.com 2
Water Resources Agency, Water and Sewage Authority of Trinidad and Tobago Farm Road St. Joseph Trinidad, West Indies Tel: (868) 663-7540 Fax: (868) 662-2810 Corresponding address:
[email protected]
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling by R.B. Hoag, C. Bowman, R. Bisson, Earthwater Technology Trinidad & Tobago P. Restrepo, Optimal Decision Engineering Corporation, R. Sankar, U. Maharaj, Water and Sewerage Authority of Trinidad & Tobago
Abstract The Water and Sewerage Authority of Trinidad and Tobago (WASA) contracted Earthwater Technology Trinidad and Tobago LLC to conduct a Hydrogeological Re-Assessment of the Island of Trinidad. Part of that re-assessment included the development and application of a unique meteorological and GIS/watershed modeling approach to estimate recharge to the Island’s aquifers. Twelve years of precipitation, evapotranspiration, and stream discharge data was acquired from existing meteorological and stream gauging stations. Imagery from geostationary satellites was used in combination with WASA precipitation data to model precipitation and evapotranspiration daily over the twelve-year period using a three layer daily soil moisture accounting model (CROPCASTTM). Results of this model were incorporated in the Precipitation Runoff Modeling System (PRMS), which was calibrated to measured stream discharge. By using daily estimates of precipitation and evapotranspiration, and calibrating to measured streamflow, the model was able to determine daily estimates of groundwater recharge to aquifers underlying the watershed. Unlike traditional methods for determining groundwater recharge which often focus on one parameter (i.e. precipitation, streamflow, etc.) and rely heavily on assumptions of other controlling factors (i.e. infiltration rates, evapotranspiration, changes in soil moisture, etc.), this method allows a rigorous and simultaneous evaluation of multiple data sets. Results of the modeling efforts are illustrated for one watershed in Trinidad. In 1986 and 1989, approximately 93% and 85%, respectively, of recharge occurs in the wet season This multifaceted approach provides the water resource manager the planning tools necessary for the efficient management of aquifers and well fields. The ability to estimate recharge on a temporal and geographic basis can be critical for water resources management and policy. Key Words: Trinidad, groundwater, recharge, GIS, watershed modeling
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Introduction To quantify Trinidad’s groundwater resources, an assessment of groundwater recharge is necessary. Previous studies (M.M. Dillon Ltd., 1967-1970; DeVerteuil, 1968; DHV Consultants BV, 1999) focused primarily on runoff analyses, undocumented assumptions of the amount of rainfall recharging groundwater, safe yields of well fields based on pumping records, and on monthly water balance calculations using only potential evapotranspiration estimates from Piarco Airport. Unlike previous studies, this study employs a unique approach focusing on areal estimates of precipitation and evapotranspiration coupled with rigorous GIS/watershed modelling. To determine groundwater recharge, quantification of the water balance (precipitation, actual evapotranspiration (AET), and stream discharge) over a number of years is essential. For this study, Earth Satellite (EarthSat) Corporation’s CROPCASTTM model provided Island-wide estimates of precipitation and evapotranspiration for a 12-year period. These and other data were then input into the United States Geological Survey’s Precipitation Runoff Modelling System (PRMS), which was subsequently calibrated to measured streamflow. This paper describes the process utilized to estimate groundwater recharge and focuses on one calibrated watershed to illustrate the results. Ultimately, the result of this approach will provide the most accurate estimate of Island-wide groundwater recharge ever accomplished in Trinidad. Setting Trinidad, West Indies, lies in the extreme southeastern Caribbean Sea, 11 kilometers northeast of Venezuela. Trinidad is bordered by the Caribbean Sea to the north, Atlantic Ocean to the east, Columbus Channel to the south, and Gulf of Paria to the west. The Island is approximately 4800 km2 and is characterized primarily by plains and low mountains. Physiographic divisions include the Northern Range, Northern Basin, Central Range, Southern Basin, and Southern Range. Two significant swamps, the Caroni and Nariva, border the western and eastern coasts, respectively (Figure 1). Trinidad’s climate is tropical and characterized by two major seasons: a dry season from January to May and a wet season from June to December. A short dry spell, ‘Petite Careme,’ typically occurs in the middle of the wet season in September or October (Granger, 1982; Water Resources Agency (WRA), 1990). The average annual temperature is approximately 26°C with minor diurnal variations (WRA, 1990). Granger (1982) and the Water Resources Agency (WRA) of Trinidad and Tobago (1990) report an average annual rainfall of approximately 2000 millimeters (mm) with over 78% of the mean annual rainfall occurring during the wet season. Due to the prevailing northeast trade winds and orographic effects, the highland areas of northeast Trinidad receive up to 3800 mm per year of rainfall (Granger, 1982; WRA, 1990). Generally, the amount of precipitation ranges from 1250 mm in the northwest and southwest of the Island to greater than 3000 mm in the northeast (Garstang, 1959). Up to 60% of the total rainfall received in some areas is lost to evapotranspiration (WRA, 1990).
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Figure 1. General location and physiographic map of Trinidad.
Areal Analysis Of Precipitation And Evapotranspiration Using CROPCASTTM CROPCASTTM, developed by Earth Satellite Corporation (EarthSat) Of Rockville, Maryland, was originally designed for real-time crop evaluation and crop production forecasts to meet the needs of European agribusiness. An integral part of accurate crop forecasting is the accurate assessment of precipitation and other meteorological parameters necessary for quantifying a water balance. Real-time satellite coverage from satellites such as Meteosat, GOES, and GMS provide this ability. To increase the accuracy of precipitation estimates, CROPCASTTM integrates rainfall and other meteorological data collected at ground weather stations. In addition to accurately assessing precipitation, CROPCASTTM includes a mathematical evaluation of plant growth related functions. The model database includes local specification of soil type to determine water holding capacity, slope, and preexisting soil moisture to help determine infiltration and runoff. Additionally, the model allows local specification of vegetation type to determine rooting depth, interception, and changes in soil moisture to help estimate potential and actual evapotranspiration. The purpose of this analysis is to provide daily estimates of precipitation and evapotranspiration (potential and actual) on a 4-km grid covering Trinidad for the period 1985 to 1997. To fulfill this goal, precipitation data, other meteorological data, and satellite data were integrated with soils and land cover data in the CROPCASTTM model. Typically, CROPCASTTM requires air temperature, dew point, wind speed, and cloud type and percent cover variations at six-hour intervals. However, limited data were readily available from only two stations in Trinidad: the Piarco Airport and Quare Dam/Hollis Reservoir meteorological stations. Consequently, relationships between variables were developed and spatially extrapolated to determine Island-wide estimates. A description of each data set and the methods utilized to determine daily values for each grid cell are discussed below.
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CROPCASTTM Methodology Precipitation Precipitation data is the most critical component of the CROPCASTTM analysis. To accurately quantify the amount and spatial distribution of precipitation in Trinidad, daily ground precipitation data were acquired from the WRA for the period 1985 to 1997; no data were available for 1994 and the analysis was not conducted for this year. Considerable yearto-year variation in the quality and continuity of the rainfall data was noted. Additionally, the spatial distribution of stations reporting daily rainfall measurements was not as uniform as desired. In several years of the study period, no stations in the southeast of Trinidad reported daily rainfall values. To achieve adequate spatial and temporal continuity, EarthSat utilized meteorological satellite data acquired 3 times daily. At locations with ground station data, the relationship between pixel brightness, which was used as a proxy for cloud density, and precipitation was evaluated. This relationship was then applied to locations with no ground station measurements to determine daily precipitation at other grid cells. Average Air Temperature Average air temperature was determined as the mean of the maximum and minimum temperatures measured at the Piarco Airport meteorological station. To determine the average daily temperature at other grid cells, maximum and minimum temperatures acquired at Piarco were plotted versus time with rainfall to determine the effect of rain on maximum and minimum temperatures. On average, days with rainfall had a maximum temperature one degree less than days with no rainfall; there was no discernable effect on minimum temperature. Thus, for each grid cell on a given day, the temperatures were modified accordingly for those grid cells whose rain mode differed from that at Piarco. Average Relative Humidity Using the same approach to determine average temperature, dew point temperatures were related to precipitation and values (reported four times daily) were modified at the appropriate cells. Relative humidity was then determined from the air temperature and dew point, and averaged for the day. Average Wind Speed Since limited wind speed data were available, EarthSat used a meteorologically justified, subjective method to introduce spatial variation in the data. The airport wind direction was divided into six 60° zones. Each grid cell on the Island was assigned a wind promotion value based on location. If the cell was within two cells of the coastline and the wind direction measured at Piarco had an onshore component, the wind velocity in the cell was promoted by two knots. If the cell included the coastline and the wind direction measured at Piarco had a strong onshore component, the wind velocity in the cell was promoted one additional knot.
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Cells located at higher elevations, but not promoted due to proximity to the coastline, were promoted by two knots. Net Solar Radiation Net solar radiation is a function of the surface albedo, a solar radiation cloud factor, and the sum of direct clear-sky solar radiation at the Earth’s surface and diffuse solar radiation. For each grid cell, surface albedo, ranging from 0.1 for bare ground to 0.25 for dense vegetation, was assigned based on dominant land cover type extracted from a LandSat 7 Thematic Mapper Satellite image. Cloud observations were only available from Piarco and cloud factors were adapted from standard meteorological tables. Several years of data were analyzed to determine the effect of rainfall on solar radiation at Piarco. A linear regression was performed and the relationship was applied to other locations based on rainfall estimates. Direct clear-sky solar radiation and diffuse solar radiation were calculated as a function of the solar constant, the solar zenith angle, an atmospheric transmission coefficient, and time. These calculations were integrated from sunrise to sunset in half-hour time steps at each grid cell. Potential Evapotranspiration Potential evapotranspiration (PET) was calculated using a form of Penman’s equation, which considers air temperature, dew point, wind speed, cloud type and density data, and the albedo of plants. Based on these variables and changing sun angle, PET was calculated every 30 minutes. Actual Evapotranspiration Actual evapotranspiration (AET) was determined using a soil moisture budget model modified after Baier’s and Robertson’s (1966) Versatile Soil Water Budget. This algorithm calculates AET as a function of PET by a series of equations related to plant and soil characteristics. For this analysis, soils data were generalized from the 1:25,000 soils maps of Trinidad compiled by the Land Capability Survey and the University of the West Indies (1973). In particular, the model utilizes the root distribution for each plant growth stage and soil moisture draw down coefficients, i.e. PET is applied to available soil water in each layer of a three-layer model. Water draw down from each layer considers soil properties, rooting distribution, and the actual moisture profile on a given day. Ultimately, the model computes the changes in soil moisture at 24-hour intervals.
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CROPCASTTM Results Precipitation Precipitation varies significantly from year to year in Trinidad (Table 1). During the 12-year study period, the greatest amount of precipitation, approximately 3700 mm, occurred in 1991. The least amount of precipitation, approximately 760 mm, was observed in 1992. Rainfall amounts were most variable in 1997. The 12-year annual average is approximately 2000 mm. In addition to varying with time, precipitation in Trinidad varies spatially (Figure 2). In general, the eastern half of the Island receives more rainfall than the western half. This pattern is a direct result of moisture delivery to the Island via the prevailing northeast trade winds. Maximum amounts of precipitation occur in the northeast of Trinidad where orographic effects also dominate. Minimum amounts of rainfall occur along the west-central coast and in the southwestern tip of the Island. Table 1. Rainfall summary statistics for each year of the study period.
Year
Minimum (mm)
Maximum (mm)
Mean (mm)
Standard Deviation (mm)
1985
1310
3493
2284
563
1986
1113
2975
2065
456
1987
1161
2825
1767
346
1988
1048
3179
2382
471
1989
1000
2325
1735
274
1990
1267
2986
2109
422
1991
964
3694
2083
560
1992
759
2957
1854
497
1993
1226
3289
2166
461
1995
1033
2613
1714
319
1996
1197
3347
2047
474
1997
1073
3621
2290
701
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Figure 2. 12-year annual average precipitation map. Units are in millimeters.
Actual Evapotranspiration Actual evapotranspiration (AET) also varies from year to year (Table 2); however, the amount of variability is significantly less than observed in the rainfall data. Minimal variability is most likely due to minor variations in average daily temperature. On average, annual AET ranges from approximately 590 mm to approximately 1120 mm. The 12-year annual average is approximately 940 mm. Table 2. Actual evapotranspiration summary statistics for each year of the study period. Year
Minimum (mm)
Maximum (mm)
Mean (mm)
Standard Deviation (mm)
1985
657
1124
917
97
1986
686
1183
979
111
1987
558
931
797
63
1988
653
1073
898
97
1989
675
1219
1027
86
1990
690
1186
1020
84
1991
639
1179
1007
114
1992
631
1124
949
100
1993
639
1033
903
80
1995
602
1044
850
80
1996
672
1153
978
93
1997
653
1172
987
114
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Similar to precipitation, AET also varies spatially in Trinidad (Figure 3). In general, more evapotranspiration occurs on the eastern half of the Island. In addition to delivering moisture to the eastern half of the Island, the prevailing northeast trade winds also aid evapotranspiration by actively removing moist air. Furthermore, the eastern half of the Island is less urbanized than the western half. The least amount of evapotranspiration was calculated in the highly developed northwest portion of the Island. A steep gradient in evapotranspiration is also noted between the densely vegetated Northern Range and this section of the Island.
Figure 3. 12-year annual average actual evapotranspiration map. Units are in millimeters.
Aerial Analysis Of Recharge Using The Precipitation Runoff Modeling System (PRMS) The Precipitation-Runoff Modeling System (PRMS) (Leavesley et al., 1983) is a watershed model developed by the United States Geological Survey (USGS) as part of the National Research Program (NRP) Precipitation-Runoff Modeling Project. The PRMS is a deterministic, modular-component model, which determines hydrologic fluxes within a series of reservoirs (Figure 4) for watershed partitions termed Hydrologic Response Units (HRUs).
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Figure 4. Schematic diagram of Precipitation-Runoff Modeling System (PRMS) (modified after Jeton and Smith, 1993 and Leavesley et al., 1983).
For this study, the PRMS was utilized to model groundwater recharge in ten watersheds in Trinidad (Figure 5). Within each watershed, HRUs were delineated and the PRMS was calibrated to measured streamflow data. For each HRU, the water-energy balance was determined and groundwater recharge was calculated. Ultimately, these results will be utilized to quantify Island-wide groundwater recharge. The Hydrologic Response Unit (HRU) Concept Hydrologic Response Units (HRUs) are partitions of watersheds that have a homogeneous hydrologic response to precipitation (Jeton and Smith, 1993). HRUs are characterized by physical properties including topography (elevation, slope, and aspect), vegetation, soils, and geology, and are delineated using the corresponding spatial data sets. Partitioning of a watershed into HRUs allows a water budget calculation for a particular area (i.e. one or a group of HRUs) or the entire basin (Jeton, 1999). Jeton and Smith (1993) offer a comprehensive discussion of methods utilized to delineate Hydrologic Response Units. The following section offers a brief description of HRU delineation in this study.
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Figure 5. Ten watersheds used for calibration of the PRMS. Note that F9-6 is a subwatershed of F9-18.
Identification of HRUs With GIS Data For each watershed, HRUs were identified by integrating various spatial data sets with the USGS’s GIS Weasel. The GIS Weasel is a graphical user interface developed to help modelers in the delineation, characterization, and parameterization of modeling response units (e.g. HRUs) for distributed and lumped parameter models (e.g. the PRMS) (Viger et al., 1998). The various spatial data sets utilized in this process and their relevance to the recharge analysis are discussed below. Digital Elevation Models In determining surface runoff, infiltration, and evapotranspiration, the PRMS utilizes topographic slope and aspect derived from the Digital Elevation Models (DEMs). The incorporation of topographic slope allows the PRMS to determine an area’s contribution to infiltration and surface runoff. By incorporating topographic aspect, the PRMS addresses the effect of varying amounts of solar radiation on evapotranspiration, i.e. evapotranspiration is related to the amount of solar radiation incident on a hillside which is directly dependent on the direction the hillside is facing. Soils Another component essential to the quantification of surface runoff, infiltration, and evapotranspiration is soils data. Soil texture has a direct impact on infiltration, the amount of water storage as soil moisture, and the amount of water available for evapotranspiration. For this analysis, soils were generalized from soils maps of Trinidad (Land Capability Survey and UWI, 1973) to four texture classes: clay, clay loam, sand, and sandy loam. Land Cover
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Land cover data also plays an integral role in quantifying various components of the water balance, particularly evapotranspiration. For this study, EarthSat extracted land cover information from a Landsat 7 Thematic Mapper satellite image acquired on November 24, 1999. For Trinidad, land cover types were generalized to nine classes: forest/evergreen, shrub/scrub, grasslands, barren/sparsely vegetated, urban, agricultural, permanent/herbaceous wetland, mangrove wetland, and water. Geology A geologic interpretation was incorporated into the PRMS via a generalized hydraulic conductivity map. Inclusion of the hydraulic conductivity map allowed the model to account for a subsurface layer and calculate recharge to multiple groundwater reservoirs. Generalized polygons were delineated from the 1:50,000 scale Geological Map Series of Trinidad (Kugler, 1959). Hydraulic conductivities were compiled from existing reports, formation descriptions, and published hydraulic conductivities for consolidated and unconsolidated aquifers (Algar, 1993; DHV Consultants BV, 1999; Driscoll, 1986; and Fetter, 1980). Lineaments, faults, and implied fracture zones were also incorporated in the Northern Range. These areas are assumed to have a higher hydraulic conductivity than the host rock. Results and Discussion To illustrate the results of model calibration and determination of groundwater recharge, this discussion focuses on the Cunapo (F2-1) watershed (Figure 5). The Cunapo watershed, approximately 87 km2, is characterized by low relief with locally occurring hills in the southern portion of the basin. Soils in the watershed are primarily clay; in upper reaches of the catchment, sandy soils are locally dominant. Land cover is primarily forest/evergreen, which includes palm and cocoa trees. The geology of the Cunapo watershed consists primarily of formations rich in clay with minor interbedding of sand. The watershed’s geology is reflected in the hydraulic conductivity distribution, which ranges over orders of magnitude (Figure 6). This geologic setting represents a typical environment found throughout a large portion of the Island. Based on the GIS layers which describe these characteristics, the basin was divided into approximately 130 HRUs (Figure 7). The PRMS was then calibrated to measured streamflow and groundwater recharge was calculated in each HRU. Based on rainfall characteristics, 1986 and 1989 were selected for detailed discussion of model calibration and determination of groundwater recharge in the Cunapo watershed. Typically, average annual precipitation in the catchment is approximately 2450 mm. In 1986 and 1989, average annual precipitation in the basin was approximately 2600 mm and 2000 mm, respectively. Thus, 1986 and 1989 represent wetter-than-average and dryer-thanaverage years. Results of model calibration for the Cunapo watershed are illustrated in Figure 8. In general, modeled streamflow correlates well with measured streamflow although larger errors occur
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
at lower- and higher-than-average flows. These errors may be due to the accuracy of the streamflow data, which depends on the definition and stability of the stage-discharge relationship and on the accuracy and frequency of individual streamflow measurements. DHV Consultants BV (1999) reported that during flood flow events, streamflow gauging station measurements were inaccurate by as much as 50%. Additionally, streamflows that fall outside of the range of the current meter used for rating are also thought to be less accurate. Estimates of groundwater recharge are illustrated in Figures 9 and 10. As expected temporal variations in groundwater recharge are analogous to those in precipitation. In 1986 and 1989, approximately 93% and 85%, respectively, of recharge occurs in the wet season. For both years, total recharge accounts for approximately 2% of the total annual rainfall in the basin. However, even though the watershed received only 30% more rainfall in 1986 than in 1989, 65% more groundwater recharge occurred in the wetter-than-average year. These results validate the need for annual determination of groundwater recharge and daily accounting of the various components of the water balance.
Figure 6. GIS layers describing the Cunapo watershed.
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Figure 7. Cunapo watershed divided into Hydrologic Response Units (HRUs).
Figure 8. Observed and calculated streamflow in the Cunapo watershed for (a) 1986 and (b) 1989.
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
The distribution of groundwater recharge in the watershed for 1986 and 1989 is illustrated in Figure 10. In 1986, groundwater recharge ranges from 50 mm to 70 mm with higher amounts of recharge occurring in the northwest and southeast portions of the basin. In 1989, groundwater recharge varies from 30 mm to 50 mm with higher amounts of recharge occurring in the southwest. A comparison of the spatial distribution of groundwater recharge with the various GIS layers used to delineate the HRUs (Figure 6) does not isolate one parameter dictating the distribution of recharge. This result clearly demonstrates the importance of a GIS based approach in determining groundwater recharge. Unlike traditional methods for determining groundwater recharge which often focus on one parameter (i.e. precipitation, streamflow, etc.) and rely heavily on assumptions of other controlling factors (i.e. infiltration rates, evapotranspiration, changes in soil moisture, etc.), this method allows a rigorous and simultaneous evaluation of multiple data sets.
Figure 9. Estimated groundwater recharge in the Cunapo watershed for (a) 1986 and (b) 1989.
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Figure 10. Distribution of groundwater recharge in the Cunapo watershed for 1986 and 1989. Annual average precipitation is indicated as isohyetals in millimeters.
Conclusions Quantifying the variables necessary to characterize the water balance requires extensive areal coverage of “real time” data. In previous decades, “real time” data with adequate spatial coverage was difficult and costly to obtain. However, with the availability of satellite imagery and widespread use of Geographic Information Systems, a more comprehensive and reliable approach is possible. This study employs this type of approach to estimate groundwater recharge in Trinidad. Due to the temporal and spatial nature of groundwater recharge, a multifaceted analysis approach which considers temporal and spatial variations is necessary to obtain accurate estimates of recharge. Additionally, the high temporal variability of precipitation and streamflow supports the need for model accounting on a daily basis. In addition to providing more accurate estimates by incorporating various data sets and accounting for daily variations, an advantage of this method is the ease of obtaining new and “real time” estimates of groundwater recharge. Once watersheds are parameterized and calibrated, the model can be re-run with new precipitation and evapotranspiration data. Furthermore, the effects of climate change and land use practices on groundwater recharge can be easily evaluated. In addition to providing an accurate assessment of groundwater recharge in Trinidad, results of this study have implications regarding water resources management techniques and policy. Particularly, the temporal variability of groundwater recharge needs to be evaluated for proper management and planning. Since majority of the recharge occurs in the wet season, planners need to determine the safe yield of their well fields on a seasonal basis, particularly if the aquifer storage is not adequate to meet demands throughout the dry season. Additionally, groundwater recharge should be evaluated on an annual basis to account for wetter-than-average and dryer-than-average years. This method also allows for proper
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
management of aquifers that are reaching their safe yield, allowing a closer management of the aquifer and prevention of over-exploitation. Despite the obvious advantages of this approach, an inherent drawback is the reliability on accurate measurements of the various input parameters, particularly meteorological parameters and stream discharge. This approach can be improved by using meteorological data including precipitation, air temperature, wind speed, and humidity with better spatial coverage. Additionally, more accurate measurements of extreme (low and high) flow events in necessary. References Algar, S.T. (1993) Structural, stratigraphic, and thermo-chronological evolution of Trinidad. Ph.D. Thesis, Dartmouth College, Hanover, NH. Baier, W. and G.W. Robertson. (1966) A versatile soil moisture budget. Canadian Journal of Plant Science, Vol. 46, pp. 299-315. De Verteuil, Ian (1968) Trinidad water supply: Proposed works with the estimated costs to meet Trinidad water supply requirements between 1969 and 1973. Appendix IV, p. 33-79, “description and assessment of yields of underground sources of supply”. June 1968. Water and Sewage Authority, Trinidad and Tobago. DHV Consultants BV in association with Delft Hydraulics and Lee Young and Partners. (1999) The Government of Trinidad and Tobago, Ministry of Planning and Development, water resources management strategy for Trinidad and Tobago, final report, annex 1, 1A, 1B, 1C. Driscoll, F.G. (1986) Groundwater and wells 2nd edition. U.S. Filter/Johnson Screens, St. Paul, MN. 1089pp. Fetter, C.W. (1980) Applied hydrogeology. Charles E. Merrill Publishing Co., Columbus, OH. 488pp. Garstang, M. (1959) Tropical island rainfall: a study of the rainfall distribution of Trinidad, West Indies. Woods Hole Oceanographic Institution, Woods Hole, MA. Granger, O.E. (1982) Climatic fluctuations in Trinidad, West Indies and their implications for water resource planning. Caribbean Journal of Science, Vol. 17, pp. 1-4. Jeton, A.E. (1999) Precipitation-runoff simulations for the Lake Tahoe Basin, California and Nevada. United States Geological Survey Water-Resources Investigations Report 99-4110. 61pp.
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Jeton, A.E. and J.L. Smith. (1993) Development of watershed models for two Sierra Nevada Basins using a Geographic Information System. Proceedings of the Symposium on Geographic Information Systems and Water Resources, edited by J.M. Harlin and K.J. Lanfear, American Water Resources Association. Kugler, H.G. (1959) Geological maps of Trinidad. Scale 1:50,000. Petroleum Association of Trinidad. Land Capability and the University of the West Indies (UWI). (1973) Soils maps of Trinidad. Scale 1:50,000 Leavesley, G.H., R.W. Lichty, M.M. Troutman, and L.G. Saindon. (1983) PrecipitationRunoff Modeling System: user’s manual. United States Geological Survey Water-Resources Investigations Report 83-4238. 207pp. M.M. Dillon Ltd. (1967) Trinidad Water Resources Survey, Interim reports numbers. 1 and 2, a co-operative project by the Governments of Trinidad and Tobago and Canada under the Commonwealth Caribbean Assistance Programme. M.M. Dillon Ltd. (1968) Trinidad Water Resources Survey, Interim report no. 3, a cooperative project by the Governments of Trinidad and Tobago and Canada under the Commonwealth Caribbean Assistance Programme. M.M. Dillon Ltd. (1970) Trinidad Water Resources Survey, 5th and final report, a cooperative project by the Governments of Trinidad and Tobago and Canada under the Commonwealth Caribbean Assistance Programme. Viger, R.J., Markstrom, S.L., and Leavesley, G.H. (1998) The GIS Weasel – an interface for the treatment of spatial information used in watershed modeling and water resource management, in Proceedings of the First Federal Interagency Hydrologic Modeling Conference, April 19-23, 1998, Las Vegas, Nevada, Volume II, Chapter 7, pp. 73-80. Water Resources Agency (WRA). (1990) Explanatory notes, hydrogeological maps of Trinidad and Tobago. Water and Sewerage Authority, Republic of Trinidad and Tobago. Authors: Roland B. Hoag,Christine Bowman and Robert A. Bisson Earthwater Technology Trinidad & Tobago LLC and HydroSource Associates, Inc. 20 Woodlands Road, Valsayn North, Trinidad Tel: (868) 663-9851 and USA (603) 968-3733 Fax: (868) 662-8620 and USA (603) 968-3733 E-mail:
[email protected] [email protected]
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Estimation of Groundwater Recharge in Trinidad using Meteorological, Geographic Information Systems (GIS), and Watershed Modeling
Pedro J. Restrepo Optimal Decision Engineering Corporation 1002 Walnut St. Suite 200, Boulder, CO, 80302 Tel: (303) 434-2066 Randolph Sankar and Utam S. Maharaj Water and Sewerage Authority of Trinidad & Tobago Tel: (868) 663-7540 Fax: (868) 662-3584 E-mail:
[email protected]
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands by Scott F. Bender1, Jerome Wallace2, and Richard J. Martin1 1 Shannon & Wilson, Inc., 2Caribbean Utilities Company, Abstract When the Caribbean Utilities Company (CUC) needed to expand their power generation capacity, they explored options for discharge of heated engine coolant water either to the ocean and/or to on-site wells. The CUC provides power to the island’s residents through diesel generators. By its nature, an electric utility like CUC must reject either hot air or warm water. Groundwater is the preferred method used to cool the diesel engines installed in the Cayman Islands in recent years due to its inherent efficiency when compared to the radiator air cooling alternative. Each new 12-megawatt diesel generator and auxiliary would require up to 1,600 gallons per minute of cooling water. The temperature of the spent cooling water (after circulating through heat exchangers) would be up to about 45 degrees Celsius. Shannon & Wilson, Inc. was asked to design an injection well-field that would allow disposal of the clean, but heated water without causing thermal short-circuiting to the wells that supplied the cooling water. Another challenge on the project was to find a way to mitigate the migration of the heated water off site towards adjacent properties and to a nearby desalinization plant. Design of the well-field was complicated by the limited available distance between the supply and disposal well-fields on the plant property, and the island’s geology, which consists of a complex sequence of karst limestone and dolomite. Data from two deep test wells were used to construct the hydrogeologic framework for a groundwater and thermal transport model. Shannon & Wilson, Inc. used MODFLOW to construct the groundwater portion of the model and MT3D, a contaminant transport module to MODFLOW, to simulate thermal transport. Although MT3D is designed to simulate the movement of contaminants, the physical processes describing thermal transport are analogous to those describing contaminant transport. A reinterpretation of the input parameters allowed for the use of MT3D. This approach, using MODFLOW and MT3D, allowed for a level of flexibility during model construction that is not found in many commercially available thermal transport models. Using the model, Shannon & Wilson performed parametric studies to evaluate well-field construction scenarios for various well depth and spacing alternatives. A preliminary abstraction and disposal well-field design was proposed based on these studies. During testing of the two new engines, a 30-day abstraction and disposal test was performed to collect hydraulic and thermal information to incorporate into the groundwater model. The hydraulic and thermal test data were used to derive aquifer coefficients, which were then used to update the existing thermal transport model. After a year of collection of weekly to biweekly water temperature data from a suite of wells at the site, the model was recalibrated and used in a second series of predictive simulations. These analyses were used to evaluate a variety of well-field and operational patterns in case the well-fields were to be expanded in the future. The well-field was successfully operated for a 10 month period. CUC has 117
Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
utilized its ocean disposal option since March 2001 and now has two disposal options as contingency measures. Key Words Power Supply Hydrogeology
Karst Injection
Thermal Transport Aquifer Testing
Introduction The Caribbean Utilities Company (CUC) is located on Grand Cayman Island (Figure 1) and provides power to the island through diesel-fired engines. When the CUC needed to expand their power generation capacity, they explored options for discharge of heated engine coolant water either to the ocean and/or to on-site wells. Groundwater is the preferred method used to cool the diesel engines installed in the Cayman Islands in recent years because of its inherent efficiency when compared with the radiator air cooling alternative. Each new 12megawatt generator requires up to 1,600 gallons per minute of cooling water. The temperature of the spent cooling water (after circulating through heat exchangers) would be up to about 45 degrees Celsius Figure 1. Map of Grand Cayman Island and (°C). Shannon & Wilson, Inc. was asked the CUC Site (Adapted from Ng, 1995) to design an injection well-field that would allow disposal of the clean but heated water without causing thermal short-circuiting to the wells that supplied the cooling water. Another challenge was to minimize the migration of the heated water beyond the site boundaries. Design of the well-field was complicated by the limited available distance to locate the supply and disposal well-fields on the plant property, and the island's geology, which consists of a complex sequence of karst limestone and dolomite. Site Conditions Extensive work on the island’s geology and hydrogeology has been performed by the Water Authority exploratory drilling and by Dr. Brian Jones (1987, 1991, 1994) of the University of Alberta. Fresh water aquifers are relatively rare on the island and none are located in the vicinity of the site. Water supply on the island is typically obtained from relatively shallow aquifers varying between 80 to 200 feet deep. At the domestic water supply well-fields, the salt water is converted to fresh water by reverse osmosis. At these depths, the aquifers are usually brine or salt water quality. This aquifer zone usually coincides with karst features in the underlying dolostone aquifer of the Bluff Formation. It is postulated that the karst
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
(cavity) formations in the Bluff Formation may coincide with the elevation of previous sea levels. Karst zones may occur as deep as 500 feet below present sea level on Grand Cayman. The island aquifers are typically prolific. Most wells on the island are relatively shallow, drilled to the depth where groundwater is encountered. There are few well logs (or geologic descriptions or the rock encountered) prepared by drillers or the well owners. Nearly any amount of water can be obtained by drilling, so in the past there was little incentive to prepare or maintain a hydrogeologic characterization of the island aquifers. We understand that the Water Authority Cayman is currently preparing such a database for a variety of purposes. Understandably, there is very little quantitative information on the hydraulic properties of the aquifers. For design of the well-fields for both abstraction and injection of engine cooling water, hydrogeologic parameters such as hydraulic conductivity, storage, and porosity are required. There are a number of wells on the CUC site that are able to sustain large flow rates, many on the order of 2,000 gallons per minute (gpm) with groundwater level drawdown at the wells of less than 15 feet. Most of these wells are open to the formation at depths of about 80 to 160 feet. Site observations indicate that groundwater levels beneath the site (in both shallow excavations and deep wells) fluctuate nearly simultaneously and with an amplitude similar to tidal changes occurring in coastal waters. This suggests that the aquifer is hydraulically well connected to the ocean and is of a very high transmissivity. The only source of quantitative aquifer data available was through the Water Authority. In conjunction with Dr. Jones, the Water Authority drilled and cored a 500 foot boring at their Lower Valley well-field. Geologic and drilling data were available to us for the core. At that location, cavities were encountered at a depth of about 140 feet, and some large cavities between about 270 and 310 feet. According to Dr. Jones, the sequence of karst formations beneath the CUC site is probably similar to the sequence cored at Lower Valley. The Lower Valley borehole data also included the drilling rates, and other pertinent information. Most useful were the laboratory results of core porosity, hydraulic conductivity, and bulk density. Porosities were very high, generally above 30-percent at depths below 160 feet. In addition, the vertical hydraulic conductivity of the rock was similar to the horizontal hydraulic conductivity. These two points are very significant when considering the ability of the rock to retard the vertical migration of heated water. First, to isolate the supply and injection aquifers, the rock "aquitard" should have a large contrast in hydraulic conductivity of one or two orders of magnitude, in the core, the permeabilities appear to contrast only over a factor of 5. Preliminary parametric groundwater modeling analyses for feasibility design of the wellfields were performed in 1998. At that time disposal of the heated water was anticipated to be deep in the dolostone formations of the island. No deep boreholes had been drilled in the vicinity of the site. Limited deep geologic information was available on the island; the deepest well log was from a borehole drilled at the Water Authority’s well-field located at Lower Valley. This hole was bored to a depth of about 490 feet. No deep wells have been drilled at the power plant site (site wells have been drilled to depths as great as 180 feet).
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
Therefore, an exploratory borehole was drilled to identify rock conditions beneath the site, particularly to identify formations below 200 feet where injection was anticipated. Downhole geophysical tests were then performed in the borehole to provide a better understanding of the rock properties. Drilling activities were initiated in January 1999 in the northwest portion of the CUC property. Drilling was performed by Industrial Services & Equipment, Ltd. (ISE) of Grand Cayman. Air rotary drilling methods were used for this hole. The test hole was drilled to a depth of 370 feet. This hole encountered significant cavity zones between 80 and 120 feet, 173 feet, 220 feet, and 273 feet below ground surface. Each of these cavity zones caused major problems during drilling and completion of the borehole, primarily from the influx of cavity deposits on top of the bit while drilling. A very dense sequence of limestone and dolomite was encountered between depths of about 280 and 330 feet. Underlying this zone was a very soft zone of rock where drill cuttings and core returns indicated rock conditions similar to the marl found at ground surface. The rock conditions were soft enough that the drilling tools could have penetrated the rock without rotation of the bit, therefore they had to be held back during drilling. A number of significant rock features were identified during drilling; these are briefly summarized below: ·
Numerous cavities were encountered during drilling. These were between less than a foot and about 8 feet thick. The cavities are the result of mechanical and solution weathering of the limestone and dolomite underlying the site. Jones (1991) suggested that these zones are horizontally extensive across the island and are the result of prolonged weathering at the shores of ancient seas that had tidal elevations different than present sea level. Many of the cavities contain cavity fill of fresh sediment and shells, dolomitized cavity fill, and cavity deposits of caymanite and other solution in-fillings. Some of the relatively fresh cavity deposits, found principally at depths between 80 and 120 feet, suggest that the cavities are connected vertically as well as horizontally. The degree of vertical connection of deeper cavity zones is unknown. A significant finding is that many of the cavities do not necessarily extend horizontally. Comparison of the depths of the cavities encountered in TH-1 and TH-2 (TH-1 was an adjacent test hole that was abandoned during drilling) shows that they may lie at different elevations even over a horizontal distance of 20 to 30 feet. This is significant in that it suggests that at least the shallow cavity zones are not vertically isolated. The cavities above a depth of about 120 feet were extremely pervious and will accept or transmit very high volumes of water.
·
During drilling, air bubbles formed at ground surface around the rig, though mostly on the south side. Air is used in the drilling process to help lift the drill cuttings out of the hole and to maintain a relatively clean borehole. These bubbles were very evident during drilling and are likely the result of air getting trapped in a cavity, moving horizontally along a cavity, and then rising to ground surface in vertical cracks or along joints in the rock. They therefore indicated that a vertical connection exists between the rock and the ground surface.
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·
An injection well about 170 feet southeast of the drilling location was operating during drilling. The injection water is clean waste water from the plant’s distillers, and is a brine solution with a temperature of about 42°C. The water is injected into the rock at depths between 150 and 200 feet. The warm water was observed during drilling to a depth of at least 130 feet in TH-2 and suggests that the heat is transmitted horizontally, but that vertical connections in the rock also allow the heated water to rise in the rock column.
·
A thick dense portion of limestone and dolomite was encountered between about 290 and 330 feet below ground surface. It was thought that this zone could be used as a barrier to the vertical migration of heated waters, however, the lateral extent of this zone is not known
The above significant findings present a rock profile that contains large cavity systems, particularly shallower than 120 feet, which are capable of transmitting water and heat both horizontally and vertically. Based on the observations of (at least) shallow interconnection of cavities, the design team came to the opinion that the originally conceived model of deep injection and shallow abstraction may not be successful in reducing thermal contamination of the shallow aquifer, and could possibly thermally contaminate the entire aquifer sequence through upward vertical migration through fractures and joint sets. The design team considered a variety of options for disposal of the heated water without causing long-term on- and off-site thermal impacts to the aquifer. The selected alternative consisted of shallow disposal of the thermal water in the karst zone between about 80 and 120 feet and abstraction from the deep zone beneath the relatively dense rock between 290 and 330 feet below ground surface. Under this scenario, the water quality in deeper aquifers should not be significantly altered and the relatively pristine water quality of the lower aquifers would be preserved. It would also eliminate the concern of upward migration of the disposal water and eventual contamination of the upper aquifer. The upper zone is extremely pervious, and, from the nearly perfect tidal efficiency observed in this zone, it appeared to be well connected to the ocean. Therefore, there could be a constant heat sink that could absorb the heat transmitted to the aquifer. This alternative provided a deeper contingency source of water should significant thermal contamination of the on-site wells occur. This design scenario was then incorporated into a groundwater model that incorporated thermal transport. This model is further discussed below. Parametric analyses were performed under a wide array of aquifer parameters to evaluate the potential for on-site thermal short-circuiting between wells and for off-site migration of the heated water. The modeling results indicated that short-circuiting would occur to a limited extent to on-site wells, however, the increase in temperature at these wells was within the design tolerances for cooling the engines that they supplied. No off-site migration of the heated water was predicted within a five year time period. In spring 2000, two sets of abstraction/disposal wells were installed at the site. The well locations and depths were selected based on the results of the preliminary groundwater modeling and standard hydrogeologic design principles. Because of the potential variability in subsurface conditions that could result in short-circuiting between the well-fields, the
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
disposal wells were separated by about 200 lateral feet to minimize well interference. The disposal and abstraction well-fields were separated by about 800 feet across the site with their open intervals in two different aquifers that were separated vertically by over 200 feet. Pumping tests were performed at the well-field so that site specific aquifer parameters could be incorporated into the groundwater model. Groundwater Flow and Heat Transport Model A groundwater flow and heat transport model was constructed to evaluate potential well-field designs and off-site impacts for two sets of new abstraction and disposal wells at the site (Units 35 and 36). Hydraulic and thermal data collected after the new wells were brought on line were used to calibrate the model. The model was used to evaluate the potential for thermal impacts of reinjecting the spent cooling water for various well-field designs. Disposal of the heated water would not be successful if disposal resulted in temperature increases of supply water at existing on-site abstraction wells beyond the site boundaries. A number of computer codes specific to the simulation of heat transport are available. However for this project, MODFLOW was used to simulate groundwater flow, and MT3D was used to simulate heat transport. Although MT3D is a contaminant transport model, the processes governing contaminant transport are analogous to heat transport. A reinterpretation of the input parameters for contaminant transport provided a basis for the use of MT3D to simulate the transport of heat. The form of the equations is similar. If the physical processes governing contaminant transport are equated with the corresponding heat transport processes, then the equation describing contaminant transport can be used for heat transport (Bear, 1972): · · · ·
Advection of contaminants is equivalent to convection of heat. Fickian diffusion is equivalent to Fourier conduction. Dispersion of contaminants is equivalent to dispersion of heat. Sorption to solids is equivalent to relative heat capacity of solid to fluid phases.
MT3D can therefore be used for heat transport, provided temperature variations do not significantly change fluid density, causing free convection. These models were chosen because of their ease of use, the flexibility that comes with MODFLOW, and the wide acceptance of both models. Model Development As previously discussed, a preliminary groundwater flow and heat transport model was constructed based on a hydrogeologic conceptual model. The model was developed from regional geologic reports, verbal descriptions of the wells currently on site, the results of a deep test boring drilled on site, and on observations during installation and testing of Units 35 and 36.
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
There are eight significant hydrostratigraphic layers to a depth of approximately 400 feet below ground surface. The classification of these layers is based on the island stratigraphy, bulk density, porosity, and hydraulic conductivity contrasts. The most significant hydrostratigraphic layer in the sequence is Layer 4, a karst zone 80 to 120 feet below ground surface. This highly karstic layer may be the most productive aquifer on the island and was the proposed aquifer for the new disposal wells. The deepest layer observed at the site, called Layer 8 for this project, is a soft and somewhat karstic dolostone layer. This deep unit was targeted as the aquifer for the new abstraction wells. The layers between Layer 4 and 8 are less permeable and, because of the contrast in hydraulic conductivities, were expected to reduce short-circuiting of the thermal water between the abstraction and disposal wells. Table 1 presents the physical characteristics of the layers coded into the model.
Layer Number 1 2 3 4 5 6 7 8
Stratigraphic Unit Name Marl Ironshore Pedro Castle Upper Karst Dolostone 1 Dolostone 2 Dolostone 3 Dolostone 4
Horizontal Vertical Top Bottom Hydraulic Hydraulic Elevation Elevation Thickness Conductivity Conductivity (ft MSL) (ft MSL) (ft) (ft/day) (ft/day) Porosity 5 -17 22 0.003 0.003 0.10 -17 -31 14 100 20 0.40 -31 -75 44 50 10 0.35 -75 -125 50 1050 525 0.30 -125 -245 120 200 100 0.35 -245 -270 25 100 2 0.30 -270 -325 55 2.4 0.4 0.07 -325 -395 70 300 150 0.20
Specific Storage (1/ft) 2.6E-06 3.0E-06 2.9E-06 2.9E-06 2.9E-06 2.9E-06 2.5E-06 2.7E-06
Table 1. Input Parameters for Groundwater Flow Model
Our approach to groundwater modeling was based on the assumption that flow in the aquifer is similar to that which occurs in a porous media, such as a sand. At this site, the rock sequence appears to be of such high permeability and porosity that on the scale of the model this assumption appears to be valid. This assumption is very important when considering the modeling results in the layers with karst formations. Groundwater flow in karst formations can typically be preferentially in one direction and can be non-Darcian. By assuming that the karst layer responds similarly to porous media, we have averaged the potential flow spatially over the layer. This assumption was confirmed by long-term monitoring of the spread of the thermal plume at existing on-site abstraction wells. Based on the hydrostratigraphy, eight layers were incorporated into the model. The base of the model at –400 feet MSL was conservatively assumed to be a no-flow boundary. Lateral model boundaries extended to the ocean on the south and west. The contact locations of the lower layers with the ocean boundary were determined from bathymetric data surveyed by the Defense Mapping Agency Hydrographic/Topographic Center (1994). To the north and east, surface water boundaries are limited to the first layer because the North Bay (Figure 1) is shallow. North and east boundaries for the lower layers were modeled as constant heads and extend over 10,000 feet from the site to minimize boundary effects from impacting the model predictions. Recharge due to precipitation was assumed to be about 22 inches per year and was input as a uniform rate.
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
Hydraulic inputs to the model are shown in Table 1. Limited information was available regarding the hydraulic properties of each layer. Regional hydrostratigraphy and observations during drilling of test boreholes and abstraction wells provide a basis for estimating hydraulic properties. The hydraulic conductivity of Layer 4 (Upper Karst) and Layer 8 (the abstraction layer) were based on hydraulic testing, observations during wellfield operation, and model calibration. Table 2 presents the input parameters for the heat transport model. Input parameters were based on field measurements of temperature, laboratory measurements of various properties from core samples of several of the layers, and literature values (Bear, 1972 and de Marsily, 1986). The dispersion of heat was modeled with a thermal dispersivity term that was incorporated into the effective conductivity term. The longitudinal and transverse thermal dispersivity terms were assumed to be 4 and 1 feet, respectively (in magnitude), based on calibration values obtained from thermal tracer Effective Thermal Thermal Bulk experiments reported in the Conduction Layer Stratigraphic Density Diffusion literature (de Marsily, 1986). o Number Unit Name (kg/ft^3) (cal/m-sec- C) (ft^2/day) The ocean and the north and 1 Marl 70 0.18 1.72 east perimeters of the model 2 Ironshore 47 0.39 0.93 were assumed to provide a 3 Pedro Castle 51 0.42 1.13 constant temperature boundary 4 Upper Karst 55 0.44 1.40 of 27º C. The ambient 5 Dolostone 1 51 0.42 1.13 temperature of the groundwater 6 Dolostone 2 55 0.44 1.40 was also assumed to be 27º C 7 Dolostone 3 72 0.55 7.29 at the start of the simulations. 8 Dolostone 4 62 0.49 2.33 Table 2. Input Parameters for Heat Transport Model
Sensitivity Analysis Prior to model calibration, a sensitivity analysis was completed for important hydraulic and thermal parameters of the Upper Karst (Layer 4) to evaluate the impacts of varying the values of these parameters on model results. This information provided a basis for determining which parameter(s) to adjust during calibration. The four parameters selected for the sensitivity analysis consisted of hydraulic conductivity, porosity, dispersivity, and thermal conductivity. The values of these parameters were varied over a reasonable range of values based on observed and estimated site conditions: · · · ·
Hydraulic conductivity was raised and lowered by factors of 2 and 10. Porosity was varied between a lower value of 0.1 and a higher value of 0.5. Thermal conductivity was increased over a factor of 2. Dispersivity was increased over a factor of 10.
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
For each sensitivity model run, a 360-day period was simulated with a baseline temperature of 27° C. The resulting temperature profile was observed in Layer 4 at the model cell near the center of the site. The results of the sensitivity analysis indicated that the model was most sensitive to hydraulic conductivity. For the lower range of hydraulic conductivity there was a decrease in temperature of approximately 0.8° and 3° C for the 2x and 10x changes, respectively. For the higher hydraulic conductivity range, the temperature increased by approximately 0.5° and 1.7° C for the factor of 2x and 10x changes, respectively. The sensitivity analyses indicated that the model was not particularly sensitive to variations in porosity, thermal conductivity, or dispersivity. No changes in temperature were calculated as a result of varying these parameters. These results were not unexpected given that thermal transport in the Upper Karst is dominated by thermal convection as a result of the high hydraulic conductivity of this zone. Calibration The results of a pumping test completed at Units 35 and 36 were used to calibrate the hydraulic characteristics in Layer 8 of the model. A hydraulic conductivity of 300 ft/day was initially used to calibrate the model to drawdown observed in the wells during testing. This value caused the model to over-predict drawdown in the layer, however this was considered more conservative for evaluation of well-field spacings. For the Upper Karst zone, production backpressures in the disposal wells were used to calibrate the model. Calibration of the model yielded a hydraulic conductivity of 2,100 ft/day. Baseline temperature data was collected on a weekly to bi-weekly basis from on-site abstraction wells from January 2000 through the startup of Units 35 and 36 in March 2000. Temperature data is still being collected on the same frequency. These data indicated that the groundwater temperature had increased significantly in several of the abstraction wells on the CUC site since the startup of Units 35 and 36. The open interval of these wells is at approximately the same elevation as the Unit 35 and 36 disposal wells. Calibration of the model to observed temperature changes with time provided a better understanding of the overall hydrogeologic system as opposed to the pumping test results, which influenced only a small area. The initial step for calibration of the model to temperature data was to simulate the rate of temperature increase in the abstraction wells with the initiation of the Unit 35 and 36 disposal wells. Calibration of the model to temperature data involved simulating both steady-state hydraulic head and temperature conditions without Units 35 and 36 operating, and then bringing these units on line to observe the changes in temperature in the model at the existing abstraction wells completed in the Upper Karst. This process was completed for each incremental change in hydraulic conductivity until the rate of increase of the modeled temperatures approached those observed on site. Although the initial calibration yielded similar rates of temperature increases, the baseline temperatures predicted by the model were several degrees higher than the observed temperatures. These results indicated that the temperature response in the aquifer was very
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
sensitive to the operational patterns of the disposal wells on site (i.e., the water temperature in the aquifer will rise or drop very quickly in response to disposal well operation). In order to calibrate the model to the observed baseline temperature data and subsequently to the changes in temperature over time, a more accurate representation of actual changes in discharge/abstraction rates and discharge temperatures was needed for the period of interest. The subsequent model incorporated production rates and injection temperatures (where measured) at all wells based on the actual year 2000 actual hours for each of the wells. Additionally, variations in injection water temperature for the disposal wells were incorporated into the model.
Jan-01
Dec-00
Nov-00
Oct-00
Sep-00
Aug-00
Jul-00
Jun-00
May-00
Apr-00
Mar-00
Feb-00
Jan-00
Temperature (degrees Celcius)
The results of model calibration for two sets of pre-buildout abstraction wells completed in the Upper Karst are shown in Figure 2. The model adequately simulated the observed temperature increases in these two wells in addition to four other 36 existing abstraction wells. AW-3 Observed Data Temperature variations in several 34 AW-4 Observed Data AW-3/AW-4 Modeled Data site abstraction wells could not be adequately simulated because of 32 local heterogeneities, gaps in temperature data, and inadequate 30 simulation of the existing well-field operation. However, the model does 28 provide information on aquifer conditions and the movement of heat 26 at these locations. Date
Hydraulic conductivity values used to calibrate the model to the Figure 2. Comparison of Observed Temperature Versus Modeled Temperature for Two Wells in the temperature data tend to over-predict Upper Karst buildup pressures at Unit 35 and 36 disposal wells. Buildup pressures of approximately 5 to 6 feet are simulated by the model as compared to the measured values of 0 and 5 feet at Units 35 and 36, respectively. Simulation of Well-Field Operational Effects Following calibration of the model to the hydraulic and thermal data, the model was used to simulate the operation of the well-field for 2-year and 5-year periods. These simulations can be used to evaluate potential long-term impacts on nearby wells. Two scenarios were evaluated. The first scenario included injection of water at the Unit 35 and 36 disposal wells. The second scenario consisted of injection at only one of these wells (discharge from the other unit was assumed to be routed to the North Sound). A baseline temperature of 27° C was assumed for these scenarios. Figure 3 shows the temperature distribution in Layer 4 (Karst Zone) for the 5-year simulation with both wells on line. Because the Unit 35 and 36 disposal wells were located on the
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
northern edge of the site, and several existing CUC abstraction wells (open to Layer 4) are located south of the new wells, the heated water is captured before moving off site toward the south. The temperature rise in these wells is within the operational thresholds of the existing water-cooled engines.
ABO
The model indicates that temperature increases will occur within each of the layers. Temperature increases on the order of 10° or more C above the abstraction water temperature are predicted to occur within the boundaries of the property for the upper layers (2 to 5) of the model. However, a baseline model scenario without the influence of the Unit 35 and 36 disposal wells was not Unit 35 and 36 completed, and these elevated Disposal Wells temperatures may be partially a result of the preexisting disposal wells. The results indicate that the abstraction aquifer (Layer 8) will experience an approximately 1° to 2° C increase after two years and 2° to 3° C increase after five years. The analyses Unit 35 and 36 Abstraction Wells indicated that 5 years is about the time 24Inc period when the thermal plume reaches a hO utfa ll CUC Site Abstraction Wells near-steady state. There is relatively little difference between the 4-year and 5-year thermal distributions. CORRI
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Disposal/Abstraction Well Location and Designation
32
Thermal Contour Contour Interval = 2 Degrees C
Figure 3. Temperature Contours in Layer 4 for 5-Year Well-Field Simulation
For the second scenario, with only one disposal well discharging to Layer 4, the model predicted a smaller temperature increase in the aquifer as would be expected.
Conclusions A groundwater flow and heat transport model was constructed using MODFLOW and MT3D to evaluate well-field operation at the CUC site on Grand Cayman Island. The model was calibrated to both hydraulic and thermal data. Temperature variations observed over time in several wells were adequately simulated with the model. At locations where temperature variations were not as well simulated, the model provided insight into aquifer behavior. The calibration indicated that the overall hydraulic conductivity of the Upper Karst aquifer was lower than previously estimated, although locally the hydraulic conductivity may be substantially higher or lower. The calibration results also indicated that the temperature of the groundwater is highly sensitive to the operational patterns of the existing well-fields. A more detailed and accurate simulation of the operational patterns may increase the accuracy of the calibration.
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Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
Model simulations indicated that the current operations of CUC wells would not result in a spread of heating water off site within a 5-year period. Elevated temperatures are predicted throughout the subsurface in the vicinity of the CUC site. Slightly elevated temperatures may occur in the deeper abstraction aquifer as a result of the operation of the Unit 35 and 36 wells. The results of this project indicate that simulation of thermal transport can be adequately modeled using the contaminant transport code MT3D if the temperature variations are not significant enough to cause density-dependent flow (free convection). This type of model can provide a relatively accurate tool using readily available software, and can provide an indication of feasibility for groundwater reinjection of spent cooling water. In our opinion, the model predictions presented herein are conservative. The variable subsurface conditions characteristic of karst formations were recognized, and as such, the input parameters were selected such that the model may overpredict the spread heat within the aquifer. Though this potential for off-site impacts appears to be low, CUC has since obtained a license for disposal of the cooling water to the North Sound in their 24-inchdiameter outfall. Through this, they are maximizing disposal to the Sound and minimizing on-site disposal. Acknowledgements We would like to thank the Caribbean Utilities Company for providing the opportunity to work on this project. We would also like to thank Mr. Robert Jackson of Industrial Services and Equipment, LTD. and the Water Authority Cayman for their assistance in providing data and their hydrogeologic observations throughout this project. References Bear, J., 1972. Dynamics of Fluids in Porous Media, Dover Publications, Inc., New York. Defense Mapping Agency Hydrographic/Topographic Center, 1994. Topographic and Bathymetric Map of Grand Cayman Island, United States Government, Bethesda, MD. de Marsily, G., 1986. Quantitative Hydrogeology, Groundwater Hydrology for Engineers, Academic Press, Inc., San Diego. Jones, B., 1994. Geology of the Cayman Islands, in The Cayman Islands: Natural History and Biogeography, Kluwer Academic Publishers, Netherlands, 13-49. Ng, K.C., Jones, B., Beswick, R., 1992. Hydrogeology of Grand Cayman, British West Indies: a karstic dolostone aquifer, Journal of Hydrology, 134 (1992) 273-295. Ng, K.C., Beswick, R.G.B., 1995. Hydrogeochemistry of Grand Cayman, British West Indies: implications for carbonate diagenetic studies, Journal of Hydrology, 164 (1995) 193216. 128
Thermal Injection Well-Field Design, Caribbean Utilities Company, Grand Cayman, Cayman Islands
Authors: 1
Shannon & Wilson, Inc. 400 N 34th St. Suite 100 Seattle, WA, USA E-mail:
[email protected], E-mail:
[email protected] 2
Caribbean Utilities Company, P.O. Box 38 GT, Grand Cayman, Cayman Islands E-mail:
[email protected],
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Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study by Richard N. Stalford, PE, RNS Consulting, and Keith Shirley, PE, CMUD Abstract CMUD wished to use a Geographic Information System (GIS) to track and prioritize each water pipe in the water distribution system for rehabilitation. The criteria for the prioritizing needed to be flexible to be redefined at any point during the analysis and also needed to integrate with the existing Work Order System located on a different server. Criteria were established based on the available data and the influencing factors, which historically have caused issues within CMUD’s water distribution system. A custom application was written to take advantage of the GIS identification system and integrate with two data sources. The prioritization was based on a rating and weighting system that the user could adjust as necessary. This will be a case study of the implementation of the rehabilitation system and grouping of projects. Keywords GIS, Geographic Information System, Water Rehabilitation Systems, Water Systems Introduction Charlotte Mecklenburg Utilities (CMUD) is of the major utilities in North Carolina, which provides quality water service to its customer base. CMUD feeds water to an approximate population of 650,000 people within Mecklenburg County, NC, which is approximately 225 square miles in area. The county is located on the south central border of North Carolina and north central border of South Carolina. The county is very fortunate to have three large lakes constructed by Duke Power on the western edge of the county from which raw water is delivered to three water treatment plant with a Average Day Demand (ADD) of approximately 105 MGD (Million Gallons per Day). The distribution system delivers water to a wide range of land use types from multi-family residential to major industrial parks and facilities. CMUD has an aggressive water quality and distribution maintenance system, which repair and coordinate improvements to a distribution system, which range from ¾-inch to 66-inch in diameter and approximately 3000 miles in total length of potable water lines. The age of the water lines range from the beginning of the 20th century with materials including galvanized, cast iron pipe, asbestos cement, concrete cylinder pipe, copper, ductile iron pipe, steel pipe, polyvinyl chloride, and reinforced concrete pipe. With the ages and material ranges included in the system and as facilities are aging CMUD has found it necessary to take an aggressive approach to pipeline rehabilitation. While funding for such projects is not always an easy sell, one of the most helpful tools in convincing policy makers in funding projects is a cohesive plan to access and address major problem areas. This paper summarizes the approach, programming, and information necessary to make informed and cooperative plans to applying improvement funding to critical areas of the water distribution system.
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Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study
CMUD aggressively examined the available data, what data would be helpful to attain for future decision that may not be available today, and where weak spots in the available data could be improved to make future decision making processes more accurate and streamlined. One of the key elements in creating a full feature system to help make hard decisions in capital rehabilitation improvement is to admit that what data is available is not perfect, not fully populated as desired, may not be totally accurate, and may need a lot of room for improvement. Project Initiation There is no greater need for a project planning than a project so intensively based and founded on historic and infrastructure information. Knowing where the data originated and identifying missing data is as important as knowing the data’s is valid. While the review of data for any project can be intensive, when every decision-making process is based on recorded data it is imperative to have a firm knowledge of the value, reliability, source, and verifiability of the data. CMUD has a rich history of modeling its water distribution system for the basis of an aggressive capital improvement program. In conjunction with the expansion of the system in a city that has an infrastructure that dates back to the end of the 1800’s it is also imperative to manage the repair of an aging infrastructure. It is of little value if the newer infrastructure is functioning at peak performance when the aging infrastructure is failing and falling apart. While the CMUD water distribution system is far from failing to perform, to prevent from getting to that stage CMUD felt that it is imperative to implement as an aggressive rehabilitation/replacement program as part of a newer capital improvement program. CMUD set aside obligated funds in the amount of $10,000,000 to spend over a 10-year period to improve and repair aging infrastructure. The first step in appropriately funding projects was to examine the system in terms of key factors and parameters while clearing indicating sore areas of the water distribution system that need attention. From this examination, an on-going task would result complete projects, which would permit decision to be made in an organized fashion and appropriate to the goals at hand. Project Goals In each case and project it is necessary to determine the main purpose and goal. The main purpose and goal of this rehabilitation/replacement project is very direct and simple. Each pipe should be examined to determine in relation to each other pipe the priority for potential repair. This relative priority set for each pipe is used to create organized projects to rehabilitate an aging system in a systematic fashion ensuring that customer service remain in the highest possible condition with the economic limits of Mecklenburg County’ capability. These priorities should be set in relative order. Historic Data In 1994, CMUD completed the first Water Distribution System Master Plan that specifically incorporated and initiated the first geographical information system (GIS) for the water distribution system. This first installment in the GIS incorporated 12-inch and greater
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Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study
distribution pipelines. In 1998, CMUD increased interest in developing a more comprehensive GIS for the purpose of developing an integrated rehabilitation/replacement program. The GIS was increased from approximately 1,100 pipe elements, for use with the water hydraulic model only, to more than 29,000 pipe elements, which continue to incorporate the hydraulic model but also included a comprehensive GIS model of water elements in the distribution system. This is an appropriate point to clearly define the term “model”. In this case, there are two basic model definitions that could confuse the issues at hand. Engineers refer to models as the hydraulic computational model, which predicts under different water operations and demand systems how a water distribution system will perform. The other definition is associated with the GIS model. The GIS industry, in comparison to the engineering community, defines the GIS itself as graphics with intelligence. For the purpose of this paper, since the engineering issues associated with rehabilitation/replacement of the water distribution system, we will use the engineering definition. While the hydraulic model was not the major issue for this rehabilitation/replacement program, the building of the GIS in conjunction with this project to be able to build a more robust infrastructure for the REHAB system also required continuing to be the graphics basis for the analytical hydraulic model. Over several years, CMUD has been making particular strides in gathering repair work order data to not only organize and determine distribution maintenance performance, but to help in the determination of the aging water system in need of repair. GIS Expansion As already indicated, CMUD embarked on an aggressive program to expand the GIS to include as many pipelines as were included in their records. On such a large system it is very hard to encompass all the data on all the system pipelines. While CMUD has over the years maintained a water atlas system, much of the system was not included within it. Therefore, this again was an incremental approach to attaining a comprehensive water distribution GIS, by incorporating all of the data within the atlas mapping system as the second step in attaining a full system GIS. As stated, this expanded the GIS from approximately 1,100 pipes to just over 29,000. Each of these pipelines is uniquely identified with a pipe number, which is the main identifier through the complete system. Priority Set by Weightings and Ratings The priority for each pipe will be a measure of several factors and the weighting of each. The weight and ratings of each pipeline is based on subjective understanding of the importance of certain physical factors in relation to the available data. The priority of a pipeline is based on the available data in several categories. These categories include: · · · · ·
Pipeline Diameter Pipe Material Pipe Year of Installation Pipe Repair Record Pipeline Location
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· · ·
Municipal Boundaries Central Business District City within a City
Most of these categories are self-explanatory. CMUD has some additional political influences, which were to be incorporated into the computation of the priority for each pipeline. The municipal boundaries are defined as the legal limits of the municipal entities recognized by the State of North Carolina and the state legal system. The other categories, Central Business District and City within a City, are specific local political boundaries that have no physical distribution concerns other than the fact that these pipelines fall within these inherently political areas. It is possible to incorporate factors into a priority computation, which have no physical influence on the performance of the distribution system but never the less have some significance in the bigger picture.
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Table 1 shows the point system associated with the rating for each category used for the CMUD system. This table is an example of the system used, but other categories can be added or subtracted as required. Category Central Business District City within a City Municipality
Main Size
Age (Year of Installation)
Pipe Material
Cemintaous Epoxy Polyethylene Repair Record #/1000' Service Ops Codes: 40A-45Z, 50A-50Z, 55-58, 10A-10U
Rating Yes No Yes No Pineville Charlotte Cornelius Huntersville Matthews Davidson Mint Hill 24"-60" 16"-24" 12"-16" Unknown 6"-10" < 6" <1930 1931-1950 1951-1970 Unknown 1971-1980 1981-1990 1991-2000 CIP AC DIP PCCP RCP Unknown PVC CEM EPX PLY 0/1000' 3/1000' 6/1000' 8>/1000' -
10 0 10 0 10 9 8 6 5 4 1 10 8 6 5 4 2 10 8 6 5 4 2 0 10 9 8 7 6 5 0 0 0 0 0 3 7 10
Table 1 – Ratings for each REHAB Category
Is it necessary to weight each category associated with each pipeline. The total weighting must sum to 100 percent. In Figure 1 the weightings are shown in bullet No. 1. These weightings are again completely controlled by the user and can be changed at any time, but must of course add up to 100 percent. The decision to assign weights to each category was based on the importance of the available data in each category. For example diameter and year of installation were only two of the categories used to assign pipeline priorities but can easily be used to demonstrate the over weighting of categories. Diameter is known for almost 134
Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study
all of the 29,000 plus pipelines but the year of installation was known for only 25 percent of all pipelines in the GIS. Therefore, to maintain integrity of the rating system a weighting system was imposed on top of the ratings. This permits a simple adjustment in weightings as more of the data for the year of installation becomes known. In Figure 1 the data entry screen with the REHAB application permits the user to completely control the weightings, ratings, and the categories to be used for the priority computation. The user has complete control to include new categories, assign new weightings to a category(s), or change the rating system used for a category. Is it important to note that the user has complete control to change these features without the need to ask for reprogramming to the REHAB application. In Figure 1, you will see the coding area, noted by a No. 2 bullet. This area is for the user to code directly the part of the application, which will interpret and compute the rating earned. This code is specifically written in X-based language, something reasonably easy to understand and implement, but versatile enough to provide adequate power. The application HELP gives several examples of this type of coding and steps the user through the process. But from this example you can see that the application is completely under the control of the user and not the programmer. The work order system is a category, which is different from all the others in that it is measured based on the frequency of occurrence rather than the simple fitting into a specific division. For example the diameter is a category that earns a specific number of points depending on a specific size range by number. The WOS repair is based on a frequency of repairs per 1,000 feet. Also the data for the repair can change over time as the number of repair frequency increases. Unless the diameter is recorded as the wrong data, the points earned based on diameter will not change unless the point system changes. Figure 1 – Weighting and Ratings Data Entry Screen from Rehab Application
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Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study
Work Order System CMUD has in place a sophisticated Work Order System (WOS) created by Premier System Designs. This WOS tracks the processing and historic work orders for the water distribution system. Included in the system was a detailed Operations Code for the classification of water system repairs. Over 1,100 Op codes are incorporated into the WOS. While most of these codes are not of interest in prioritizing each individual water pipeline, there were approximately 51 codes of main interest. The WOS system is under the control of the Water Distribution Department, which arranges for and implements repairs for the water and wastewater system. A work order is coded by the operations personnel for the type of repair needed. There are over 1,100 repair codes in the WOS system, but not all of these repairs are related to pipeline replacement or rehabilitation. In , the Ops codes of interest to this program are listed with their general descriptions. In Figure 2, a view of the user’s data entry form is shown. This form is populated from the WOS server where the codes are stored both for the codes of interest for this REHAB application and the total code list for the WOS. By clicking on the Add Code button, the user will get to choose from a complete list of WOS codes for inclusion within the REHAB’s area of concern. Again the user has complete control to include or modify the computation basis for the priorities calculated. It is not necessary for CMUD to require more programming to implement new codes of interest as long as they exist within the WOS. WOS Ops Codes Description Codes Service Repairs Service Renew Various Codes Main Line Repairs
40A - 45Z 50A - 50Z 55-58 10A-10U
Table 2 – WOS Ops Codes used for Rehabilitation/Replacement Program
Figure 2 –Work Order System Operations Repair Codes
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GIS Analysis As indicated, there are several categories, which are basically political or graphically based. This means that a pipeline located within a municipal boundary, or in this case Central Business District effects the priority of the pipeline for rehabilitation. So now the challenge is to determine if a pipeline falls within a geographic boundary. One easy way to accomplish this task is to do what is called intersecting in the GIS. ArcView by ESRI provides several tools to do intersections. By accomplishing this task a table is generated which contain the unique GIS master hook which identifies each pipeline and the geographical identification of either inside a specific boundary or not. In the case of municipal boundaries the names of the districts or municipalities are in the resulting table. In the case of Central Business District, a simple “0” or “1” indicates if a pipeline is inside or outside the boundary. These indicators can be any text or numeric value and are complete open in architecture. The REHAB system ultimately does not care and is not hard codes for one specific indicator or another. In this case, it is completely dependent on the information included in the shape file representing that particular boundary. The shapefile can contain numeric, alphanumeric, or text to indicate one way or another. In Figure 1 the Weighting and Rating view shows a code column on the right side or ratings area. The user controls this code with a generic and open architecture method. For example, municipal boundaries in the shapefile use a field name called “juris” and using text specifically indicates if an area is or is not a particular municipality. Figure 3 shows the coding used for the municipality shape file field name within the REHAB application. The code “alltrim(upper(juris)))=’MINT’” means trim the leading and trailing space from the text, upper means to force the text into upper case which would eliminate any issues if lower case text is used, and juris is the fieldname in the shape file. The user can change any of this free format coding as desired or required should the fieldname in the future change from juris to something else or for that matter a numeric is used instead of text for the municipal names.
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Figure 3 – Weights and Ratings entry screen for Municipalities This is only one example of a geographically based category. The user has the option to add or subtract any category that graphically or non-graphically based. The graphically based information is added to a special project file for ArcView to use in conjunction with the REHAB system and the REHAB help details the importance of updating the information and how to rebuild the APR file should it be necessary. New information becomes available all the time. Municipal, City within a City, or Central Business District boundaries change from year to year. To properly include this information into the computations of the priority it is necessary to ensure that updated information is used. The only constant in the universe is change and not only may the boundaries change but the way the data is organized may change and therefore the user must have the ability to change the base coding used in setting the rates earned as shown in Figure 3. Figure 4 shows the resulting intersection table. At this point all that is necessary is to export the table viewed in Figure 4 to a table on the hard drive of a specific name which is detailed in the REHAB help, then the computational portion of the REHAB system will take over and compute the priorities for each pipeline. The system takes about 20 minutes to compute 29,000 plus priorities. This includes the query to the WOS and all the applicable work orders. Computer Utilizations and Network Requirements The REHAB system is a combination of systems integrated to facilitate the computation of a rehab priority for each pipeline in the system. With the REHAB being the center of the system, other system used are the Work Order System (SQL database), ArcView for intersection of graphical data, Pipeline Shape file of the complete water distribution system, and an ACCESS database to house the non-graphical data as well as the resulting priority of each pipeline. The system is designed to be flexible should any of the peripheral system change with minimal impact or coding requirements. 138
Charlotte Mecklenburg Utilities (CMUD) NC, USA, Water Rehabilitation Integration with Geographic Information System, Case Study
Conclusions The final result of the system is a priority based numeric system applied and computed on request for each pipeline in the water distribution system. The pipelines then are manually grouped into project by need of repair and geographic proximity. This step is necessary to apply appropriate type of repairs into projects and to economically group projects for capital improvement project control. The goals of the project have been met by the REHAB application and its open architecture methodology. Figure 4 shows the resulting computation of the priorities for each pipeline. From this view the user can export the data to any number of simple analysis programs like Microsoft EXCEL to manipulate the data in any fashion necessary to organize the repair into projects.
Figure 4 – Example of ArcView and the Graphic Intersection results with the Priorities shown.
Richard N. Stalford, PE RNS Consulting, Inc. Tel: (704) 821-3842 Fax: (704) 821-3844 E-mail:
[email protected]
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned by Donald E. Lindeman, Tampa Bay Water, and Neil Callahan, R.W. Beck, Inc. Headline -Clearwater, Fla., Feb. 22, 1999 “Proposals from four development teams seeking to build the nation's largest saltwater conversion plant in Tampa Bay have shattered price barriers for desalination plants worldwide. Tampa Bay Water, the regional water utility, said the first-year cost estimates it received for a thousand gallons of desalinated water from a new treatment facility all fell below $2.30-per-thousand-gallons -- with some dipping beneath $2-per-thousand. All the proposals were dramatically lower than finished water costs at other seawater desalination plants under construction elsewhere.” The above statement appeared in a news release after the information contained in the proposals for Tampa Bay Water’s seawater desalination project were presented to the Board of Directors at a public meeting. The water industry is still waiting for the absolute final assessment of the project, which is still not completely available because the plant has just broken ground and has not gotten its final financing. However, the project is still on course to be a landmark project for seawater desalination. Project Background Tampa Bay Water is an interlocal governmental agency established in 1974 as the West Coast Regional Water Supply Authority to develop and supply water while controlling the environmental impacts associated with withdrawals. Tampa Bay Water was reorganized and renamed in 1998, pursuant to an Amended and Restated Interlocal Agreement (“Governance Agreement”) among between its member governments. The Member Governments include Hillsborough, Pasco and Pinellas counties, and the Cities of St. Petersburg, Tampa and New Port Richey. Tampa Bay Water supplies water to the Member Governments, which provide drinking water to approximately 2.0 million people in three counties. Tampa Bay Water’s mission is to provide the Member Governments with adequate and reliable supplies of high-quality water to meet present and future needs in an environmentally and economically sound manner. Tampa Bay Water currently owns and/or manages several public groundwater supply facilities in the three county area. Along with the Governance Agreement, Tampa Bay Water and the Member Governments entered into the “Northern Tampa Bay New Water Supply and Ground Water Withdrawal Reduction Agreement” (“Partnership Agreement”) with the Southwest Florida Water Management District (“SWFWMD”). Pursuant to the Governance Agreement and the Partnership Agreement (the “Agreements”), Tampa Bay Water developed the New Water Plan, a conceptual plan document outlining viable projects consistent with the Tampa Bay Water Master Water Plan that will provide new sources of potable drinking water totaling an annual average permitted production capacity of at least 85 million gallons per day (“mgd”).
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
The Agreements call for the phased reduction of pumping from 11 existing wellfields serving the Member Governments, as new water sources are developed, pursuant to stringent timing requirements. The Agreements specifically require that Tampa Bay Water reduce its average daily withdrawals from the 11 wellfields to the following limits: 158 mgd immediately; 121 mgd by December 31, 2002; and 90 mgd by December 31, 2007. Accordingly, consistent with the New Water Plan and the Agreements, Tampa Bay Water must meet the following specific target deadlines for new water supplies to be permitted, constructed, and in operation: at least an additional 38 mgd by December 31, 2002; and at least another 47 mgd by December 31, 2007. During the past 6 years, Tampa Bay has embarked on a Capital Improvement Program (CIP) for new water supply sources that is one of the largest in the U.S., ranking in the same league with MetWater in Calif, and the MWRA in Mass. The CIP program to add new water supply, treatment and transmission facilities to the existing regional water supply system is valued in excess of $609 million. The CIP covers an area of about 1,000 square miles, and includes 85 miles of pipelines big enough for people to walk through. The CIP’s three major components are: 1) desalination plant; 2) surface water treatment plant, 3) reservoir. These future water production assets are usually referred to as their “crown jewels.” These new supplies are needed to accommodate new population growth, as well as mandated pumping reductions from existing, environmentally stressed wellfields. The Seawater desalination project, in that it is considered a “Drought Proof” source of potable water is an essential component of Tampa Bay Water’s CIP required to treat and deliver the new water supplies to be developed according to the above deadlines. The overall operating strategy for the new regional system will be to baseload seawater desalination facilities, to use as much surface water as available and as can be treated during wet weather, and to rely more on existing and small additional groundwater supplies during dry weather when surface water may not be available. This strategy uses the Floridan Aquifer as a large storage reservoir to be filled during wet weather and withdrawn from during dry weather. This strategy is possible because groundwater use permits have reduced allowable average annual use, but peak rates of pumping and well capacities in the existing wellfields have not been changed Because of the short schedule for project delivery, limited staff availability, and a desire to reduce risks and costs, Tampa Bay Water selected the Design-Build-Own-Operate-Transfer (“DBOOT”) project delivery process for the new 25 mgd capacity seawater desalination treatment plant. By utilizing the DBOOT approach, Tampa Bay Water expected to secure substantial benefits for the Member Governments. These benefits include transfer or allocation of technology risk to the vendor, innovative design, long-term facility operations and maintenance cost efficiencies and guaranties.
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
The proposals titled Best and Final Offer for: Seawater Desalination Water Supply Project” were received on February 17, 1999. The proposal were evaluated based on several factors including plant-siting and design, environmental effects, permittability, product water quality and delivery, and cost factors. The original proposal teams for the seawater desalination project included: n
Florida Seawater Desalination Co. (FSDC), a consortium comprised of U.S. Water LLC, Empower, Inc. and DuPont Permasep Products (E.I duPont de Nemours and Company acting through DuPont Permasep Products)
n
Florida Water Partners (FWP), a consortium comprised of Parsons Infrastructure and Technology Group Inc., a subsidiary of Parsons Corporation and I.D.E. Technologies Ltd., a subsidiary of Israel Chemicals Ltd. Tampa Electric Company has been invited to participate in the consortium
n
PEC/Ionics Partnerships (PEIP), a limited partnership-in-formation comprised of Ionics Tampa Bay (a wholly owned subsidiary of Ionics Inc.) and Progress Desal, Inc. (a wholly owned subsidiary of Progress Energy Corporation)
n
Stone & Webster Water (S&WW), a limited liability company (LLC) to be formed jointly by Stone & Webster Engineering Corporation, Stone & Webster Development Corporation and Poseidon Resources Corporation also including TIC-The Industrial Co., and Tampa Electric Company (TECO).
On December July 19, 1999 Tampa Bay Water signed the Construction and Operation of a Seawater Desalination Plant and Water Purchase Agreement with Stone & Webster Water. Since that time Stone & Webster has been removed from the project due to their bankruptcy and the project company has been renamed Tampa Bay Desal. On December 17, 2000 Tampa Bay Desal signed the turnkey Engineering, Procurement and Construction Contract (the EPC Agreement”) with Ogden Water Systems of Tampa Bay, Inc, the predecessor to Covanta Water Systems of Tampa Bay Inc (“Covanta Water”). In the EPC Agreement Covanta Water agrees to provide the design, engineering, procurement, construction, startup and commissioning of the seawater desalination plant. In January, 2001, Tampa Bay Desal and Covanta Water entered into an Operation, Maintenance, Repair and Replacement Agreement (“the O&M Agreement”).
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Introduction THE FACILITIES Tampa Bay Desal has agreed to construct a reverse osmosis (“RO”) plant, with an installed capacity equal to 28.75 MGD and a guaranteed delivery capacity equal to 25 MGD. TBW has contracted with Tampa Bay Desal for Tampa Bay Desal to engineer, design, construct, outfit, start-up and commission the Project. Tampa Bay Desal in turn has contracted with Covanta Water for Covanta Water to provide design engineering, procurement, outfitting and commissioning services for the Project to allow Tampa Bay Desal to fulfill its obligations to TBW. The Project consists of the seawater inlet structures, pumps and pipelines from both the TECO generating plant condenser outlets and the TECO seawater inlet pump station to the RO plant and the concentrate outfall pipeline from the RO plant back to the TECO condenser outfalls; the RO treatment plant; Product Water storage; pumping system; and Product Water transfer pipeline. The Product Water will be conveyed approximately 14.5 miles to the TBWRWTP site in Brandon, Florida for blending with other new sources of water being developed by TBW. The combined new source water will then be pumped into TBW’s wholesale regional water distribution system for sale to its Member Governments. The RO plant is to be located on an eight and one half-acre site owned by TECO, a local regulated power utility company, adjacent to their Big Bend Power Station in Southwest Hillsborough County. Seawater for desalination will be drawn from the existing cooling water discharge conduits for electric generating units No. 3 and Unit No. 4 at the Big Bend Power Station. The RO concentrate and filter backwash water will be discharged and diluted with discharge cooling water from the power station for transport back to the bay. The pretreatment processes include two-stage upflow filtration with coagulant addition to reduce the raw water silt density index to a range acceptable for reverse osmosis feedwater. The RO system configuration will be a two-pass design, with only the minimum required flow from the first pass being treated by the second pass to produce water that satisfies the water quality and quantity requirements. The first pass RO portion is designed for product recovery of sixty percent. A sixty-percent recovery is at the upper end of recovery for a seawater system. The RO system has been conservatively designed with nominal membrane fluxes of approximately 8 to 10 gallons per square foot per day (“GFD”). The proposed RO system design is based on an operating technique that is not typical but appears feasible and provides economic advantages. With large RO systems, product water can be withdrawn from both ends of each RO pressure vessel. A feature of this mode of operation is that product water withdrawn from the feedwater end of the pressure vessel is of higher quality than product water withdrawn from the reject stream end of the pressure vessel. The RO design proposes to take advantage of this fact, to withdraw and isolate a portion of the lower quality product water from a single RO stage for further processing in a second RO pass. Also included in the project is the construction of a 42-inch diameter water pipeline to move desalinated seawater approximately 14 miles from the RO plant to a storage tank to be 143
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
located at the reception point of Tampa Bay Water at its proposed surface water treatment plant site. The proposed 42-inch pipeline is capable of transporting up to 35 MGD. Tampa Bay Desal will provide two storage tanks that will have a combined capacity of 12.5 million gallons, which equates to 50 percent, or half of the daily flow at 25 MGD. The direct costs of permitting and construction of the Project were originally estimated by the Tampa Bay Desal at $81,853,916. The cost of financing the construction of the facilities was similarly estimated to be $12,581,436 resulting in a total Project cost of $94,435,352.
THE DESIGN BY ENGINEER-
PROCURE-CONSTRUCT (‘EPC”)
Tampa Bay Desal has executed the EPC Contract pursuant to which Covanta Water will design, complete the permitting and construct the Project to be capable of a production capacity equal to 28.75 mgd and a guaranteed delivery capacity equal to 25 mgd subject to minimum seasonal daily flow limitations. Covanta Water has prepared and submitted to Tampa Bay Desal and TBW a conceptual design and a preliminary design submittal for design review. Tampa Bay Desal and Covanta Water are further required, under the WPA, to prepare 50 percent and 90 percent design submittal for review by TBW. The Project consists of five major functional elements: the raw seawater conveyance and concentrate return piping systems; the pretreatment chemical conditioning and filtering processes; the RO membrane treatment; the filter backwash, membrane cleaning waste and flush water treatment processes; and, the Product Water storage, pumping and stabilization processes. A process schematic for the Project is presented in Figure 3-1.
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
Figure 3-1
Tampa Bay Desal Proposed Seawater Desalination Project Desalination Process Schematic
Roughing Filters
Polishing Filters
PRETREATMENT SYSTEM
Tampa Bay
Intake Canal Power Plant 1.4 Billion gallons per day
Discharge Canal
Cartridge Filters
BIG BEND POWER PLANT 44 MGD
Seawater Supply
19 MGD
Filter Backwash Solids
REVERSE OSMOSIS (RO) PROCESS 1st Pass
RO Feed Pump
Lime Stabilization
Chlorination
TAMPA BAY WATER WTP
22.7 MGD 2nd Pass
2.3 MGD
5.0 MGD
7.5 MGD Storage
TO DISTRIBUTION
Water Meter
25 MGD
Energy Recovery Turbine
Concentrate Return
Tampa Bay Desal is obligated by the WPA to perform the work reasonably necessary to characterize the ambient seawater quality sufficiently so as to support the design of the Project. An accurate characterization of the raw water quality is important for two reasons: (1) it provides a firm basis for establishing the process design; and (2) it allows various contractual commitments to be firmly established with an identifiable risk. Consequently, Beck’s review of the conceptual design focused on the raw water characterization, the overall process design including the pretreatment and RO processes, and the raw and Product Water pumping and conveyance systems. The Project is located on an eight and one half-acre Project Site owned by TECO adjacent to the Big Bend Plant in southwest Hillsborough County. TECO operates four power-generating units with once through cooling at the Big Bend Plant. These four cooling condensers operate with three running at 345 mgd and the fourth running at 145
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
359 mgd. The total cooling water flow through the Big Bend Plant and back to the Tampa Bay is approximately 1.4 billion gallons per day. Seawater for the Project will be drawn from the existing cooling water discharge conduits for electric generating units No. 3 and Unit No. 4 at the Big Bend Plant. A common raw water pump station will convey an average design flow rate of 44 mgd of raw seawater from either of the cooling water conduits to the Project. To keep the temperature of the raw seawater at 40°C during periods of high seawater temperature and peak generating, a cooling water intake pump can be used to convey seawater directly from the TECO seawater inlet pump station into the seawater inlet pipeline to control the water’s temperature. The design provides for the addition of gaseous chlorine in the raw water inlet pump station and pipeline as necessary to control the growth of macro and micro organisms and to limit biofouling. The seawater is conveyed by the inlet pumping systems to the inlet of the pretreatment chemical conditioning process. The Project will include four separate parallel lines for the pretreatment of the seawater. The chemical conditioning process is the first step in the pretreatment process of the Project. Filter aids and ferric sulfate are added in the chemical conditioning process to coagulate particulate material for subsequent removal via the filters. The coagulated seawater will then be pretreated using a patented DualSand™ two-stage sand filtration system. The filtered seawater must be pumped via the filtered water feed pumps to the cartridge filters. Chemical feeds for sodium bisulfite and acid are provide at this stage of the pretreatment to provide for dechlorination as needed and pH control. The final element of the pretreatment component of the Project is the cartridge filters. The chemical pretreatment and sand and cartridge filters remove particulate materials from the seawater. The overall objective of the pretreatment processes is to ensure that the quality of the treated seawater is adequate and suitable for the subsequent RO membrane treatment process. The RO process is used to remove dissolved salts and inorganic contaminants from the seawater. RO treatment in simple form means applying a liquid containing water and salts (feed water) under pressure onto a semipermeable membrane. Semipermeable means water can pass through but not some or all the salts. The high pressure drives the water through the RO membrane but most of the salt is retained on the inlet side. The low salt water that passes through the membrane is called the permeate. The high salt concentrate from the feed side of the membrane is the concentrate flow. The amount of permeate flow expressed as a percentage of the feed flow is the recovery rate of the RO membrane for those operating conditions. The RO unit specified for the Project has a recovery rate of 60 percent. This means that for every 100 gallons of feed water applied, 60 gallons of permeate (Product Water) and 40 gallons of concentrate water are produced. The RO membrane has carefully sized pores that are the size of small molecules. The smaller the pore size, the more salts and small molecules that will be retained in the concentrate. Following the pretreatment of the seawater in one of the four filter systems, the treated seawater will be transported to one of seven modular trains which utilize the RO membrane technology. The pretreated seawater from the cartridge filters is conveyed to the High Pressure RO feed pumps. These pumps provide the force necessary for the first pass of the RO treatment. The RO membrane treatment process includes a first pass 146
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
membrane system and a second pass membrane system. The first pass membrane system will include seven modular units equipped with membrane trains with each train rated at 4.17 mgd. A single stage membrane array consisting of 168 pressure vessels with each vessel containing eight membranes was selected by Tampa Bay Desal. The second pass membrane trains will consist of a two stage, concentrate staged array. In the two-pass RO process, an amount of the product flow will be directed to the second pass to meet overall delivered water quality chloride criteria. The treated water from the RO process is called the Product Water. The Product Water from the RO process will be directed to an onsite 5 mgd Product Water storage tank. Three process wastewater streams are produced within the overall RO treatment process. The RO concentrate, the filter backwash wastewater, and the membrane cleaning and rinse water are the wastewater process streams produced during the operation of the Project. Each of these wastewaters must be collected, stored, treated and disposed of properly. There will be two discharge points for the liquid wastes: the local sanitary sewer and the RO plant outfall that flows into the cooling water discharge for the generating units. An average of 18.4 mgd of the combined clarified filter backwash wastewater and the RO concentrate will be diluted and discharged back to the generating plant cooling water discharge for transport back to the Tampa Bay. The RO membrane cleaning and rinse wastewater will be either discharged to the public sewer at the plant or, as permitted to the RO plant outfall. The Product Water from the 5 million gallon on-site storage tank will be pumped via the Product Water Transfer pumps into the Product Water pipeline. Lime and liquid chlorine will be added into the pipeline to increase hardness and stabilize the Product Water for transport to the TBWRWTP site. A 42-inch diameter pipeline will convey Product Water approximately 14.5 miles from the Project to the Point of Interconnection with TBW at the TBWRWTP site. The Product Water will then be conveyed into a 7.5 mgd storage tank to be located at the regional plant site. As proposed, the 42-inch pipeline is to be designed to be capable of transporting up to 35 mgd. The Product Water transfer pumps are to be designed to convey 28.75 mgd. The two storage tanks will have a combined capacity of 12.5 million gallons, which equates to 50 percent, or half of the daily flow of the Project at 25 mgd.
PRETREATMENT The pretreatment processes are one of the key elements of the design of the Project because consistently high quality, pretreated water is needed for the proper operation of the downstream RO system. The two principle objectives of the pretreatment system are: (1) to remove particulate materials from the seawater; and (2) to optimize the pH of the seawater to limit scaling on the downstream RO membranes. Additionally, at the Project, it will be necessary to remove any residual chlorine that may remain in the water from the pre-chlorination for biofouling control. Exposure of the membranes to oxidizing chemicals such as chlorine would cause irreparable harm to the membranes. The pretreatment systems to be used at the Project are as follows: (1) chemical conditioning (addition) with filter aid polymers and with ferric sulfate as a coagulant; (2) two stage sand filtration with DualSand™ filters; (3) sodium bisulfite and acid 147
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
addition for dechlorination and scaling control, respectively; and (4) cartridge filters for polishing. The performance of the RO membrane process relative to its ability to produce adequate quantity and quality of Product Water is contingent on having the effluent from the pretreatment units meet the Pretreatment Effluent Water Quality Requirements contained in the EPC Contract that are presented in Table 3-6 below. Table 3-6 Pretreatment Effluent Water Quality Requirements Parameters Turbidity SDI pH
Concentrations <1.0 <4 6.5
Units NTU SU
These criteria serve as the basis for the RO system design and any performance warranties or guaranties from Hydranautics, the RO membrane designer/supplier. During average conditions approximately 31,600 gpm of the seawater is pumped up to and distributed equally to four trains of DualSand™ two-stage gravity upflow sand filters. A wholly owned subsidiary of CWS is the licensor of the patented DualSand™ filter technology. The technology is being provided to Covanta Water by CWS’s subsidiary. The coagulant ferric sulfate and a filter aid polymer, if needed, will be applied to feed water to the filters. The sand filters are used to clean the seawater by capturing the suspended particulate materials. The sand media acts to strain the solids particles out of the flowstream. The seawater containing the coagulated particulate matter and ferric sulfate will be applied to the bottom of the first stage filters. The first stage filter cells contain approximately seven feet of coarse silica sand as filter media. The effluent from the first stage filters is collected from the filter overflow weirs and then flows by gravity to the bottom of the second stage filters. The second stage filter cells contains approximately five feet of fine silica sand or garnet as filter media. The filtered seawater is collected from the second stage filter overflow weirs and then flows by gravity to the RO backwash tank. The backwash tank is the source of water for the membrane backwash and rinse pump and the cartridge filter feed pumps. The average design hydraulic loading on the filters is 4.7 gpm/ft2 which is within the accepted design range of 3 to 6.5 gpm/ft2. The filters proposed for installation are continuously backwashed upflow sand filters. The captured solids are continuously backwashed out of the filter to clean the filters to avoid blinding. The sand at the bottom of the filter portion of the filter media will be backwashed via an air/water air lift. The design backwash flow rate is reported by Covanta Water to be approximately 3 percent of process flow through the filters. The
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
filter backwash wastewater flows by gravity back to a filter backwash clarifier. The clarified backwash wastewater is conveyed with the RO concentrate and rinse water to an overflow which flows by gravity to the discharge of the TECO condenser for dilution and discharge back to Hillsborough Bay. The settled filter backwash solids from the clarifier will be pumped to a belt filter press for thickening and subsequent disposal as a solid waste. The filtered seawater in the RO backwash tank is to be pumped via the filtered water feed pumps to the cartridge filters. The filtered water will receive in-line chemical conditioning with sodium bisulfite and sulfuric acid. The filtered seawater will be dechlorinated to prevent oxidation of the membranes from the chlorine that may be used to control biofouling. Sodium bisulfite is to be added prior to the cartridge filters. The sodium bisulfite reacts instantaneously with the chlorine prior to neutralize it prior to it being applied to the RO membranes. The dechlorinated effluent from the filters is to be chemically conditioned with sulfuric acid primarily to avoid scaling. Scaling occurs when the concentration of a salt in the concentrate side of the RO membrane exceeds its solubility limit. The salts in question would precipitate and form scale on the membrane. Ultimately the scale would inhibit the performance of the RO process. Scaling is generally due to precipitation from sparingly soluble salts and heavy metal compounds. The addition of sulfuric acid will lower the pH and increase the solubility of the salts to a point where they should not produce scaling. This aids in keeping the salts dissolved. A review of the raw water quality parameters that contribute to scaling with the membrane designer/manufacturer indicated that they had taken reasonable measures to consider scaling control in the design. A pilot study of the two-stage, Dual Sand Filter pretreatment system was conducted by Covanta Water and the results were summarized in February 2001. The pilot study was performed during the period between October and December 2000. This time period encompassed a drought period in this area of Florida. The influent water for the pilot unit was obtained from the condenser discharge stream at the TECO Big Bend Plant. After an initial trial period, the media size and the coagulation process were optimized to produce desired finished water quality. The two-stage pilot filter was capable of reducing influent turbidity from a range of 2 to 5 NTU to a range of 0.035 to 0.048 NTU with corresponding effluent silt density index (“SDI”) values of 2.1 to 3.0. This filter performance is very positive. Covanta has continued to operate the pilot unit to test and optimize various aspects of the design and operation. CONTRACTUAL RELATIONSHIPS THE WPA
The purpose of the project is for Tampa Bay Desal to supply Tampa Bay Water with 25 MGD of desalinated water meeting the water quality specified in the WPA. Tampa Bay Desal is responsible for providing all labor, equipment, materials and supplies, including required renewals and replacements necessary to meet its contractual 149
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
obligations including the permitting, design, construction, operating and maintenance of the Project. In addition, Tampa Bay Desal is responsible for the permitting, ambient conditions, monitoring, financing, design, constructing, owning, insuring, testing, operating and maintaining the Project in accordance with the WPA. The initial term of the WPA is for 30 years from the Completion Deadline Date. The Project will be subject to Acceptance Testing, which is intended to demonstrate that the Project is operational and capable of delivering water for fourteen consecutive days during which any seven days shall be at or above Design Capacity and any seven days shall be at or above 115 percent of Design Capacity. Upon completion of construction of the Project, Tampa Bay Water shall be obligated to accept all Product Water delivered by Tampa Bay Desal up to 115 percent of the Design Capacity. TBW shall pay Tampa Bay Desal the Base Compensation Rate for all Product Water delivered by S&W Water. The rate to be paid for water is based on a relatively complicated monthly formula which includes consideration of fixed charges; power costs; chemical charges; other escalated charges; and assumptions regarding the cost of financing the Project. If the Guaranteed Schedule for construction of the Project is not met for reasons other than due to S&W Water’s cause or Force Majeure, Covanta Water shall pay Tampa Bay Desal liquidated damages for failure to meet the Completion Date in an amount of 20 percent of the Contract Price. Tampa Bay Desal will lease the Project Site from Tampa Electric Company (“TECO”) pursuant to a lease agreement. The term of the lease is for an initial 30 year period and may be extended for up to two consecutive additional periods of 30 years each. Tampa Bay Desal is obligated under the WPA to provide the Product Water in quantities consistent with the Product Water Production System Performance Standards contained in Section 9.1 of the WPA. These standards establish that, except during defined maintenance periods or during a Project expansion pursuant to the WPA, Tampa Bay Desal must meet the following System Production Standards: n
The Project must always produce more than 85 percent of the Design Capacity in any 24-hour period. The Design Capacity is intended to be 25 mgd.
n
The Normal Performance Standard: During the period of the year from June 16 to September 30 and January 1 to March 14, the Project must always produce more than 85 percent of the Design Capacity.
n
The Seasonal Performance Standard: During TBW’s historic period of high water demand from October 1 to December 13 and March 15 to June 15 the Project must always produce more than 95 percent of the Design Capacity.
n
At any time of the year, the Project can produce and TBW will accept, consistent with the other provision of the WPA, up to 115 percent of the Design Capacity.
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
EPC CONTRACT COMMERCIAL TERMS AND CONDITIONS Under the EPC Contract, Tampa Bay Desal has retained Covanta Water to design, engineer, procure, construct and test the Project on a turnkey basis. The general provisions which are required to be contained in the EPC Contract are set forth in the WPA. The EPC Contract requires Covanta Water to design, procure and construct the Project so that it is capable of producing the Design Capacity of 25 MGD of daily average Product Water quality as demonstrated by the acceptance tests to be performed by Covanta Water. The Product Water to be produced by the Project must comply with the standards specified in Exhibit A of the EPC Contract and the WPA. Covanta Water is required to complete construction of the Project by the Substantial Completion Date Guaranteed which date is 548 days after Covanta Water has been given its notice to proceed, provided that such notice is issued no earlier than March 24, 2001. The Substantial Completion Date Guaranteed may be adjusted for certain events, which are specified in the EPC Contract. Covanta Water, as full compensation for its work under the EPC Contract, is to be paid a fixed Contract Price. The Contract Price is subject to escalation based on a formula. The Contract Price is subject to change only upon the issuance of a change order issued by Tamp Bay Desal. Covanta Water is required to achieve the following performance tests for the Project: 1. The certified capacity of the Project is to be at least 25 MGD. For each MGD (or fraction thereof) by which the actual capacity is less than this amount, Covanta Water is to pay Tampa Bay Desal liquidated damages to Tampa Bay Desal. 2. For each kWh by which the actual electric consumption of the project during the acceptance test exceeds the guaranteed electric consumption with respect to the Power Guarantee, Covanta Water is to pay Tampa Bay Desal liquidated damages. 3. In the event that during the acceptance test the actual aggregate cost for chemicals exceeds the Chemical Guarantee, Covanta Water is to pay Tampa Bay Desal liquidated damages equal to the 30 year per value of such cost differential. PERFORMANCE GUARANTEES Under the EPC Contract, Covanta Water is required to provide to Tampa Bay Desal Performance Guarantees with respect to the capacity of the Project, the quality of the Product Water, and the efficiency of the Project as follows: (a) Capacity. The Project must produce Product Water for 14 consecutive days during which any 7 days the output shall be at or above the design capacity of 25 MGD, and any 7 days the output shall be at or above 115% of the design capacity without producing less than the respective specified quantities for any day. 151
Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
(b) Product Water Quality. For the entire 14 day acceptance test period referred to above, the quality of the Product Water must meet the water quality requirements set forth in the EPC Contract. (c) Project Efficiency. The Project must meet guarantees for efficiency both with respect to power utilized and the cost of chemicals. ACCEPTANCE TEST Covanta Water is required to cause the acceptance tests to be performed in accordance with the Acceptance Test Protocols and Procedures set forth in the EPC Contract. The performance procedures include the following minimum guidelines: (1)
Preparation of a log sheet for the Project;
(2)
Determination of the Project power consumption;
(3)
Measurement of the Product Water flow;
(4)
Measurement of the Product Water quality at a storage tank;
(5)
Conducting analytical tests by a certified lab to demonstrate that the Product Water quality standards are met;
(6)
Measurement of chemical consumption;
(7)
Concentrate discharge must be in compliance with permit limits.
THE O&M AGREEMENT Under the O&M Agreement, Tampa Bay Desal has retained Covanta Water to operate, maintain, and to make equipment repairs and replacements to the project to generally fulfill the operational obligations of Tampa Bay Desal under the WPA. The O&M Agreement requires Covanta Water to operate, maintain, make equipment repairs and replacements without limitation to the Project to be assured of the continued operation consistent with the established Plant Capacity; Prudent Industry Practices; all applicable Legal Requirements; and, the terms of the O&M Agreement. The Product Water to be produced by Covanta Water must comply with the standards specified in the O&M Agreement. Pursuant to the provisions of the WPA, following the in-service date of the Facilities, the amount of money Tampa Bay Water will pay Tampa Bay Desal for each thousand gallons of delivered Product Water will be determined by the Base Compensation Rate and either the Excess Production Compensation Rate or the Standby Compensation Rate should the Facility be placed on Standby, and other amounts associated with the cost of additional compliance monitoring, abnormal influent and reduction notices as described below. Tampa Bay Water will pay Tampa Bay Desal for the Product Water it does not accept up to the design capacity of 25 MGD in accordance with the Standby Compensation Rate of the WPA. As set forth in the WPA in the initial year, assuming Tampa Bay Water receives and accepts 25 MGD or 9,125,000,000 gallons of Product Water annually, it is estimated that they will pay Tampa Bay Desal approximately
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
$15,622,000. There are many assumptions inherent in this estimate that have yet to be finalized such as the final cost of capital and electric rates. Further, there are a number of adjustment factors in the fee formula such as for raw water salinity and temperature that can have an effect on the actual fees paid. Dollars Per 1000 Gallons of Delivered Water (1) $0.894
[2]
Power Cost
0.490
[3]
Chemical Cost
0.074
Other Charges
0.254
Fixed Charges
$1.712
Total
1 Assumes production of 25.0 MGD per day for 365 days. 2 Includes an estimated $0.011 per one thousand gallons associated with additional compliance monitoring. 3 Estimated based on proforma existing electric standard rates.
THE OPERATOR’S FEE The O&M Agreement provides for the compensation to be paid by Tampa Bay Desal to Covanta Water for the delivery of Product Water. Covanta Water ’s fee structure is a mirror image of Tamp Bay Desal’s fee structure and consequently also consists of a Base Compensation Rate, the Excess Production Compensation Rate, the Standby Compensation Rate and/on the Long Term Standby Rates and Additional Fee Components. The method for determining these fee component are established in the O&M Agreement. Base Compensation Rate The Base Compensation Rate, expressed in $/thousand gallons, consists of Fixed Charges, Power Cost Escalated Charges, Chemical Cost Escalated Charges and Other Escalated Charges. Certain items within the Base Compensation rate, such as debt recovery and additional compliance monitoring, remain the same over the life of the contract. However, other costs identified as fixed costs, such as membrane replacement and property taxes, fluctuate over time. Electric Power Arrangements and Costs Pursuant to the WPA, the unit electrical power rate is a pass-through from Tampa Bay Desal to Tampa Bay Water, and is based on the lowest rate available to Tampa Bay Desal consistent with the WPA.
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
The cost of power is a function of the rates charged by Tampa Electric Company (“TECO”) and the amount of capacity and energy used by the Water Developer. The costs associated with rates charged by TECO are passed through to Tampa Bay Water. The capacity and energy usage in kWh per 1,000 gallons of water is guaranteed by Tampa Bay Desal and remains fixed over the life of the WPA. Short Term and Long Term Standby Compensation Rate In the case of a Short Term Standby, the Standby Compensation Rate is applicable to the difference between 25 MGD and the amount of water actually delivered. In the case of a Long Term Standby, the Standby Compensation Rate is adjusted by subtracting those operation and maintenance components included therein and by adding certain costs incurred by Tampa Bay Desal as a result of the Long Term Standby. Performance Guarantees The O&M Agreement provides, among other things, that Covanta Water will provide Tampa Bay Desal with an O&M Performance Bond (“Performance Bond”) to ensure performance of the terms and conditions set forth in the O&M Agreement. The Performance Bond is anticipated to be in place for a period of one to three years Further assurance of the Operator’s performance of the terms and conditions set forth in the O&M Agreement is provided through a Parent Guaranty. Pursuant to the Parent Guaranty, Covanta Energy Group, Inc. agrees to absolutely and unconditionally guarantee “…the full and prompt performance of all obligations of the [Covanta Water Systems of Tampa Bay, Inc.]… under the [O&M] Agreement in accordance with the terms and conditions therein, except as released or excused thereunder.”
Key Project Technical Issues RAW WATER QUALITY CHARACTERIZATION In a DBOOT project an accurate characterization of the raw water quality is important for two reasons: (1) it provides a firm basis for establishing the process design, and, (2) it allows various contractual commitments to be firmly established with an identifiable risk. The ambient raw water quality values for design purposes should be proposed on the basis of well researched and/or supported values and the best professional judgment by the designer of the variance to be expected of the water quality resulting from non-Force Majeure seasonal, storm, and drought conditions. These constituents were important to fully assess the potential for reverse osmosis membrane fouling and the capability of the treatment system to produce water that meets the Product Water Quality Standards.”
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
Covanta Water has indicated that they are presently conducting some additional specific sampling of the raw seawater to validate the original characterization of the inlet raw water quality for a number of parameters pertinent to the performance of the project. POTENTIAL FOR DISINFECTION BYPRODUCT FORMATION USING PRECHLORINATION A Bromide Study, which was undertaken by Tampa Bay Desal in November 1999, indicated that the prechlorination of raw water to prevent biofouling with 3 mg/L of free chlorine could result in the formation of considerable concentrations of two DBPs, trihalomethanes and haloacetic acids, that would exceed the current USEPA’s Stage 1 Disinfectants/Disinfection Byproduct Rule maximum contaminate levels (“MCLs”) of 80 mg/L and 60 mg/L. The current design anticipates a high removal rate of DBPs, and haloacetic acids. Covanta Water is currently validating the final selected membrane’s ability to effectively remove sufficient amounts of these chemicals or their precursors compounds to assure compliance with the current regulations. INTAKE COOLING WATER The RO membrane planned for use by Tampa Bay Desal is recommended for use at temperatures not exceeding 40°C. Tampa Bay Desal found based on temperature evaluation of power plant discharge specifically at the location of the raw water inlet that a raw cooling system would be needed to keep the temperature of the raw water below this limit. Tampa Bay Desal has indicated that the cooling system withdrawals would be needed between 8 and 24 percent of the year depending on typical annual temperature variations. Typically, the cooling water system could be needed from May through October, with August and September serving as the prime months for its use. PRODUCT WATER STABILIZATION AND DISINFECTION RO systems remove a majority of the water’s alkalinity. Consequently, historically RO treatment systems have experienced corrosion problems in their distribution systems. The stabilization of the Product Water is required to prevent deterioration of the transfer pipeline and appurtenances due to corrosion. Corrosion occurs due to the materials in contact with the water dissolving into the water. The corrosion byproducts, in turn, can be contributed to the Product Water, thereby diminishing its quality. The process proposed for chemical conditioning for stabilization and disinfection of the Product Water with lime and sodium hypochlorite had to be included by Tampa Bay Desal. The corrosion control presented by Covanta Water was based on the concept of placement of an inert film at the solid-water interface. The film is formed from the chemical deposition of calcium carbonate (“CaCO3”) from the addition of lime to the Product Water. CaCO3 films form when the water is chemically oversaturated with respect to CaCO3. The original sequence proposed by Covanta Water was lime feed into the Product Water transfer pipeline followed by chlorine addition. This concept was subsequently revised to reduce the potential for occlusion of the Product Water transfer pipeline due to accumulation of calcium carbonate (“CaCO3”). The revision include relocating the lime feed to before the on-site Product Water storage tank and providing a static mixer for the lime to promote controlled mixing.
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
Lessons Learned ADVANTAGES OF DBOOT PROCUREMENT The advantages of a DBOOT project delivery approach that we have found can be accomplished from a well-conceived procurement are: Reduce delivery schedule Competitive long term cost - Capital - Life cycle Access to design and technology innovation Access to operational experience Technology and Performance Risk Mitigation Opportunity for Informed Public Policy Decision: - Water quality vs. Incremental cost
n n
n n n n
APPLICABILITY OF ALTERNATIVE PROJECT DELIVERY METHODS Each project opportunity should be looked at carefully to assess it is a good fit for a public-private partnership. Agencies should know their strengths and weaknesses, their core competencies and risk appetites and determine which procurement method bests assures the desired outcome. The key issues that we have found that each agency will have to assess when considering the use of an alternative procurement: § § § § §
Project Costs Guarantees/Assurances Institutional Issues (water demand, water quality, schedule needs, privatization, etc.) Schedule and Performance Risk Mitigation Technology
COMMUNICATION One of the keys to the Tampa Bay Water project was the extent of the communication in the proposal process. Solicit proposer input early and often. Solicit input from short listed firms before RFP, separately if allowable. INCLUDE FULLEST DISCLOSURE OF THE CONTRACT TERMS IN RFQ AND RFP A key to executing alternative delivery projects on time and in assuring that you get the desired outcomes is to establish as early on as possible what the contractual terms and
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Tampa Bay Seawater Desalination DBOOT Project: Lessons Learned
conditions are and communicating these to the prospective vendors. If possible even include a draft of the full contract for the vendor in the RFP. OWNER/CONTRACTOR RELATIONSHIP Willingness of the owner agency and the vendor that will be developing the project to collaborate is critical to the project success. When evaluating vendors you should be aware that it is the knowledge, experience and interpersonal skills of individuals involved, not the organizations that count in making a project a success. Authors: Donald E. Lindeman, Project Manager, Tampa Bay Water, 2535 Landmark Drive, Suite 211 Clearwater, FL E-mail:
[email protected] Neil Callahan, Principle R.W. Beck, Inc., PO Box 9344 Framingham, MA E-mail:
[email protected]
157
Seawater Desalination Plant at Sandy Lane, Barbados by William T. Andrews, Managing Director, DesalCo Ltd. Derek Woolley, Engineering Manager, DesalCo Ltd. Marinus Barendsen, Operations Manager, DesalCo (Barbados) Ltd. Andrew P. Hutchinson, Principal, Associated Consulting Engineers Ltd. Abstract A 5,000 m3/day (1,320,000 US gal/day) seawater reverse osmosis plant has been constructed to provide desalinated water to Sandy Lane Properties Ltd in Barbados. The plant was commissioned in December 2000. The manufacturer of the plant will operate the plant for the initial 5 years. The plant incorporates many interesting design features, including underground construction below a tennis court, and DesalCo’s dual work exchanger energy recovery technology. This highly efficient energy recovery system, allows for a very low guaranteed overall plant specific energy consumption of 3.28 kWh/m3. The design of the plant is presented, as well as a summary of the operating experience to date. The plant was commissioned on December 23rd 2000, and having passed the performance test on January 19th 2001, has operated satisfactorily to date, despite higher feedwater salinity than expected, due to brine re-circulation. Keywords Seawater Reverse Osmosis Energy-Recovery Work-Exchanger Irrigation 1. The Contracts In early 1997, Sandy Lane Properties Ltd. (“Sandy Lane”) announced tenders for construction and operation of a seawater desalination plant of 5,000 m3/day, expandable to 7,500 m3/day, to be built at Sandy Lane Golf Course. Contracts were awarded to DesalCo Limited (“DesalCo”) in June 1999. The construction schedule for substantial completion was agreed at 39 weeks. The plant was designed, supplied, installed and commissioned by DesalCo. Sandy Lane provided all civil works, including feed and brine boreholes. The plant is specified to provide product water for the irrigation of a golf course facility, conforming to the following specifications: pH > 6.0 Total Dissolved Solids < 520 mg/l Chloride < 300 mg/l as ion Hydrogen Sulfide (same as feedwater)
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Seawater Desalination Plant at Sandy Lane, Barbados
The agreement also specified a guaranteed specific electrical consumption of less than 3.28 kWh/m3. Under a separate Operations Contract, DesalCo provides complete operations and maintenance services for 5 years. 2. Overall Plant Design The adopted design is a single stage RO system consisting of two parallel running RO trains each with a capacity of 2,500 m3/ day. Each train has its own associated HP feed pump and DWEER energy-recovery system. There is room within the plant building for a third parallel train, to accommodate the possible expansion to a total production capacity of 7,500 m3/ day. The original plant location was rejected due to its proximity to residential properties. The final location is somewhat unusual. Constructed under a tennis court, the plant is completely hidden from view, and all outside equipment is buried. The location of the feed wells is also atypical in that they are approximately 0.5 km inland and at an elevation of 15 metres. Figure 1 shows the process flow schematic for the plant (depicted as if a single train). Cartridge Filters (2)
Centrifugal Pumps (2)
2
Re-circulation Pumps (2)
1 Seawater Boreholes (2+1)
3
5 6
RO Membrane Trains (2)
8
Product Storage & Distribution
4 Work Exchangers (2)
7
Brine Boreholes (1+1)
Figure 1 – Plant Summary Process Flow Schematic
The parameters of each major stream with the plant operating at design production rate of 5,000 m3/day are shown in Table 1. The plant has the following major systems Seawater Boreholes: The plant, at 5,000 m3/day capacity, operates with two seawater boreholes. Two additional seawater boreholes are available as online spares. The seawater boreholes are cased with PVC and grouted to a depth of ~65 metres to ensure that the extraction zone is located well beneath the fresh water lens. The Island is primarily limestone with numerous cavities and caverns. Aquifer transmissivity is extremely high, and drawdown within the casing and the aquifer are negligible. Silt Density Indices are in the range of 3 to 5. The feed water has a composition similar to seawater with the exception of the low dissolved oxygen and some hydrogen sulfide.
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Seawater Desalination Plant at Sandy Lane, Barbados
Stream
Description
Flowrate Pressure 3
(m /hr)
(bar)
TDS (mg/l)
1
Raw Feedwater
583
3.1
34,426
2
PD Pump Flow
217
2.1
34,426
3
RO Membrane Feed
496
55.9
34,426
4
RO Membrane Brine
288
54.1
59,107
5
ER to Re-circulation Pump
279
53.0
34,426
6
ER Feedwater Fill
366
2.1
34,426
7
ER to Brine Disposal
375
0.3
53,269
8
RO Product to Clearwell
209
0.0
520
Table 1 - Plant major stream operating conditions
Cartridge Filters and Pretreatment: Two FRP cartridge vessels were provided, and expansion capability is available for one additional vessel. Each housing is loaded with 80 each, 40” long, 5 µ wound depth-type filter elements. The plant does not utilize any pretreatment chemicals (e.g, anti-scalants). RO Trains: Each of the two RO trains consists of 34 each 8” membrane vessels. The 7-element vessels house Dow Filmtec seawater membranes. The plant is designed to operate at a total plant conversion of 36%, with a design membrane feed pressure of approximately 56 bar. High-pressure brine energy is recovered on each train using DesalCo’s dual work exchanger energy recovery (“DWEER”) technology. The efficiency of these systems 95%, allowing for very efficient operation of the plant. The two DWEER systems are located beneath the two membrane racks, one below each rack. This minimizes piping and results in a compact membrane train design (see Figure 2). Control of each work exchanger is accomplished by use of a patented hydraulically actuated linear spool valve (LinX ValveÔ). This system has been recently developed to simplify the operation of work exchangers and to ensure that their control is more reliable (see Figure 3). Each RO train is outfitted with a high-pressure pump. These pumps are duplex stainless steel horizontal split-case centrifugal pumps.
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Seawater Desalination Plant at Sandy Lane, Barbados
Figure 2 - Membrane train with energy recovery & HP Pump
Plant Product System and Effluent Disposal System The plant product is passed directly to a product clearwell, and then pumped with vertical turbine pumps to the Sandy Lane golf course lakes, from which irrigation pumps extract the water. The plant effluent disposal system consists of the brine injection boreholes (one operational and one stand-by), and the miscellaneous effluent collection and pump system. The boreholes were constructed using the same techniques as the seawater extraction boreholes, with the exception that the uncased open hole is located at a greater depth. The miscellaneous effluent collection and pump system disposes of indoor plant drainage.
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Seawater Desalination Plant at Sandy Lane, Barbados
Figure 3 - View of LinXTM valve and membrane rack
Ancillary Systems These include a computer control and data acquisition system, which allows the plant to operate unattended. Instrumentation is connected via marshalling cabinets to the main controls I/O cabinet located in the control room. A dial-out box is available to call out in case of alarm during non-working hours. Trenches and all tanks are monitored with highlevel switches. Civil Works The plant is located within the Sandy Lane resort complex, requiring special attention to sound emissions. Minimal sound emissions result from the plant being constructed underground, with all rotating equipment, except for the submersible boreholes pumps, located within the building walls. This design keeps plant noise to a minimum and also aids in keeping the building secure. The plant normally operates unattended. The building is constructed of concrete with a pre-formed concrete roof. This heavy construction reduces sound loss from the building and is very resistant to hurricane damage. The plant consists of a hall capable of housing three RO trains for an ultimate expansion capability of the plant to 7,500 m3/day. A product room, control room, workshop, lavatory, and stores complete the building. 3. Plant Energy Consumption Table 2 illustrates the electrical consumption of the complete plant running at 5,000 m3/day, except for the product transfer pumps.
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Seawater Desalination Plant at Sandy Lane, Barbados
Equipment
Quantity
Total Load
Description
(kW)
Seawater Borehole Pumps
2
112.6
E/R Re-circulation Pumps
2
29.7
High Pressure Pump
2
415.4
Ventilation
--
4.8
Control system
--
5.0
Miscellaneous Loads
--
18.5
Contract Contingency
--
29.0
Total Electric Load Specific Electricity (kWh/m3)
683.3 3.28
Table 2 - Plant Electricity Usage
4. Operating Experience The plant was commissioned on December 23rd 2000 and the performance test was passed on January 19th 2001. The plant met all it’s performance criteria, in spite of the feed water salinity being higher than the design basis. The plant has performed well with few problems. The major difficulty has been feedwater, which has caused rapid fouling on the cartridge filters which has lead to far more frequent filter changes than expected. The unusually high horizontal permeability resulted in brine re-circulation to the feed boreholes, which commenced three months into the operation phase. New brine wells have now been constructed further from the plant and closer to the ocean. The new brine wells were only recently commissioned and there is insufficient data to determine if the relocation was successful. Mechanically the plant has performed well. During commissioning one of the high-pressure pumps developed a vibration that was attributed to a cracked impellor. The pump supplier provided an on-site technician who replaced the pump rotating assembly and the pump has subsequently performed well. 5. Conclusion The plant will provide Sandy Lane Properties Ltd, with the contracted 5,000 m3/day of product water. The plant is somewhat unusual, in that it is built under a tennis court. The high efficiency of the energy recovery system, allows for a very low guaranteed overall plant specific energy consumption of 3.28 kWh/m3. The plant was commissioned on December 23rd 2000, and having passed the performance test on January 19th 2001, has operated
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Seawater Desalination Plant at Sandy Lane, Barbados
satisfactorily to date, despite higher feed water salinity, due to brine re-circulation, which has now been addressed.
Authors: William T. Andrews, Managing Director Derek Woolley, Engineering Manager DesalCo Ltd., 48 Par-la-Ville Road-Suite 381, Hamilton HM11, Bermuda Tel: (441) 292-2060 Fax: (441) 292-2024 E-mail:
[email protected],
[email protected] Marinus Barendsen, Operations Manager DesalCo (Barbados) Ltd., P.O. Box 3087 S, St James P.O., Barbados Tel: (242) 432-7869 Fax:(242) 432-0499 E-mail:
[email protected] Andrew P. Hutchinson, Principal Associated Consulting Engineers Ltd., Winslow House, Black Rock, St. Michael, Barbados Tel: (242) 425-8505 Fax: (242) 417-9560 E-mail:
[email protected]
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The Cayman Islands’ 12-year History of Municipal SWRO Plants Operating Under Build-Own-Operate-Transfer Agreements by Kenneth Crowley, Operations Manager, DesalCo Ltd. Gerard Pereira, Operations Manager, Ocean Conversion (Cayman) Ltd. Abstract The Cayman Islands was one of the first countries in the word to fully embrace Seawater Reverse Osmosis (SWRO) provided by Build-Own-Operate-Transfer (“BOOT”) Agreements for municipal water supply. Cayman’s first such plant, with a capacity of 220 m3/day, was installed in 1989. The ownership of this plant was transferred in 1996. Today, there are 3 plants operating under BOOT Agreements, with a combined capacity of 12,600 m3/day, which represents approximately 82% of the municipal water supply in the Cayman Islands. A fourth plant, with an initial capacity of 3,000 m3/day is scheduled to start production early in 2002. The significant growth in capacity is due to the rapid development of the Cayman Islands, and the lack of natural water supplies. This paper describes the process designs of the current BOOT plants, and their history of production, energy consumption and reliability. Keywords BOOT Reverse Osmosis Energy-Recovery Work-Exchanger 1. Introduction The municipal water supply for the Cayman Islands is defined as the water distributed by either the Water Authority-Cayman or Consolidated Water Company (Cayman Water Company). These are the only two entities permitted by the Government to distribute water via pipeline to the public or to water truckers. The BOOT plants described in this paper are all SWRO plants operated by Ocean Conversion (Cayman). Since 1989, several seawater distillation plants, one of which operated under a BOO agreement, have ceased operation. In 1995 Consolidated Water Company began operation of a SWRO plant in West Bayb, Grand Cayman. This plant has since been expanded and continues to operate, but not under a BOOT agreement. In addition, several hotel and apartment properties on Grand Cayman utilize SWRO plants, but these are either not operated under BOOT agreements or do not contribute to the municipal water supply.
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2. Plant Descriptions The first BOOT plant was installed on Grand Cayman in 1989 and had a capacity of 220 m3/day. Agreements to build two larger plants, one in Governor’s Harbour, the other on Red Gate Road, with initial capacities of 2,560 m3/day and 1,330 m3/day respectively were also signed that year. Production of water from these larger plants began in January 1990. The 220 m3/day plant was moved from Grand Cayman to Cayman Brac in 1991 and ownership transferred to the Water Authority-Cayman in 1996 (the “T” in BOOT). The Governor’s Harbour and Red Gate Road plants were both expanded several times since their initial startup and currently have capacities of 4,600 m3/day and 5,000 m3/day, respectively. Ownership transfer of the Governor’s Harbour plant is currently scheduled for December 2004, and transfer of the Red Gate Road plant is currently scheduled for November, 2008. An additional plant was installed in Lower Valleya, Grand Cayman and began operation in 1998. This plant was expanded in 1999, and currently has a capacity of 3,000 m3/day. Transfer of ownership of this plant is scheduled for 2006. Demand for water in the Cayman Islands has increased dramatically since the first BOOT plants were installed. Figure 1 illustrates the increase in installed capacity of BOOT plants and the increase in water production from these plants. m 3 / year
5,000,000 4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 1,000,000 500,000 0 1990
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Figure 1 –Municipal SWRO BOOT Plants in the Cayman Islands 3. Plant Process Design The three plants currently operating on Grand Cayman are all of similar design and incorporate the following design features:
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Feed water is obtained from boreholes.
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316 stainless steel high pressure piping.
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8” spiral wound membrane elements in 6- or 7-element vessels.
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Membrane feed pressures between 58.5 and 70 bar.
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Conversion between 40 - 43 %.
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Positive-displacement pumps are used as the main high pressure pumps.
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Dual Work-Exchanger Energy-Recovery (“DWEER”) systems c.
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Degasifier / Scrubber systems for removal of hydrogen sulfide (“H2S”) from the product stream.
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Two of the plants have partial second pass systems in operation.
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One of the plants utilizes diesel engines to drive the positive-displacement pumps.
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Computer control systems.
A schematic of the overall plant process and a more detailed schematic of the RO units with energy-recovery are shown in Figure 2 and Figure 3, respectively . H2SO4 Addition
Feedwater Boreholes
Cartridge Filters
NaOH Vent Addition
Air
Degasifier & Scrubber
RO Units
Scrubber Blowdown Brine Borehole Figure 2 Overall Plant Process
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High Pressure Pump
Membrane Array
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Low Pressure Feed Water
High Pressure Brine
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Figure 3 RO units with energy-recovery 4. Feed Water Supply and Pretreatment All three plants obtain their feed water from boreholes, ranging in depth from approximately 30 to 60 metres below ground level. The water from these boreholes is of good quality, with these basic qualities: Total Dissolved Solids Silt Density Index Dissolved Oxygen Hydrogen sulfide
≈ 38,000 mg/l <1 0.0 mg/l ≈ 5-12 mg/l
Figure 4 – Feed Water Qualities Pretreatment of the feed water consists of 5 micron polypropylene cartridge filtration. No chemical pretreatment is used. 5. High Pressure Piping All the high pressure piping in the plants is constructed of 316 stainless steel. There has been no corrosion of the piping due to the lack of dissolved oxygen in the feed water. 6. High Pressure Pumps The original pumps installed in 1989 in the Governor’s Harbour and Red Gate Road plants were multi-stage centrifugal pumps. During expansions of these plants in 1994
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The Cayman Islands’ 12-year History of Municipal SWRO Plants Operating Under Build-Own-OperateTransfer Agreements
and 1995, quintiplex positive-displacement pumps were installed. The centrifugal pumps were retained as stand-by pumps, and in the case of the Red Gate Road plant, to be used in conjunction with the positive-displacement pumps during temporary expansions of the plant during the high seasonal demand periods of 1997 and 1998. Replacing the centrifugal pumps with more efficient positive-displacement pumps resulted in a significant reduction in the specific energy requirements of the plants. This reduction can be seen in Figure 5. However, positive-displacement pumps are not without their drawbacks. Some of the issues faced were: ·
Vibration required installation of additional pulsation dampeners and redesign of the pump discharge piping.
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Disposal of both the fluid-end and power-end packing leakage.
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Increased maintenance requirements.
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Noise control.
7. Energy-Recovery Systems All three plants on Grand Cayman utilize work-exchanger energy-recovery systems. The design of the work-exchanger and valves has evolved over the past ten years with the current design utilizing a DWEER system in conjunction with a LinX d valve. The combination of positive-displacement pumps and the DWEER systems results in the plants operating with the lowest possible energy requirements. Figure 5 shows the actual specific energy usage of the plants over the past 10 years. This graph displays the total energy used by the plant in kilowatt-hours divided by the actual production delivered to the reservoirs. The energy component includes all the energy used by the plant, including that used by the feed water pumps, product transfer pumps, degasifier, scrubber, air conditioning, lighting, air compressors etc. In the case of the Red Gate plant, where diesel engines are utilized, the gallons of diesel fuel used were converted to an equivalent kilowatt-hour number.
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Specific Electricity kWhr/cu.m
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Figure 5- Specific Electricity-Individual Plants The design of the work-exchanger energy-recovery system evolved over the operating period of the plants. The initial design utilized two sets of membrane pressure vessels as the work-exchangers and eight valves used to pressurize, depressurize, and switch between the sets of vessels. Polyethylene plugs were used in the work-exchangers as a barrier between the feed water and brine. The problems with this early design included: ·
Fatigue failures of the stainless steel manifolds used to connect the pressure vessels.
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Leaks in the fiberglass pressure vessels caused by wear of the plugs.
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High maintenance requirements and intermittent failures of the eight valves used to pressurize, depressurize, and switch between the work-exchangers.
These problems were solved by replacing the fiberglass vessels with the DWEER system incorporating the LinX valve developed and patented by DesalCo. Figure 6 and Figure 7 are photographs of the original energy-recovery system and of a current energy-recovery system.
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Figure 6 - Original Energy-Recovery System- Red Gate
Figure 7-Current Energy-Recovery System-Lower Valley 8. Degasifier / Scrubber System The presence of H2S in the water requires that an air-stripping tower be used to remove the H2S from the product water. Acid is added to the product water before it enters the stripping tower to convert HS- to H2S. As the water trickles down through the packing in the tower, air is forced up the tower and the H2S is removed from the water. The H2S laden air effluent from the tower is then processed through an odor scrubbing tower, which uses a caustic soda solution to absorb the H2S in a waste water stream. The original systems utilized a batch process, but this was changed to a “feed and bleed” system to improve reliability and performance. The degasifier and scrubber work in conjunction to remove the H2S from product water and prevent foul smelling H2S laden air from being emitted from the plant.
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9. Diesel Engines As part of the Red Gate Road plant expansion in 1994, diesel engines were installed to drive the positive-displacement pumps. The engines are Caterpillar 3408 engines and are connected to the pump via a clutch and gear box. While the diesel engines dramatically reduce the electricity consumption of the plant and thus provide a large cost savings, there are some drawbacks. These include: ·
Increased maintenance requirements.
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A need for additional staff skilled in the repair of diesel engines.
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Increased noise, which must be dealt with in the building design.
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Fuel storage and oil disposal.
The original electrically-driven centrifugal pumps act as stand-by pumps to the dieseldriven positive-displacement pumps. This stand-by system has been instrumental in maintaining production requirements during both scheduled and unscheduled shutdowns. The centrifugal pumps allow the plant to produce water (though at lower quantities and at increased cost) while maintenance is performed on the engines and pumps. 10. Computer Control System Each plant utilizes a computer control system to continuously monitor the operation of the plant and to records data on a regular basis. The plants are only manned during normal working hours (8:00am-5:00pm), Monday through Friday. If a problem develops at night or on the weekend, the computer will decide if the entire plant needs to be shutdown, or just part of the plant, and will notify a plant operator via pager. The system is comprised of two main parts. The software and the interface between the software and the instruments and equipment. The original software installed in 1989 required two dedicated, specially modified, Apple Macintosh computers. The software has been changed and upgraded several times to keep pace with the rapid improvements in technology that has occurred during the past decade. Today the software that controls the plant is Windows-based and runs on a personal computer which can concurrently run additional software programs. 11. Conclusion The Cayman Islands have successfully utilized BOOT Seawater Reverse Osmosis Plants to provide the public with high quality potable water. Since 1989, when the first BOOT plant was installed, demand for potable water has increased rapidly. It is a credit to the good planning on the part of the water distributors and the partnership that has been forged between water distributors and the BOOT suppliers that water production has increased in step with demand and that the public has been, and will continue to be, supplied with an adequate supply of high quality potable water.
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12. References: a. W.T. Andrews, K. Crowley, R. McTaggart, S.A. Shumway, and D. Woolley, Installation of a New Seawater Desalination Plant at Lower Valley, Grand Cayman, The Next Breakthrough in Seawater Desalination, Curacao, Netherlands Antilles, June 1998. b. W.T. Andrews et al, Energy Performance Enhancements of a 950 m3/d Seawater Reverse Osmosis Unit in Grand Cayman, Seawater Desalination Technologies on the Threshold of the New Millennium, Kuwait, November, 2000. c. S.A. Shumway, The Work Exchanger for SWRO Energy Recovery, International Desalination & Water Reuse Quarterly, Feb/Mar 1999, Vol 8 No 4, pp. 27-33. d. S.A. Shumway, Linear Spool Valve Device for Work Exchanger System, U.S. Patent 5,797,429, August 1998.
Authors: Kenneth Crowley, Operations Manager, DesalCo Ltd., 48 Par-la-Ville Road-Suite 381, Hamilton HM11, Bermuda. Tel: (441) 292-2060 Fax:(441) 292-2024 E-mail:
[email protected] Gerard Pereira, Operations Manager, Ocean Conversion (Cayman) Ltd., P.O. Box 30614 SMB, Grand Cayman, Cayman Islands Tel: (345) 945-5105 Fax: (345) 945-5106 E-mail:
[email protected]
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“The Modern Day Rain Maker” By Sea Solar Power by Robert Nicholson, President Sea Solar Power International
It is a special pleasure to be part of this conference because it is the first time Sea Solar Power has made a presentation to the water industry. My purpose is to introduce you to an emerging and promising new technology for converting seawater into fresh water. This is primarily an opportunity to explain the concept so that you can grasp the big picture. It is not a situation where I want to overwhelm you with fine details. Hopefully, each of you will leave having gained a general understanding of how this technology works and how it could benefit you, your business and your community. I also want to emphasize that this is not a solution for everyone’s water shortage. It is merely another option for communities in need of fresh water that are located near the equatorial zone. With underground water tables rapidly declining all over the world there will be a demand for all types of desalination systems. The technology is known as ocean thermal energy conversion or OTEC (Ref. 1). It generates baseload electricity and produces large quantities of desalinated water using only solar energy. The heat is stored in the upper layers of the tropical ocean and is available throughout the equatorial zone (Fig. 1). It may be helpful to mention several fundamental facts related to OTEC for you to gain a better understanding of this enormous resource (Ref. 2)! The ocean can provide, from just the equatorial zone, 300 times the electricity that the world now consumes and at the same time produce an abundance of high quality fresh water. Another interesting fact is that when a pound of water is raised to higher temperatures it is equivalent to lifting it to a height of 778 feet. The OTEC cycle operates on a delta T of 40 degrees F. so by multiplying 40 X 778 equals 31,120 feet. Best possible Carnot Cycle designed by SSP, for an OTEC plant, is about 3.25% which when multiplied by 31,120 equals 1,011 feet. Since the power cycle is pumping warm and cold water we must divide 1,011 by 2 which creates a head of water that is approximately 500 feet high (Ref. 3). Furthermore, this source of energy is baseload meaning that it is available 24 hours per day. Unlike a hydro dam in the summer time when electricity is needed the most an OTEC plant generates its highest output because of a greater delta T. The upper layers of the ocean are at their warmest temperature during the summer, providing ideal operating conditions. The solar heated surface water of the tropical ocean serves as the heat source and the deep cold bottom ocean water as the heat sink. A heat machine (Fig. 2) at the surface pumps the warm water through a series of evaporators to convert the working fluid propylene from a liquid to a gas which expands through vapor turbines that drive the generators. The cold
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water is pumped up from the bottom of the ocean which is used to chill or condense the gas back into its liquid state. The system is charged with propylene, a working fluid similar to isobutane, freon or ammonia which are commonly used in organic vapor cycles (Ref. 4) Propylene boils at 67 degrees F under pressure of 130 psig. The solar heated surface water within the equatorial zone is a constant 80 degrees F. The cold bottom water, typically at 3,000 feet, is a constant 40 degrees F creating a delta T of 40 degrees which is sufficient to drive vapor turbines (Fig. 3). The original cycle was designed to remove 50% of the oxygen out of warm incoming water to prevent marine life from growing on the inside of the heat exchanger tubes. This would create a water vapor that when passed over cold surface areas would condense into pure water. This process produced about 5 million gallons of fresh water per day. However, to assure greater heat transfer for a longer period of time this part of the cycle was expanded. Now, all of the warm water is pumped through a deaeration system in stages so that 99.9% of the gases are removed. At this point the water is converted into steam which transfers the heat of condensations to the working fluid propylene. The result is better heat transfer and large quantities of fresh water. SSP has designed 2 standard commercial models consisting of a small 10 MW land based OTEC plant (Fig. 4) and a large 100 MW floating plantship (Fig. 5). The land based plants generate 10 MW’s of net power and 3 million gallons of fresh water per day (Ref. 5). If desired, the plant can be dedicated to produce only fresh water at the rate of 10 million gallons per day. The floating plantship (Fig. 6) will generate 100 MW’s of net power and 32 million gallons of fresh water per day (Ref. 6). The plantship when dedicated to desalination will produce 130 million gallons of fresh water per day. Each plantship will create an annual fish harvest of at least $50 million (Ref. 7). This is because of the cold nutrient rich water pumped up from the bottom which creates plankton at the surface and when subjected to sun light produces a large source of fish food. In addition, large commercial quantities of fish and vegetables can be grown in the effluent of a land based OTEC plant. The land based plant has the advantage of operating large holding tanks adjacent to the OTEC plant. Food production takes place because of the nutrient rich water pumped up from the bottom of the ocean and the ability to control the temperature of the water. For example, tomatoes and lettuce can grow 3 times faster in this environment compared to conventional farming in soil. It is also important to recognize that many tropical economies are void of rich topsoil and often lack the proper quantity of rain to produce high yields. Another unique opportunity is the raising of salmon which are typically grown in cold climates. SSP has a proposal to Guam for a 10 MW land based plant and is working with a group who are proposing to operate a salmon farm next to the OTEC facility. SSP can supply them with tempered water ideally suited for raising salmon. In addition, the cold water
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effluent from the OTEC plant can be circulated through the building providing low cost refrigeration and air conditioning for the fish packing plant. The farm will produce about $18 million of fish per year and employ over 120 workers (Ref. 8). Furthermore, the OTEC experience in Hawaii conducted by the US Department of Energy has proven the success of an OTEC park in spite of the failure of the plant itself. The park started out with 300 acres surrounding the experimental OTEC plant to take advantage of the cold water being pumped up from the bottom of the ocean. The State of Hawaii (Ref. 9) continues to operate the cold water pipe by simply buying energy to operate the pumps. This is because the entrepreneurs using the nutrient rich cold water have rapidly expanded requiring 800 additional acres for mariculture. Operating an economically efficient OTEC plant on a commercial basis will provide an enormous amount of nutrient rich and tempered water creating a diversified opportunity for economic development. Many tropical island economies must import much of their basic commodities therefore, Sea Solar Power will allow these communities to become more selfsufficient. Because this technology is new to most of you it will be interesting to provide some historical background. It was invented by the French in 1881 and a commercialization effort took place during the early 1900’s. But, it stems from the basic principles of refrigeration and in those days refrigeration was in its infancy. It was not until 1962 that J. Hilbert Anderson (Ref. 10) began working on OTEC as a modern day expert on refrigeration cycles. At the time Hilbert Anderson was chief engineer of York International, one of the largest refrigeration companies in the world. He left York International in 1963 to develop Sea Solar Power. Hilbert Anderson is a prolific inventor and design engineer with a BS and MS in mechanical engineering from Penn State University. He was director of R & D for Ingersoll-Rand before moving to York International. While at Ingersoll-Rand he designed steam and gas turbines, large pumps and centrifugal compressors. During the early days of W.W.II the US Army summoned all leading turbo machine designers to Manhattan to tackle a major engineering problem. When presented with the challenge all design engineers responded negatively to the task stating that the Mach numbers were impossible to achieve. However, Hilbert Anderson raised his hand explaining that he could design such a compressor. The next day the Army officials went back to Ingersoll-Rand where Hilbert Anderson demonstrated how this sophisticated machine could be designed and manufactured. Hilbert Anderson played a significant role in making it possible for the US to produce the atomic bomb for the Manhattan Project. The point that I am making is that an OTEC plant can not be economically efficient when using only standard off the shelf equipment. The size of an OTEC plant is proportional to the volume of water being pumped through the plant (Ref. 10). Think of an OTEC plant as just one large heat pump.
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Using conventional heat exchangers does not allow high transfer of low grade energy from seawater to the working fluid propylene (Ref. 10). Therefore, large heat exchanger surface areas are required necessitating the need for a large volume of both warm and cold water. Hence, a large vessel is essential to support the extra weight of the large pipes pumps and heat exchanger surface areas. The capital cost of the plant is critical even though the fuel is free. An American consortium of prominent manufactures coordinating with the Hawaii OTEC interest orchestrated by the U.S. Department of Energy failed to recognize this factor. Furthermore, they based their design approach on fossil fuel power plant parameters rather than on the principles of refrigeration as did Hilbert Anderson. Consequently, the D.O.E. and industry OTEC efforts to design a viable OTEC Cycle for commercial applications was a failure. For example, the D.O.E. OTEC design for a 100 MW plantship weighed over 200 thousand tons and cost over $2 billion to build. The plant was designed to handle 15,000 cubic feet per second of warm water and 15,000 cubic feet per second of cold water for a total of 30,000 cubic feet of water per second. The cold water pipe was 50 feet in diameter, made of concrete and weighed over 18,000 tons. In comparison, the Sea Solar Power design for a 100 MW OTEC plantship weighs only 25,000 tons or 8 times less than the D.O.E. design. This means that it costs 8 times less to build than the D.O.E. model. The D.O.E. plant would never generate enough revenue to pay for itself. The Sea Solar Power design has a simple pay back of 2-3 years (Fig. 7). In the power industry it is common practice to use smooth heat exchanger surface areas. The D.O.E. OTEC Cycle was designed with smooth surfaces obtaining a U value of only 600. The refrigeration industry has in common practice a U value of over 1200. Sea Solar Power has developed an optimized enhanced surface that exceeds a U value of over 2,000 (Ref. 11). It is made of inexpensive aluminum which is an excellent material for obtaining high heat transfer coefficient and ideally suited for OTEC (Ref. 12). Prominent engineers, economists and environmentalists have investigated the Sea Solar Power OTEC design. All have concluded in writing that the technology is fundamentally sound and economically efficient. This includes Fluor Daniel, Lehigh University’s Center for Energy Research and a $200,000 EA Engineering study paid for by The Abell Foundation, all of which confirm the economic merit of a 100 MW Sea Solar PowerOTEC plantship (Ref. 6, 13, 14). The Abell Foundation and the Rockefeller Foundation each paid Stone & Webster and Kvaerner / John Brown to evaluate Sea Solar Power’s land based OTEC plant. This in-depth study confirms the commercial merit of the land based design (Ref. 5) The manufacturing of the components that make up the cycles such as the turbines, compressors, pumps and the vessels to house the cycles are being built in Baltimore when practical. Sea Solar Power has shown top government officials of Maryland how to create
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25,000 new jobs in Baltimore when building only six plantships per year (Ref. 15). As a result the State of Maryland (Ref. 16) with matching funds from The Abell Foundation (Ref. 17) provided research dollars to build a heat exchanger test facility to prove the performance of the new heat exchangers invented by J. Hilbert Anderson and Sea Solar Power. Because the Sate of Maryland is so committed to the commercial development of Sea Solar Power experts from the University of Maryland’s school of engineering were brought in to witness the heat exchanger test. The results exceeded expectations which were confirmed by the university’s heat transfer experts in writing ( Ref. 11). This established that the technology was ready for commercial application prompting The Abell Foundation to decide to provide 100% funding for the first plants (Ref. 18). The Abell Foundation has many missions with number one being to increase their wealth so they can continue to help additional people in need. They are fully committed to making Baltimore a better city by helping to improve in areas of education, health and a special focus to expand economic development. They also want to make a contribution to solving global problems such as climate change, better water for more people and increased food production around the world. The Abell Foundation believes that Sea Solar Power can contribute to all of these missions more effectively than any other business opportunity or technological development. Therefore, The Abell Foundation which owns Sea Solar Power International plans to fund and operate OTEC plants all over the world (Ref. 19). Sea Solar Power International will offer to sell electricity, desalinated water and tempered nutrient rich water to clients throughout the equatorial zone that will be environmentally safe at very competitive prices. Sea Solar Power is proposing to the Cayman Islands to build a 10 MW land based OTEC plant offering power and water at a cost lower than the islanders can produce themselves when importing expensive foreign oil. Eventually, Sea Solar Power will sell the plants to the host client and ultimately the technology will be licensed to shipbuilders throughout the world. The developing countries alone will need 1500 gigawatts of electricity during the next 20 years. This equates to 15,000 power plants that are 100 MW’s each. The demand for desalinated water will require a large number of OTEC plants that could make an economic and environmental contribution to this growing global problem. The need to produce electricity, fresh water and food without harm to the environment is reaching critical conditions. We would like to believe that many of you in the audience will be able to join us in providing desalinated water to communities through out the equator. We ask you to help us help others!
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References 1. OTEC – A term developed to identify ocean thermal energy conversion coined by Dr. Robert Cohen of the National Science Foundation in the early 70’s 2. Calculations by J, Hilbert Anderson – modern day pioneer of OTEC 3. 778 foot pounds of work are equal to 1 BTU of heating energy. BTU is the amount of heat required to heat 1 pound of water 1 degree 4. Vapor- Turbine Cycle for Geothermal Power Generation by J. Hilbert Anderson – 1972 5. Stone & Webster, Kvaerner / John Brown Technical Assessment for 10 MW land based OTEC plant 1998 6. Feasibility Study of an 100 MW Ocean Thermal Energy Plant June 1988 for SSP by Fluor Daniel 7. Roels, Food, Energy and Fresh Water from the Deep Sea – Mechanical Engineering – June 1980 8. Gand Company, Norway – One of the largest salmon producers in the world –Joint venture with SSP under consideration 9. Natural Energy Laboratory of Hawaii board meeting attendance by SSP in Hawaii – June 1997 10. Ocean Thermal Power – The coming Energy Revolution by J. Hilbert Anderson, Solar & Wind Technology Vol. 2, No. 1 1985 11. Letter from the University of Maryland confirming test results observed by their heat transfer experts to The Abell Foundation – April 1998 12. Qualifications of Aluminum for OTEC by La Que Argonne National Laboratory – July 1979 13. Lehigh University – Review of Sea Solar Power – OTEC concept July 1988 14. EA Engineering, Science and Technology Technical and Environmental Feasibility assessment of Sea Solar Power’s OTEC – May 1990 15. Meeting with the Lt. Governor of Maryland, Kathleen Kennedy Townsend and Secretary of Economic Development, James Brady of Maryland receiving approval for HX test Facility grant - April 1998 16. Issue of Grant by the State of Maryland -August 1998
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17. Abell Foundation matching state grant for HX Test Facility Sept. 1998 18. SSP licensed it’s OTEC technology to The Abell Foundation for exclusive global application with full funding by the Abell Foundation - Jan. 2000 19. Sea Solar Power International owned by the Abell Foundation established to develop OTEC on a commercial basis – June 2000
Figures
Fig. 2
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Fig. 3
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Fig. 4
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Fig. 5
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Fig. 6
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Fig. 7
Author: Robert Nicholson, President Sea Solar Power International 111 S. Calvert Street, Suite 2300 Baltimore, Md 21201 Tel: (410) 547-1300 Fax: (410) 539-6579 E-mail:
[email protected] Website: www.seasolarpower.com
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction” by Shawn Meyer-Steele, Antonia von Gottberg, Jose Luis Talavera Ionics Incorporated – Ionics Aqua Design 1. Introduction Desalination in the Caribbean With continued population growth and an overall expansion in tourism over the last few decades, a heavy burden has been placed upon the natural resources of the Caribbean. Water, essential for life itself, is one of the resources most drastically affected, whether by overpumping of the natural sources that has sustained island nations for centuries, or the inadvertent contamination of sources through development. One of the challenges for the people of the Caribbean and their governments has been the to manage and sustain this natural resource. Most of the Caribbean, built over the millennia through the natural growth of coral reefs or volcanic eruption, does not typically have sufficient natural reservoirs, aquifers, and rain recharge that larger landmasses enjoy. The Caribbean, and the rest of the world, faces the unmistakable irony that although the world’s major surface component is made up principally of water, there is “Water, water, everywhere there is not a drop to drink”. The salinity of human blood is almost equal to that of the oceans, possibly hinting at our humble beginnings, but we would perish more quickly drinking seawater than drinking nothing at all. So we turn back to the ocean again but this time we do so with a twist. Advances in technology allow us the small miracle, that we mimic from nature, of removing enough of the salt from the water from the sea to be able to produce clean, safe, drinking water. The supply seemingly inexhaustible at first glance, it might appear that our problems are solved. But to accomplish this remarkable alchemy requires energy, and energy in the Caribbean, primarily imported, is a more dear and precious a commodity than the water it is required to produce. SEAWATER DESALINATION COSTS The next challenge comes in applying the technology as efficiently and as cost effectively as possible. The costs in seawater desalination have been reduced greatly over the last twenty years, most notably through the advances in reverse osmosis as shown in Figure 1. In 1978, the cost to produce 1,000 US gallons of potable water from seawater in a large desalination facility was over US$20. Today, the cost has decreased by a factor of six, to less than US$3 per 1,000 US gallons today.
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$ per 1,000 Gallons
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1988
1998
Figure 1: Cost of Water produced by Seawater RO 1980 – 2000 In the Caribbean and in most of the world, (except where large amounts of waste heat from true co-generation facilities are available) reverse osmosis has proven to be, by far, the most cost-effective technology for sea water desalination (1). Reverse osmosis (RO) is a pressure-driven process by which salt can be removed from seawater. If a solution containing salts is placed on one side of a semi-permeable membrane, with a more dilute solution on the other side, water will be forced by natural osmosis through the membrane from the more dilute to the concentrated side in an attempt to reach equilibrium. Reverse Osmosis utilizes external pressure to overcome the natural osmotic pressure and force water through a semi-permeable membrane from the more concentrated to the less concentrated side. RO is chosen for many desalination applications today because of its proven ability to produce high quality water in an energy efficient manner with the ability to withstand (given appropriate pre-treatment) fluctuations in feed water quality. A seawater reverse osmosis (SWRO) plant includes several major blocks, as shown in Figure 2; the site & building; feedwater supply; pretreatment; SWRO unit; post treatment; chemical systems; instrumentation; electrical & control system. The section below discusses each of these areas in more detail.
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
Chemical Storage Feedwater Supply
Ultrafiltration RO Building (UF)
Pretreatment
Concentrate Discharge
Product Reservoir
SRWO Unit
Figure 2: Typical SWRO Plant 1.1 Site and Building The site as a whole generally includes: ·
The plant building
·
Outdoors chemical storage area.
·
Production reservoir.
·
Wastewater collection and discharge system.
·
The site including civil works, paving, fencing, and landscaping.
1.2 Feed Water Supply Feed water to the desalination system is collected from a seawater intake or beach wells located as near the plant site as is possible. From the intake, a feed pump will convey feed water to the pretreatment system. 1.3 Pretreatment The seawater must be treated before it reaches the RO unit to remove suspended solids. Typically, multimedia filters are used to effectively remove solids. The filters are designed to operate at a loading rate consistent with the overall plant design. The suspended solids are removed from the water into the filtering media by a combination of mechanisms including straining, interception, impaction, sedimentation, flocculation, and adsorption. A majority of the suspended material in the raw sea water is removed during this first filtration step. Recently, there has been much interest in the application of back-washable, hollow fiber ultrafiltration systems as pretreatment for SWRO systems. Today, the capital cost is higher than with traditional media filters, but the space requirement is smaller and UF provides higher quality feedwater to the RO. Ongoing work in this area may soon provide a reduction in the cost of seawater desalination. 188
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Filtered water flows to the reverse osmosis unit. 1.4 Sea Water Reverse Osmosis Unit The core desalination operation is reverse osmosis. The process elements of a typical desalination unit are cartridge filters, an RO feed pump, an energy recovery device, an RO membrane unit, and auxiliary systems for cleaning and chemical addition. Figure 3 shows a photograph of a 3,000 m3/day (792,000 gpd) SWRO plant at KAE, Curacao, Netherland Antilles before expansion to it’s present 10,181 m3/day (2,690,000 gpd) size .
Figure 3: Photograph of SWRO unit, KAE, Curacao, N.A.
1.4.1 Cartridge Filtration Water is conveyed to the cartridge filters from the media filters. The cartridge filter system is used to remove fine suspended matter from water, typically down to 5 microns in size. A cartridge filter consists of a filter housing and filter elements mounted to tube supports. Water enters the housing and flows through the filter elements. The suspended solids are trapped in the fine fibers of the filter. 1.4.2 Reverse Osmosis In reverse osmosis, water under pressure is forced across a membrane element with a portion of the feed permeating the membrane and the balance of the feed water sweeping along the membrane surface and exiting without passing through the membrane. In the case of seawater, the membrane will freely pass water but will reject most of the dissolved minerals as well as any small particles. An illustration of an RO membrane element is shown in Figure 4.
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
rs Reve
osis m s eO
Permeate Concentrate
eate Perm
Pressurized Feed Water Na+ Na+ Cl -
Na+
Cl
Cl
-
Cl -
Na+
-
-
Cl Na+
ne bra m Me ne RO bra m Me RO
-
+
Cl Na
Figure 4: RO Membrane Element SWRO plants typically employ spiral wound, thin film composite polyamide membrane elements to separate dissolved salts from the seawater. In a typical one-stage SWRO system, the process can convert, or “recover” approximately forty (40) percent of the incoming seawater as desalted product. The remaining approximately sixty (60) percent of the incoming water is concentrated by the salts rejected from the product and is returned to the sea. Two-stage SWRO recover approximately sixty (60) percent of the incoming seawater as product with forty (40) percent returned to the sea. The high pressure required for RO treatment is provided by a high-pressure pump. The RO system includes a single pass of treatment in one stage. Permeate from the RO system flows to the post-treatment system. Concentrate (reject) from the RO systems flows through the energy recovery device and is then discharged back to the sea. 1.4.3 Energy Recovery The pressure required for RO treatment is provided by a high-pressure pump. Because of the relatively high energy requirements, most SWRO systems are equipped with an energy recovery device that recovers energy from the pressurized RO concentrate leaving the system. The energy recovery system typically recaptures anywhere from 20 - 50 % of the initial pumping energy.
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1.4.4 Concentrate Discharge Concentrate from the RO system is discharged back to the sea through a reject pipeline or through a deep well. This pipe is also be used for disposal of wastewater such as filter backwash. 1.4.5 Clean-In-Place System A membrane cleaning system is normally provided to clean RO membrane elements if suspended solids or precipitates foul them. Cleaning procedures are undertaken when operating pressures or RO permeate production falls outside normal operating limits. The system used to effect this cleaning (referred to as the Clean-In-Place or CIP procedure) consists of: a chemical tank; a pump to re-circulate the cleaning chemicals through the RO membranes; a cartridge filter to remove any solid contaminants or scale which is removed from the vessels and/or piping. 1.5 Post Treatment Post-treatment of the RO permeate is needed to create a potable water that is properly adjusted for storage and distribution. A calcium carbonate filter and/or caustic soda addition systems are typically provided for pH adjustment, re-mineralization. Sodium hypochlorite and/or UV sterilization are used for disinfection of the final product. After post-treatment, the product water is delivered to a production reservoir. 1.6 Chemical Systems The water treatment plant can require the addition of chemicals at certain points throughout the system, as indicated in the descriptions given in this section. The chemicals used in the plant vary depending on the water source. The chemical systems supplied depend upon the nature of the chemical used but generally consists of a chemical storage tank of suitable capacity and material of construction for the chemical under consideration, two chemical dosing pumps (main and standby) and interconnecting piping. In addition, each system will be supplied with a mixer if necessary. 1.7 Instrumentation Instrumentation typically includes: pressure gauges, pressure switches, conductivity indicators and transmitters, temperature indicators and transmitters, level indicators and switches, and flow indicators and transmitters. The system is normally equipped with sample ports so that water samples may be collected at various locations in the process. 1.8 Electrical and Control System The power and control system typically includes: ·
power distribution components, 191
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·
control panels, instrument panels, and
·
programmable control devices.
The control system typically provides for complete automatic operation of the desalination system. A central control system will control, monitor performance, and record operating data for all aspects of the desalting plant. It will provide plant-operating status, alarm messages, data collection, protective shutdowns, and automatic regulation of the plant equipment. 1.9 Advances in SWRO The developments that account for most of the advances seen in RO cost reduction over the last 20 years in Figure 1 came about on five different fronts: 1) Through the use of energy recovery devices. 2) Through new membrane chemistries that allowed for the same salt rejection >99.9 % with lower feed pressure which requires less energy and hence lower operating costs. 3) Through new membrane elements and pressure vessels that allow operation at higher pressures and hence higher salinities at similar salt rejection rates. 4) Through larger basic RO units (trains) that provided some cost reduction through economies of scale for key components such as pumps, piping, and pressure vessels. 5) Through the establishment of relationships with municipalities, whereby each side lends it’s own expertise and ability to lower the capitol and operating costs to the project. While the fourth front is valid, there have been industry-wide “growing pains” resulting from making the basic trains too large. The fifth front is very project specific. In this paper, we will limit our focus to the first three areas. When designing a SWRO system today, the engineer must decide what kind of energy recovery device to use, and whether or not to use a brine conversion system. By optimizing the system for local conditions, one can minimize the overall life-cycle costs of producing desalted water. 2. Energy Recovery Devices There are a number of devices available commercially that are capable of reducing the unit power consumption of reverse osmosis units. This is primarily accomplished by reducing the power consumption of the high-pressure pump by capturing and returning the energy in the concentrate stream (which was waste energy before the development of energy recovery devices). For typical single pass, singe stage seawater desalination the concentrate pressure can be from 55 to 65 bar (800 – 950 psi). Three of the most successful are the turbocharger, the Pelton wheel, and the work or pressure exchanger. 192
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2.1Turbocharger The turbocharger has been successfully used for SWRO energy recovery since 1989. The turbocharger essentially acts like a reverse running pump, where the RO concentrate is used to turn a turbine that is coupled to a pump section with its impeller on the turbine shaft. The energy transfer from the RO concentrate to the RO feed through the turbocharger increases the pressure of the RO feed and thus reduces the external energy requirement for the RO feed. Figure 5 illustrates the PFD of a typical RO system using a turbocharger for energy recovery.
Reverse Osmosis (RO)
Desalted Product
HP Concentrate
Filtered Water
HP Feed Pump
HP Feed
LP Concentrate
Drain
Figure 5: PFD - Turbocharger Since the turbocharger is a high-speed rotary machine it requires little maintenance. It is compact in size and low weight. The waste stream is pressurized so it can be disposed of without re-pumping being required. The nominal efficiency of the device is quite low, however, due to high viscous losses in the device. Also, flow deviations with respect to the design point, such as temperature fluctuation or change in water recovery, has a potentially large impact on performance. The turbocharger is generally used on smaller units. 2.2 Pelton Wheel Pelton wheel technology was first evaluated for energy recovery almost 20 years ago (2). The first prototype machines were based on standard hydroelectric turbine hydraulics. Development of this technology over the past two decades has led to the widespread use of Pelton wheels in SWRO systems, accounting for about 80% of energy recovery devices fitted to SWRO plants over 1 mgd capacity. A nozzle valve is used to direct a jet of high-pressure RO concentrate onto the bucket type blades of the Pelton wheel (3). This causes the wheel to turn. The kinetic energy of the jet is converted into rotating mechanical energy. By coupling the shaft of the Pelton wheel to a motor or pump, this energy can be used to reduce the electrical energy that is needed to pump the RO feedwater. Figure 6 illustrates the PFD of a typical RO system using a Pelton wheel for energy recovery. 193
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Pelton wheels are reliable and easy to maintain. Typical device efficiency ranges between 84 and 90 %. Since the discharge from a Pelton wheel is an atmospheric pressure, either the waste must be able to drain by gravity, or else it has to be re-pumped.
Filtered Sea Water
HP Feed Pump
HP Feed
RO Membrane Array
Desalted Product
Motor
Pelton Wheel ERT
Concentrate
Turbine Nozzle Control Valve
Drain
Figure 6: PFD – Pelton Wheel 2.3 Work Exchangers The original work exchanger was built for the U.S. Government in 1980. There are a number of similar products on the market. The author’s company markets their version of the work exchanger under the name “Dyprex”. The work exchanger uses a system of pistons and valves to transfer the pressure of the RO concentrate to part of the RO feed. A high-pressure booster pump then pumps this pre-pressurized feed to the required RO feed pressure. The remaining RO feed is pumped by a high pressure pump. Figure 7 illustrates the PFD of a typical RO system using a work exchanger for energy recovery. Since the work exchanger directly transfers energy from the concentrate to the feed rather that through rotating machinery, it has higher efficiency in comparison to the Pelton wheel and turbocharger. However, the work exchanger is limited in size, and, although adding units in parallel can increase capacity, the capital cost is high for large plants. Work exchangers also have a large number of moving parts that can be subject to wear. Figure 8 shows a photograph of a work exchanger at a 26,400 m3/day (360,000 gpd) SWRO plant at Handsome Bay, BVI. PEI has introduces a smaller version of a work exchanger (the Pressure exchanger) built on a principle similar to the Dyprex with less moving parts. It is marketed as having the same
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type of efficiencies but has not been adequately proven in long term operation and only used to-date on smaller plants.
Motor
Filtered Sea Water
HP Feed
HP Feed Pump
HP Concentrate
Motor
Suction Accumulator
Motor
Desalted Product
Free Floating Piston
VFD HP Feed
RO Membrane Array
HP Booster Pump
LP Feed
LP Concentrate
LP Booster Pump Pressure Tubes
Drain
Figure 7: PFD – Work Exchanger
Figure 8: Work Exchanger, Handsome Bay
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2.4 Comparison of Energy Recovery Devices When selecting the most appropriate energy recovery device for a given application, one needs to consider several factors including the cost of power, expected variation in plant operating conditions, maintenance requirements and capital cost. Table 1 compares the features of the three energy recovery devices discussed above. Note that the capital cost refers to only the capital cost of the energy recovery device; when selecting an energy recovery device in a particular application, one needs to look at the overall cost of pumps, energy recovery devices and VFDs to determine which scheme is optimum in that case. Recent innovative approaches include combining the turbocharger and Pelton wheel to minimize energy consumption and to recovery energy as efficiently as possible over a wide range of operating conditions (4). Table 1: Comparison of Energy Recovery Devices
Device
Turbocharger
Pelton Wheel
Work Exchanger
Capital Cost
Low
Low – Medium
High
Efficiency
Low (55 – 60 %)
Medium (84 – 90 %)
High (> 95%)
Efficiency Curve
Slopes downwards at lower flows
Varies
Flat
Crossleak from reject to feed
Minor via center journal bearing
Connected via motor so not an issue
Low (< 3%)
Capaccity Range
< 2.5 mgd
Up to multi mgd
< 2.5 mgd
Reliability
High speed rotary machine – easy to overhaul
High speed rotary machine – easy to overhaul
Multiple valves and other parts subject to wear
Footprint
Compact
Compact, but required civil work for atmospheric drain
Large
Discharge Pressure
Pressurized
Atmospheric
Pressurized
Effect of deviation from design point
Wide operating range
Wide operating range
Moderate impact on performance
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3. Toray Seawater Second Stage Brine Recovery Conventional wisdom has held for years that to maximize efficiency of the systems, the optimum recovery and configuration was 35 - 40 % recovery and a single stage system. It has always been apparent that the low recovery of historical SWRO meant that a lot of water had to be pretreated, then pumped to high pressure and then 60 – 65 % of this water was just dumped back to the sea. Limitation in the membrane module design, however, prevented SWRO systems from operating at higher water recoveries. As the water recovery increases, the concentration of salt in the brine stream also increases. Hence, the pressure that must be applied to overcome the osmotic pressure of the brine stream increases. Most spiral wound RO membranes can operate up to 82.7 bar (1,200 psi) at temperatures below 29 °C. If water recovery is increased, the pressure limitation of the membrane becomes a limit on recovery before any limits on water chemistry are reached. If water recovery were to be increased to the water chemistry limit rather than the membrane pressure limit, then the RO membrane had to be capable of operating at pressures up to 98 bar (1,420 psi). Toray Industries, Inc., has been manufacturing with great success for some years now a spiral wound RO membrane that can operate at high pressure and can achieve over 99.9 % rejection working on the concentrate reject from the first stage unit (5). This brine second stage system, called a Brine Conversion System (BCS), is capable of recovering an additional 50 % of the concentrate for recoveries of up to 60 % with no appreciable increases in product salinity or energy per unit of product produced. The Authors Company has formed a joint-venture company with Toray to manufacture and sell these membranes in the America’s and the Caribbean. 3.1 Single Stage versus Two Stage System Table 2 compares the performance of a conventional one stage SWRO system with that of a two stage system employing the Toray brine recovery membrane. The performance of the desalination system is based on typical Caribbean seawater composition and a process temperature of 28 °C (83 °F). As feed water conditions vary, system performance will change. Table 3 compares the relative cost of water production for a traditional single stage system and a two-stage system (6). The two stage system saves a good deal of capital costs and footprint area because the intake, outfall, the pretreatment, and the amount of seawater taken in by the intake pumps is only 67 % of that for a conventional first stage system. The energy of this second stage can be minimized by using an energy recovery device such as a turbocharger to boost the pressure of the first stage concentrate using the second stage brine. Hence, the electricity consumption of the two-stage system can be lower than that of the single stage system. These savings in water production cost can reduce the cost of desalinated seawater by 16 %. 197
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Table 2: Comparison of One and Two Stage SWRO plants
Parameter Net Production Product Salinity Salt Removal Rate Product Water Recovery Operating Temperature Operating Pressure
Performance 1 Stage 3
7,500 m /day (2 mgd) 200 – 350 mg/l TDS 99.9% + 40% 24 – 28 °C (75 – 83 °F) 55 – 62 bar (800 – 900 psi)
Performance 2 Stage 11,300 m3/day (3 mgd) 220 – 375 mg/l TDS 99.9% + 60% 24 – 28 °C (75 – 83 °F) 76 – 83 bar (1100 – 1200 psi)
Table 3: Comparison of Water Production Cost
%
1 Stage
2 Stage
Capital Cost Electricity Membrane Replacement Chemicals Other (Labor, maintenance, etc) Savings
46 % 36 % 5% 4% 9%
37 % 30 % 6% 2.5 % 8.5 %
-
16 %
Case Study 1: Maspalomas II SWRO Plant The authors’ company owns and operates this 20,400 m3/day SWRO plant as well as a 20,000 m3/day electrodialysis reversal (EDR) plant for brackish water desalting. The facility is located on Gran Canaria, Spain. The original SWRO system was installed in 1987 and has since been expanded. Description of Conventional SWRO Plant The raw seawater is delivered via an offshore, open, submerged intake. The seawater is filtered though two sets of vertical media filters containing anthracite and sand. The filtered seawater then passes though two sets of cartridge filters sized at 10 and 5 microns. The conventional SWRO plant at Maspalomas II consisted of five trains. The seawater intake 198
New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
capacity is 41,000 m3/day. The SWRO system recovered 40 % of the seawater as product water, with 60 % of the water being rejected to the sea through a brine water outfall system. The seawater feed contains 35,000 mg/l TDS. The original SWRO plant used Francis Turbines for energy recovery. Pilot Test of Toray Brine Conversion System In the late 1990s, the system needed to expand again. A pilot test of the Toray BCS was undertaken at the site (2). Table 2 compares the actual data from the pilot tests to the targets. Table 2: Pilot Test Data from Maspalomas Feed
1st Stage Permeate
BCS Permeate
Product
350
140
70
210
35, 438
165
173
168
-
40 %
33 %
60 %
350
140
70
210
Water Quality (mg/l)
-
< 350
< 350
< 350
Water Recovery
-
40 %
33 %
60 %
Actual Water Quantity (m3/day) Water Quality (mg/l) Water Recovery Target Water Quantity (m3/day)
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Full-scale Brine Conversion System Based on successful pilot testing of the Brine Conversion System at the SWRO plant, the decision was made to expand the facility using a second stage SWRO system to recover reject from one train of the existing single stage SWRO facility. The advantage of this approach was that the seawater intake and pretreatment systems did not require expansion. This was the first full-scale plant in the world to use the new BCS, and it has been in operation since 1999. In this system, the brine from the conventional SWRO system is pressurized up to 90 bar with booster pumps. The pressurized brine then flows into the brine concentrator membranes, which recover 33 % of the water as product water. A Pelton wheel recovers the residual energy in the reject water. At the time of writing, a BCS has been installed on three of the five SWRO trains. Trains BCS1 and BC3 consists of 28 vessels of 5 elements per vessel. Train BCS4 has 56 vessels of 5 membrane elements per vessel. Table 3 compares the product flow rate, the water recovery, and the product quality of the three BCS units. Figure 1 shows the process flow diagram for one of the trains and Figure 2 illustrates the module rack. Table 3: BCS Trains at Maspalomas II
BCS1
BCS3
BCS4
Product flow (m3/h)
40
44
110
Recovery (%)
26
28
29
Product Quality (mS/cm)
960
920
560
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
Figure 1: Process Flow Diagram for one BCS unit at Maspalomas II
Figure 2: BCS Module Rack at Maspalomas II
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Performance Table 4 shows the water quality of the feed, first stage and BCS permeates and first stage BCS rejects. The BCS is producing permeate of higher quality than the first stage, even though the concentration of feedwater to the BCS is higher than to the first stage. The membranes in the BCS were installed later than the membranes in the first stage, and this is the reason for the better quality from the second stage. Figure 3 plots the feed pressure to the first stage and the BCS versus time. The feed pressure to both stages has been constant during the operation of the plant, at about 68 bar for the first stage and 90 bar for the BCS. Figure 4 plots the first stage and BCS product quality as well as the percent water recovery versus time. Table 4: Water Quality Data RO Feed
1st Stage Permeate
BCS Permeate
1st Stage Reject
BCS Reject
Sodium (mg/l)
11,900
134
106
19,700
31,000
Calcium (mg/l)
432
1.6
0.8
780
1,080
1,407
3.4
2.9
2,549
3,635
430
5.0
4.0
650
1,075
Chloride (mg/l)
21,800
222
170
37,000
55,200
Bicarbonate (mg/l)
115.9
43.7
3.7
190,3
345.3
Sulfate (mg/l)
3,300
9.0
9.0
5,400
7,200
TDS (mg/l)
39,391
379
298
66,282
99,547
6.98
6.14
6.18
7.15
7.37
Magnesium (mg/l) Potassium (mg/l)
Kg/cm2
pH
95.00 90.00 85.00 80.00 75.00 70.00 65.00 60.00 55.00 50.00
BCS Pressure
1º Stage Pressure
days
Figure 3: Feed Pressure versus Time 202
New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
60.0 58.0
700.00 650.00 600.00 550.00 500.00 450.00 400.00
56.0 (%)
uS/cm
850.00 800.00 750.00
54.0 52.0 1º Stage Product Q uality
50.0
B C S Product Q uality
Total recovery
days
Figure 4: Product Quality & Water Recovery versus Time Table 6 compares the single stage SWRO system, the combined SWRO and BCS system, and the projected system with a BCS added to all trains. Since both systems use the same feed flowrate, the intake system did not have to be expanded to achieve more production. Also, the pretreatment system did not have to be expanded, and the amount of chemicals used in the pretreatment system per m3 of product is reduced. The projected maximum water recovery with all SWRO brine feeding a BCS system is 60 % rather than 40 %. The costs of operation of the intake & pretreatment system would be reduced by 33 % per m3 of product. This expansion was possible with no capital investment in seawater intake, pretreatment system or brine outfall system. For a new facility designed with a BCS, there would be capital cost savings of 33 % per m3/day of installed capacity for the pretreatment & discharge systems.
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Table 6: Maspalomas II Flowrates SWRO System
SWRO + BCS System
Projected System
Feed Intake (m3/day)
41,000
41,000
41,000
SWRO Product
16,400
16,400
16,400
SWRO Waste
24,600
12,479
-
BCS Feed
-
12,121
24,600
BCS Product
-
4,000
8,000
Total Product
16,400
20,400
24,600
Total Waste
24,600
20,600
16,400
40 %
49.75%
60%
Water Recovery
Energy Balance For the conventional SWRO train, the production rate is 118 m3/h. The total power consumed by the high pressure pump, minus the power recovered by the Francis turbine, is 445 kW. The total electrical energy consumption of this train is 3.77 kWh/m3. For the trains with BCS units installed, the SWRO product flow is 118 m3/h, and the BCS product flow is 41 m3/h, so the total flow is 159 m3/h. The total power consumed by the high pressure pump and the BCS booster pump, minus the power recovered by the Pelton wheel, is 533 kW. Hence, the total electrical energy consumption of this train is 3.35 kWh/m3. The energy consumption per unit of water produced by the SWRO train with BCS is lower than the energy consumption per unit of water produced by the conventional SWRO train. Concentrate Disposal The average concentration of the reject from Maspalomas II is over 90,000 mS/cm. A study was performed to evaluate the effect on flora and fauna in the area near the discharge (3). This study showed that the discharge from Maspalomas II did not have any effect on flora and fauna near the outfall.
Case Study 2: Kompania di Produkshon di Awa I Elektrisidat Di Korsou KAE, now Aqualectra is the municipal supplier of potable water and electricity for the Caribbean Island of Curaçao, the largest of the five islands of the Netherlands Antilles. Faced with increasing demand for potable water and an aging distillation plant, K.A.E. awarded a contract to the authors’ company to build, own & operate a SWRO facility. The original facility became operational in 1996. The original capacity was 3,000 m3/day. The plant was expanded in 1999 and 2000, and now produces 10,200 m3/day. 204
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Description of System This SWRO system consists of a first stage RO system using conventional SWRO membranes and a second stage BCS to improve water recovery. Pelton wheels are used to recover energy from the SWRO reject. The SWRO permeate is fed to a BWRO system so that the product of the reverse osmosis facility matches the product quality of the thermal desalination units at about 20 mg/l TDS (Total Dissolved Solids). Water Quality Table 1 shows the water quality of the feed, first stage and BCS permeates and first stage and BCS rejects. One might expect that the permeate from the first stage would be lower salinity than the BCS permeate. However, it can be seen that the BCS permeate is actually slightly better than the first stage permeate. This is due to differences in age of the membranes, and shows that the use of the BCS makes no detrimental difference to the product water quality. Table 1: Water Quality Data RO Feed
1st Stage Permeate
BCS Permeate
1st Stage Reject
BCS Reject
2nd Pass Permeate
Sodium (mg/l)
11,741
200
167
18,263
23,074
10
Calcium (mg/l)
466
3.6
1.6
696
937
0.03
1,406
10.4
4.8
2,179
2,800
0.07
460
8.1
7.5
714
936
0.42
20,695
330
272
32,553
41,922
15.2
142
4.9
4.9
221
288
3.66
Sulfate (mg/l)
2,952
19.3
8.4
4,596
6,045
0.13
TDS (mg/l)
37,862
576
466
59,222
107,208
29.48
8.1
6.8
6.6
8.0
7.9
6.5
Magnesium (mg/l) Potassium (mg/l) Chloride (mg/l) Bicarbonate (mg/l)
PH
AQUALECTRA Plant Summary: 10,200 CMD (2,692,800 US GPD) Configuration:
Open seas intake, Feed water Pumps, MMF’s, CF, Positive Displacement HP Pumps, Calder Pelton Wheel Turbines, Conventional 1st pass, BCS Pass, 3 stage second pass, UV disinfection, and product pumping)
Recovery:
40% first pass, 58% overall
Product Quality:
< 40 mg/l
Power:
2.6 kWhr/m3 1st pass / 4.2 kWhr/m3 overall (includes 1st pass, BCS stage, 3 stage 2nd pass, UV disenfection, and product pumping).
Performance:
Some start-up problems, currently over 95% on-line.
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
Case Study 3: Crocus Bay Expansion The Crocus Bay desalination Plant in Anguilla, West Indies is the municipal supplier of potable water and electricity for the Eastern Caribbean Island of Anguilla. Faced with increasing demand for potable water and brackish water wells that were becoming increasingly saline, The Anguillian Government awarded a contract to the authors’ company to build, own & operate a SWRO facility. The original facility became operational in 1999. The original capacity was 60,000 US gallons per day. The plant was expanded in 2000, to produce 90,000 US gallons per day by installing a BCS system on each of the four independently operating SWRO single stage trains. Description of System This SWRO system consists of a first stage RO system using conventional SWRO membranes and a second stage BCS to improve water recovery. Pelton wheels are used to recover energy from the SWRO reject. The SWRO permeate is fed to a BWRO system so that the product of the reverse osmosis facility matches the product quality of the thermal desalination units at about 20 mg/l TDS (Total Dissolved Solids).
Crocus Bay Plant Summary: 3,409 CMD (900,000 US GPD) Configuration:
Open sea intake, Feedwater Pumps, MMF’s, CF, Positive Displacement HP Pumps, Calder Pelton Wheel Turbines, Conventional 1st pass, BCS pass, substantial product pumping.
Recovery:
58%
Product Quality:
< 800 micro-siemens
Power:
2.85 kWhr/m3 1st pass, 4.0 kWhr/m3 overall
Performance:
Over 95% on-line after initial shakeout of plant.
Case Study 4: WEB Bonaire WEB is the municipal supplier of potable water and electricity for the Caribbean Island of Bonaire, part of the Netherlands Antilles. Faced with increasing demand for potable water and an aging distillation plant, WEB Bonaire awarded a contract to the authors’ company to build, own & operate a SWRO facility. The original facility became operational in 1998. The present capacity is 1,633 m3/day.
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
Description of System This SWRO system consists of a first stage RO system using conventional SWRO membranes and a second stage BCS to improve water recovery. A Dyprex work exchanger are used to recover energy from the SWRO reject. A portion of the SWRO permeate is fed to a BWRO system so that the product of the reverse osmosis facility meets the stringent product quality standards of the Bonairian government at about 40 micro siemens.
WEB Boniare Plant Summary: 1633 CMD (431,112 US GPD) Configuration:
Open sea intake, Feed water Pumps, MMF’s, CF, Positive Displacement HP Pumps, DYPREX Work Exchanger, Conventional 1st pass, partial 2nd pass, product pumping.
Recovery:
58% overall
Quality:
< 40 micro-siemens
Power:
2.85 kWhr/m3 overall
Performance:
Over 95% on-line since commissioning
Case Study 5: Handsome Bay, BVI The Ionics plant at Handsome Bay one of several municipal plants, strategically located to supply potable water for the many islands of the British Virgin Islands. The BVI government warded a contract to the authors’ company to build, own & operate a SWRO facility in Handsome Bay in 1993. The present capacity is 568 m3/day (150,000 US GPD). Description of System This SWRO system consists of a first stage RO system using conventional SWRO membranes. A Dyprex work exchanger is used to recover energy from the SWRO reject.
Handsome Bay, BVI Plant Summary: 568 CMD (150,000 US GPD) Configuration:
Open sea intake, Feed water Pumps, MMF’s, CF, Positive Displacement HP Pumps, DYPREX Work Exchanger, Conventional 1st pass.
Recovery:
40% overall
Quality:
< 400 mg/l TDS
Power:
3.00 kWhr/m3 overall
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction” Performance:
Over 95% available on-line since commissioning
3.2 Environmental Advantages When considering seawater desalination processes, an important factor is the potential effect on the environment. Using the Toray brine recovery system does increase the concentration of the brine discharge to the ocean, and at first glance, one might consider this to be a disadvantage of this process. However, when one considers the overall advantages of the process, the environmental benefits of the two-stage process are significant. The size of the seawater intake system is 33 % smaller than a one-stage system, so this system has less of an effect on the environment. Since the pretreatment system is smaller, the chemical consumption and related waste is reduced by 33 %. While the total salt concentration in the brine is higher, the volume of brine is reduced by 50 % over a one-stage plant. Since the volume is lower, the area around the brine discharge point that sees an increased salinity over normal seawater concentrations is much smaller than with a single stage plant. Also, since the electricity consumption is reduced, the amount of CO2 gas exhausted in the electricity generation process is reduced by 10 – 15 %.
OPTIMIZING ENERGY RECOVERY AND BRINE RECOVERY In a single stage SWRO plant, as water recovery increases, energy consumption decreases since less water has to be pressurized to produce the required amount of product water (1). The relationship that higher water recovery will reduce energy is one of the reasons for the development of the BCS. Obviously, since the salinity is higher in the second stage, the pressure required for the BCS is much higher than for the first stage and so, as water recovery increases, the benefit of energy savings decreases. Also, the efficiency of pumps and energy recovery devices working at different operating conditions changes the amount of electrical energy consumed, and the amount of energy that can be recovered. There is also power consumed by the intake, pretreatment and outfall systems and this power is lower with a higher water recovery system. In situations analyzed by the authors’ company, the comparison of power consumption between a lower recovery single stage SWRO design and a higher recovery two stage design varies depending on the feedwater salinity and the type of pumps and energy recovery devices selected. In some cases, the single stage design uses least energy. In other cases, as demonstrated at Maspalomas II, less energy is consumed with a two stage than with a single stage design. There are several ways to combine energy recovery devices with a BCS to minimize the electrical energy required per unit volume of water produced. The right choice for a particular plant will depend on several factors including the size of the plant, the cost of 208
New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
power, the capital cost of various energy recovery devices and the maintenance requirements of the customer. At the Maspalomas II plant, energy is recovered from the BCS brine reject by a Pelton wheel attached to the first stage high pressure pump. A booster pump is used to increase the pressure of the first stage reject to the BCS feed pressure. An alternative way to minimize the overall energy consumption per unit of water produced would be to use a combination of a BCS with a turbocharger. A high pressure pump is used to feed the first stage SWRO system. The reject from the first stage can be boosted to the BCS feed pressure using a turbocharger (4). The turbocharger recovers the energy it uses to boost the first stage reject from the BCS reject. 4. Conclusions Over the last 20 years, innovation in the RO field, such as in the areas of RO membrane design and application, and energy recovery devices has significantly reduced the cost of producing desalinated seawater with RO. In the 21st century, development in these areas and others will continue to improve upon seawater desalination technology, delivering more options and more affordable water for the Caribbean. The BCS is a proven technology for recovering up to 60 % of seawater as product water. The BCS produces water of approximately the same quality as a conventional SWRO plant. Higher water recovery allows existing plants to expand without requiring additional investment in intake and discharge structures, and pretreatment. The electrical energy consumed per unit volume of water produced is approximately the same for a system using a BCS as for a single stage SWRO system, and in some cases is lower for the high recovery system. The combination of BCS and the appropriate energy recovery device can minimize the electrical energy consumption of a plant. As the BCS is applied more widely to full-scale plants it is expected that energy recovery devices will be used in creative ways to reduce power consumption further. Energy Recovery devices need to be evaluated on a case-by-case basis. Turbo chargers, Pelton wheels and work exchangers all have different merits and all produce energy savings with the greatest savings inversely proportional to their relative costs. Work exchangers have proven reliable performance histories and have demonstrated significantly lower energy consumption than other available products. For long-term, larger applications where energy costs are high, although they have higher capitol costs, can be the least expensive overall solution (considering operating and capitol costs).
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New Sea Water Reverse Osmosis Plants for the Caribbean “Energy Recovery, Brine Recovery & Cost Reduction”
5. References 1. 2. 3. 4. 5. 6. 7. 8. 9.
Morris, A. B., “Curaçao, K.. A. E. World Leader in Seawater Desalination Since 1928 Adds Seawater Reverse Osmosis Plant in 1997,” Int’l Desalination & Water Reuse Quarterly. Gruendisch, A., “Re-Engineering of the Pelton Turbine for Seawater & Brackish Water Energy Recovery,” Int’l Desalination & Water Reuse Quarterly, Vol. 9/No. 3, Nov/Dec 1999. Calder bulletin, “Pelton Wheel Energy Recovery Turbines,” PUB. 9008, 1997. Uchiyama, T., M. Oklejas & I. Moch, Jr., “Using a Hydraulic Turbo Charger and Pelton Wheel for Energy Recovery in the same Seawater RO Plant,” Proceedings, IDA World Congress on Desalination and Water Reuse, San Diego, CA, Sept, 1999. Kurihara, M., H. Yamamura & T. Nakanishi, “High Recovery / High Pressure Membranes for Brine Conversion SWRO Process Development and its Performance Data,” Proceedings, Conference on Desalination & Environment, Las Palmas, Canary Islands, Nov, 1999. Toray Industries, Inc., “Brief Introduction of Seawater Desalination Technology,” July, 2000. Moch, I., Jr., “The Case for and Feasibility of Very High Recovery Sea Water Reverse Osmosis Plants”, Proceedings, ADA North American Biennial Conference & Exposition, South Lake Tahoe, NV, August, 2000. Kurihara, M., H. Yamamura & T. Nakanishi, “High Recovery / High Pressure Membranes for Brine Conversion SWRO Process; Development and its Performance Data”, Desalination 125 (1999) 9-15. Talavera, J., J.Quesada Ruiz , “Identification of the mixing processes in brine discharges carried out in Barranco del Toro Beach, south of Gran Canaria”, Desalination 139 (2001) 277-286.
10. Toray, “Brine Conversion 2-stages Seawater Desalination System”, commercial literature.
Authors: Shawn Meyer-Steele, Antonia von Gottberg, Jose Luis Talavera Ionics Incorporated, 2915 Catalina Street, Miami, Fl 33133 tel: (305) 672-2050 fax: (305) 448-7650 E-mail:
[email protected]
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Well-Field Development of the Barbados Water Authority Desalination Plant by Ken Larry Goring, M.Sc., B.Sc., Hydrogeologist, Barbados Water Authority
Abstract The 1993-1996 Barbados Water Resources Management and Water Loss Study funded by the Barbados Government and the Inter-American Development Bank; identified the need for augmentation of the public water supply as a means of satisfying projected domestic consumption increases. These increases were derived from 1996 consumption figures of 485.81 l/s for a population size of 262,215 to 2006 consumption figures of 496.54 l/s for a population of 271,123. As a result of these findings a desalination plant was designed and officially opened in February 2000 to treat brackish water in the Freshwater Bay area of Spring Garden, located on the southwest of the island (see figure 1). The site is 1.1 km from the coast adjoining the Caribbean Sea and lies within the first Pleistocene coral limestone reef terrace of the island. Old beach sediments of medium-coarse poorly sorted sand and gravel with near shore shells and corals are found at varying depths interspersed with both hard impermeable and vuggy coral limestone. The plant combines filter and reverse osmosis (RO) treatment for a capacity output of 6 MGD of freshwater. Ten feed wells situated to the east (inland) of the plant with average water quality between 700-1000ppm total dissolved solids supply the brackish water to the plant (figure 2). The plant operates at 75% efficiency, disposing of the brine into four wells each 41m deep, located 31.5m seaward of the RO plant. Pump tests conducted by the author provided expectedly high transmissivity rates of 7.0 * 102 m2 /day. However from the pump tests a peculiar feature was noted between feed wells number 5 and 6 (see figure 2). Drawdowns in top water levels during the pumping tests were significantly lower in the northern well-field than in the southern well-field. This feature was further investigated and from salinity profiling the brackish to seawater interface was found to be lower in the northern section of the well-field. Chloride results for the year 2000 reveal a pattern of increasing chloride values during the dry season December to May, but a consistently lower value in the northern well-field for the entire year. Additional monitoring boreholes were drilled in the northern well-field, one of which was drilled near feed well number 6. The logging profile revealed a large sand belt and small caverns in the limestone. The sand belt transects the well-field and appears to thicken to the north. The sand section and cavernous limestone provide a path of preferential flow for freshwater seaward to the brackish water aquifer and is most probably the cause of the lower salinity of the feed water in the northern section of the well-field. The significance of these findings is related to the problem of re-circulation of the brine to the feed wells (dye tracer testing) and the need for selection of a new site for the disposal wells. Also the problem of increasing salinities with the dry season possibly worsened by the 2001 drought, and the brine poisoning could see increased pumping from the northern section of the well-field. Presently the plant is not at full production, so the feed wells in operation
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Well-Field Development of the Barbados Water Authority Desalination Plant
are rotated. Based on the above findings a reduction of pumping in the southern well-field and a shift in the disposal wells northward should be considered. The importance of continuous monitoring of desalination plants, thorough hydro-geological studies and there impacts in this case brine re-circulation and saline intrusions affect the development of the well-field and can shorten the life span of the RO membranes. Endangerment of the marine and brackish water environment is impacted by salinity increases and can affect inland freshwater pumping wells. Key Words Unconfined Aquifer – An aquifer in which the upper limit of the zone of saturation is at atmospheric pressure, also referred to as the water-table aquifer. Well-field development – The continuous pumping of single or multiple wells within a designated region until stable conditions of equilibrium of the water table levels are reached and maximum efficiency in pumping is reached. Karstic Limestone – Highly chemically weathered limestone, displaying characteristic solutional features such as caverns, vugs (small cavity) and underground streams. Desalination – Process of removing salts (dissolved solids) from sea or brackish water to make it into potable (drinkable) water. Introduction The Barbados Water Authority (BWA) determined the need for a reliable augment to the freshwater resources. This need was made more apparent following the one in hundred and fifty years drought in 1994-1995. A brackish water desalination plant capable of delivering 30,000 m3/day of potable water for a period of 15 years was determined. A build-ownoperate agreement for water supply was entered between the BWA and Ionics Freshwater Ltd. in conjunction with a local joint venture partner Williams Industries. Ionics Freshwater Ltd. and Williams Industries designed, manufactured, constructed, installed, commissioned and operate the plant, which went in production February 15, 2000. The desalination system utilises reverse osmosis (RO) and filtration. Pumped brackish water is pre-treated by cartridge filters for removal of suspended solids and particulates down to a size of 5 microns. Ultra-low pressure brackish water RO membranes separate the desalted stream from the concentrated waste. Presently up to 75% of the pressurised feed water is returned as freshwater. Post treatment includes the addition of lime for taste and chlorination. The ten feed water wells were each augered to a depth of 22.9m or 75ft at a diameter of 1.5m. The wells were cased with 24 inch PVC solid casing from surface to 15.24m (50ft). Below the casing are 24inch stainless steel screen with slot size openings of 0.04 inches. The screens extend from 50ft to 70ft (21.3m). A five-foot solid PVC casing caps the bottom of the screens. Gravel packing of the annulus with 2.38mm (granule) to 1.68mm (very coarse sand) aided with the control of sand. 1.5MGD (5,677 m3/day) spindle pumps are installed in the wells. 212
Well-Field Development of the Barbados Water Authority Desalination Plant
Four disposal wells drilled first to 15inches in diameter to depths of 10 to 45ft and then to 12inches to depths ranging from 160ft-200ft. The first PVC solid 14inch casing was installed in the upper section of the hole drilled with the 15inch bit. This casing held back and cased the sand belt, which often caved. The second casing set was 10inch solid PVC and was set from surface to 130ft. Monitoring boreholes 2 inches in diameter were drilled to depths varying from 170ft to 195ft. Figure 2 displays the locations of the feed water wells, monitoring boreholes and disposal wells of the desalination plant. Methods Pump Tests Pump tests were conducted to determine the safe yield of the aquifer and hydraulic conductivity and transmissivity of the aquifer material. The first pump test was conducted May 1999 by the author, and utilised two feed wells (pumping at maximum capacity) and four piezometers (monitoring boreholes). The pumps were started simultaneously and drawdowns recorded until static equilibrium of the aquifer was achieved, that is until no further drop in the top water levels was recorded. Salinity profiles prior to test pumping and afterwards were obtained using a SEBA KLX, probe with temperature, ph and salinity parameters. The analysis of the pump test data was performed using the Theis model for unconfined aquifers. Subsequent pump tests were performed using four and then six feed wells, pumping also at the maximum capacity were conducted in order to further determine the safe yield of the aquifer when pumping over the entire well-field (Mwansa & Ifill, 2000). Dye Tests The dye tracer tests (Mwansa &. Ifill, 2000) were conducted in 2000. Background measurements from the feed-well number 3 and disposal well number 3 were taken. This was in order to determine the background levels of the dye used. The dye used was Rhodemine. Dye was injected into the disposal well and a charcoal pack placed at the feed well. Salinity Profiles Salinity profiles were conducted on monitoring boreholes number 3, 4 and 5 at specific times throughout the year. Times selected for measurement were during the wet (June – November) and the dry season. In addition the effect of tides was investigated, measurements taken coinciding with high and low tides. Drilling Logs Drilling logs were obtained from the drilling of the feed wells and disposal wells. Recordings of drill cuttings were examined visually and described. Observations of rates of penetration and instances of loss circulation of drilling fluid were noted.
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Well-Field Development of the Barbados Water Authority Desalination Plant
Results Pump Test Analysis of the Spring Garden Aquifer Q = 2pKD (Smw - Sm) ln (r1/rw)
=>
KD = Q x ln (r1/rw) 2p (Smw-Sm)
KD = 7200 m3/day. ln (87.5m / 0.61m) 2p (0.772m - 0.005m) Transmissivity of the aquifer KD = 7,419.2 m2/day or 5.97 x 105 U.S gal/day. Ft Comparison: Tidal - (Stanley Report, 1976) = 1.4 m2/s = 20,960 m2/day Applewhaites (WRM&WLS, 1996) = 0.017 m2/s = 1,468 m2/day Buttals (WRM&WLS, 1995) = 0.004 m2/s = 345.6 m2/day The Transmissivity calculated is not as high as the tidal value from the Stanley Report but the value is higher than Transmissivities of Applewhaites and Buttals that are inland. This is expected considering the aquifer at Spring Garden comprises beach, gravel and coral limestone as opposed to Amphestegina and fore-reef coral Limestone found further inland. Hydraulic conductivity K = T/D = 196.07m/day K = 2.27 x 10-2 m/s Falls in the range of values of hydraulic conductivity as Gravel. N.B. Tidal fluctuations are negligible · Measurements are approximate. Tidal Observations Salinity Interface Salinity profiles were taken in BH #3, 99-05-22 in the morning during the high tide. The interface was determined to be at 45m. The profile was repeated in the same borehole, 99-05-27 in the evening during the low tide and the interface determined to be at 46m. The movement of the interface of 1m is considered due to tidal fluctuations. Salinity Profiles The following plots of salinity profiles are salinity mS/cm versus depth/m.
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Well-Field Development of the Barbados Water Authority Desalination Plant
Desalination Well Field, Spring Garden Average Conductivities (2000 - Wet Season) 1800
1600
1200
1000 Average (Feed Wells 6 - 10) Average (Feed Wells 1 - 5)
800
600
400
200
9/ 6/ 00 9/ 13 /0 0 9/ 20 /0 0 9/ 27 /0 0 10 /4 /0 0 10 /1 1/ 00
8/ 9/ 00 8/ 16 /0 0 8/ 23 /0 0 8/ 30 /0 0
8/ 2/ 00
7/ 5/ 00 7/ 12 /0 0 7/ 19 /0 0 7/ 26 /0 0
6/ 7/ 00 6/ 14 /0 0 6/ 21 /0 0 6/ 28 /0 0
0
Date
Desalination Plant, Spring G arden Feed W ell Conductivities (2000 - Dry Season) 1600
1400
1200
1000
Average (Feed W ells 6 - 10)
800
Average (Feed W ells 1 - 5) 600
400
200
Date
215
5/ 24 /0 0
5/ 17 /0 0
5/ 10 /0 0
5/ 3/ 00
4/ 26 /0 0
4/ 19 /0 0
4/ 12 /0 0
4/ 5/ 00
3/ 29 /0 0
3/ 22 /0 0
3/ 15 /0 0
3/ 8/ 00
3/ 1/ 00
0 2/ 23 /0 0
Conductivity (mS/cm)
Well Conductivity (mS/cm)
1400
Well-Field Development of the Barbados Water Authority Desalination Plant
Linear Trend in Conductivity at Spring Garden 1700
1600
1500
Conductivity
1400
1300
Avg Conduct Linear (Avg Conduct)
1200
1100 1000
900
4/ 25 /0 1
2/ 25 /0 0 3/ 25 /0 0 4/ 25 /0 0 5/ 25 /0 0 6/ 25 /0 0 7/ 25 /0 0 8/ 25 /0 0 9/ 25 /0 0 10 /2 5/ 00 11 /2 5/ 00 12 /2 5/ 00 1/ 25 /0 1 2/ 25 /0 1 3/ 25 /0 1
800
Date
Discussion The drilling logs and drilling records confirm that the well-field is heterogeneous in lithology. The beach deposits and limestone cap rock vary in thickness and depth across the well-field. The sand belt, which posed problems while drilling because of its collapsibility, was encountered in all of the wells in the well-field but varied in thickness. The sand belt encountered in the latest borehole number 5, drilled in the northern section of the well-field was less than 5m, while in disposal well number 1 in the southern end of the field, the thickness was approximately 15m. Loss of circulation while drilling occurred within the upper 15m of borehole 5 but was some 5m lower in disposal well number 1. Hence suspicions of the variability of lithologies were confirmed. In addition, more cavities/caverns are possibly located in the northern well-field and specifically between feed well number 5 and 6. Salinities of the feed water wells show increases over the entire well-field during the dry season. This is as expected considering that freshwater recharge is decreased and the rise in salinity interface (Ghyzen-Herzberg equation) provides the balance in equilibrium of these two bodies of water. However salinities of the northern feed wells were consistently lower than the southern well-fields, during both the wet and dry seasons. In addition, the salinity interfaces were also higher in the southern well-field.
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Well-Field Development of the Barbados Water Authority Desalination Plant
These observations indicate a preferential flow path of freshwater in the northern well-field. Thus greater recharge in the northern section and lower salinity interfaces and salinities of feed water. The dye tracer tests indicate that reverse circulation is occurring (Mwansa & Ifill 2000). Dyes injected in the disposal wells were detected in feed water wells 2 and 3. In addition the dyes were also detected in the West Indian Refinery well and dyes injected into the Barbados Light and Power Ltd wells to the northwest of the well-field (see fig.2) were detected in feed well number 8. Conclusions
·
The northern section of the well-field that is feed wells 6-10 should be utilised more. Present production is at 3.5 MGD or half of the capacity of the plant, due to difficulties in the hydraulic piping and reservoir network in accommodating water quantities above this limit. The feed wells are rotated, with any 5 in production at any point in time. It is recommended that the northern well-field should be pumped exclusively until the hydraulic network is ready to accept the maximum output from the plant, which would require all of the feed wells.
·
The Barbados Water Authority should consider acquiring the adjacent property to the north of the well-field.
·
Plans to relocate the disposal wells further west possibly utilising the Barbados Light & Power cooling wells should be pursued urgently.
·
Additional boreholes should be drilled closer to the shoreline in order to determine the sphere of influence of the pumping wells at maximum capacity.
·
A computer model should be designed for the entire well-field and surrounding area (MODFLOW suggested). This should include the West Indian Refinery Well and Barbados Light and Power Ltd Wells. Preliminary groundwater contouring indicate that mounding is occurring around the re-injection wells of the two previously mentioned companies and a reverse gradient maybe established over time due to pumping from the feed wells. The model simulations could better predict the flow paths of the brine and any threats of re-circulation. In addition the effects of long term pumping on the movement of the salinity interface could be simulated and effects on nearby inland public pumping freshwater wells considered.
·
From these model simulations and continued observations, the Barbados Water Authority could determine what proportion of the desalination plant output could be left as reserve capacity and what decreases/increases in pumping from the public wells could be considered in average, drought or wet years.
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Well-Field Development of the Barbados Water Authority Desalination Plant
·
Above all, measurements of chloride levels in all of the feed wells, and salinity profiling of all monitoring wells (weekly) should be continued.
References Goring, Ken L., July 2 1999, Pump Test Report Of The Desalination Plant, Spring Garden. Dr. Mwansa, John & Ifill, Alex., June 1 2000, Hydrogeological Investigations For The BWA Brackish Water Reverse Osmosis Plant Well-field, At Spring Garden, St. Michael. Final Report On Task3, Water Resources Management and Water Loss Study, June 1998 Author: Ken Larry Goring, M.Sc., B.Sc., Hydrogeologist, Barbados Water Authority. Tel: (246) 425-9110 Fax: (246) 425-9121 E-mail:
[email protected]
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Well-Field Development of the Barbados Water Authority Desalination Plant
Attachments
Figure 2
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Coatings and Linings Providing Corrosion Protection and Structural Rehabilitation in the Wastewater Industry by Joanne B. Hughes Abstract This paper will provide guidance to contractors, specifiers and end users in the municipal wastewater industry on the proper use of protective and structural coating systems in sewer rehabilitation. A multitude of coating and structural systems are available in the underground rehabilitation market today. The versatility of these systems enables their cost-effective use in many structures within collections systems requiring rehabilitation. These systems, when properly designed and applied, provide corrosion protection and structural loading resistance as a composite structure with host materials. These systems are commonly used in manholes, lift and pump stations, large diameter pipelines, junction boxes, siphons, outfalls and points of convergence and transition. Contractors, large and small, are adding coating technology to their line of services to compliment existing technologies including cured-in-place pipe, fold and form, TV, cleaning and dig services. Capabilities, limitations, minimum performance, contractor training, application technique and inspection will be presented in both technical and case history formats. Updates will be provided on industry standards, references and testing available through various resources. Key Words: Coatings Protective Structural Corrosion Rehabilitation Introduction Assessment of existing sanitary sewer systems, as well as new construction of treatment facilities and expansion of collection systems, requires a long-term plan be implemented to address the ever increasing corrosivity to which virtually every structure is exposed. Coating systems have evolved that successfully achieve rehabilitation programs goals including elimination of infiltration, protection against microbiologically induced corrosion and potential exposure to industrial waste, restoration of structural integrity lost from age, erosion and poor construction.
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Coatings and Linings Providing Corrosion Protection and Structural Rehabilitation in the Wastewater Industry
Types, Purposes & Uses Coating and lining systems for the sewer rehabilitation market vary greatly. Systems include thermoplastic sheet liners, formed and spray-applied cementitious materials and various types of polymers. Thermoplastic sheet liners range from those utilizing formed-in-place cement as a base to others utilizing polyurethane foams and mastics to secure the plastic panels to the host structure. Cementitious variations include Portland-based cements and to pure-fused calcium aluminates and formulations enhanced with antimicrobial additives. Polymers incorporate rigid and elastomeric variations of polyurethanes, polyureas and epoxies. Each system has distinct advantages and disadvantages that can be evaluated and matched with specific project restrictions and needs. Most importantly, all of these systems require application by qualified, well-trained contractors. The versatility of these systems enables cost-effective use on concrete, masonry and metal structures requiring rehabilitation. These systems are commonly used in manholes, lift and pump stations, large diameter pipelines, junction boxes, siphons, outfalls and points of convergence and transition, clarifiers, digestors, biofilters, floculation basins, tanks, filter basins, distribution pipelines, etc. Limitations Proper adhesion, monolithic installation and appropriate long-term strengths are the most critical elements to effective long-term performance of any coating or lining system. All systems have limitations to be considered before selecting a technology. Adhesion – A verifiably acceptable mechanical bond to the host structure is essential to long-term performance, and is directly related to 1) surface preparation and 2) formulation of a surface and moisture tolerant lining system. Proper surface preparation of a host structure requires that the contractor removes all contaminants including oils, greases, laitance, existing coatings, etc. from the surfaces to be coated. A sound, clean substrate with adequate profile and porosity to promote adhesion between the host structure and the coating or lining system being installed must be produced. Generally, this can be accomplished with proper decontamination and cleaning of the surfaces using environmentally friendly degreasers, detergents, steam, acid etching, low-high pressure water cleaning1, wet abrasive blast and/or dry abrasive blast. The method chosen for surface preparation is best determined on-site by the contractor who is required to produce a clean, sound substrate per the performance specification. Further examination and understanding of available surface preparation methods is available through National Association of Corrosion Engineers (www.nace.org) and the Society of Protective Coatings (www.sspc.org). Moisture tolerance of a coating or lining system is necessary for underground infrastructure rehabilitation due to the presence of ground water and high humidity. Moisture tolerance varies greatly depending upon the classification of the material. Most cementitious products 1
NACE No. 5/SSPC-SP 12 2000, National Association of Corrosion Engineers, Houston.
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Coatings and Linings Providing Corrosion Protection and Structural Rehabilitation in the Wastewater Industry
are naturally moisture tolerant since they are actually moisture dependent. Polymer mastics used for thermoplastic sheet linings also require installer expertise to allow these products to be successfully installed on moisture filled concrete and masonry substrates. Urethanes contain isocyanates, which are inherently moisture sensitive, typically requiring a moisturetolerant primer such as an epoxy for improved adhesion. Alternatively, in cylindrical structures, rigid urethanes may be applied at greater “stand alone” thicknesses, removing the absolute necessity of a bond to the host material through structural performance of the thicker material. Generally speaking, concrete experts acknowledge epoxies exhibit superior bonding to below grade substrates. Monolithic – A barrier without fault. All coatings and structural systems should be specified to form a monolithic barrier to provide effective long-term elimination of infiltration and corrosion protection. Naturally, cementitious materials remain the most porous or permeable of all coating and structural systems. However, some of these cementitious products, as well as most polymer systems, are used to provide corrosion protection of the host material. Shrinkage and stress cracking are the most prevalent problems with cementitious products, usually induced from improper cement to water ratio or finishing. Stress cracking permits both infiltration and corrosion to continue at an accelerated rate. Polymer systems can be prone to two problems, pinholing and bonding with existing materials. Pinholing is a natural phenomenon simply based on the outgassing of the moisture or air in the host concrete structure and can be controlled and repaired prior to returning a structure to service. Vacuum testing of cylindrical structures can verify integrity of installed systems. Many urethanes have rapid set times (< 60 seconds) and experience less pinholing than epoxies whose set times range from 30 minutes to eight hours. However, the benefit of less pinholing with urethanes is frequently offset due to the lack of adhesion since the coating material has little or no time to penetrate the host material, thermal shrinkage and urethane’s inherent moisture sensitivity. Pinholing with polymer systems can be reduced with penetrating primers, coating surfaces as the surface temperature reduces instead of rising and not coating when the structure is subject to direct sunlight. Thermoplastic sheet lining systems require a skilled heat fusion bonding process for all panel seams in order to form a monolithic barrier. Reinforced cured-in-place systems require a liquid polymer to seal adjoining materials (pipe liners, steps, thermoplastic liners, etc.). Spark testing (holiday detection) is commonly used to inspect polymer and thermoplastic systems to detect pinholes, thin areas and improperly welded seams. Summarizing, specify verifiable monolithic systems. Long Term Strengths – most of the structural polymer liners exhibit physical properties far greater than the strongest concretes. Although a standard method has not yet been accepted for the examination of polymers used in underground construction, it is logical to extend the use of those standards previously accepted for cured-in-place pipeline systems. Several minor deviations are required to acknowledge the fact that some of these structural systems are not reinforced with a continuous layer of fabric. A modified Timoshenko equation and ASTM F1216 have gained some acceptance as a method for determining necessary thickness of spray-applied polymers for structural rehabilitation of underground pipeline systems. There has been similar acceptance of equations used for vertical cylindrical structures (ie. manholes, wet wells, drop shafts, etc.) originating from the ASME Pressure Vessel Code 1952. Additionally, long-term testing of physical properties of spray-applied polymers
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includes ASTM D638 and D790, extended to include immersion in various reagents over time and repeated deterioration of these properties (Greenbook) should be considered. Design Considerations Various design theories and guides have been used to determine necessary thickness and minimum physical properties of polymers used for non-structural and structural rehabilitation. Prevalent thickness recommendations can be summarized as follows: Product Cementitious Thermoplastic liners
Non-Structural 3/8” – 1/2” > 40 mils
Polymers
40 – 80 mils
Structural 5/8” – 4” requires >1” cementitious basecoat 100 – 500 mils
Corrosion Resistant poor – fair (pH >2) good-excellent good-excellent
Independent testing, material evaluations and comparison to other similar materials and methods continues to improve knowledge and performance. Several universities and organizations are working in conjunction with polymer manufacturers to provide independent analyses of those polymers used for structural rehabilitation in underground rehabilitation. These studies should provide the substantiation for an equation that can be used to determine necessary thickness of polymers providing structural enhancement to an existing deteriorated underground structure. Conclusions Cementitious products have been used in underground rehabilitation for centuries. The use of thermoplastic sheet liners, cured-in-place liners and spray-applied polymers began over 50 years ago. However, only in the past 15 years, has there been a significant increase in the specification and use of those products exhibiting greater chemical resistance and longer life expectancy. This can be attributed to accelerated corrosion problems in today’s infrastructure, as well as a greater awareness of corrosion issues. The evolution of the following three crucial components combined as a system permit these systems to last longer and achieve greater success in these difficult environments: · · ·
improved formulation capabilities state-of-the-art installation equipment technology verifiable training and certification programs for contractors
The examination of past and present case studies provide insight into the world of underground infrastructure rehabilitation and structural rebuild and demonstrate increased life expectancy through cost effective installation of coatings and linings.
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References: Joint Surface Preparation Standard NACE No. 5/SSPC-SP 12, Surface Preparation and Cleaning of Steel and Other Hard Materials by High- and Ultrahigh-Pressure Water Jetting Prior to Recoating 2000, National Association of Corrosion Engineers, Houston. Practice F1216-98 Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube 2001, American Society for Testing and Materials, West Conshohocken, PA. Test Method D790-00 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials 2001, American Society for Testing and Materials, West Conshohocken, PA. Test Method D638-00 Standard Test Method for Tensile Properties of Plastics 2001, American Society for Testing and Materials, West Conshohocken, PA. Munger, C.G. 1984, Corrosion Prevention by Protective Coatings, National Association of Corrosion Engineers, Houston. Joint Cooperative Committee of the Southern California Chapter American Public Works Association and Southern California Districts Associated General Contractors of California, “Greenbook” Standard Specifications for Public Works Construction 1994, Building News, Los Angeles. Author: Joanne B. Hughes, Vice President, Raven Lining Systems, 1024 N. Lansing Ave., Tulsa, OK 74106 Tel: (918) 584 2810 Fax: (918) 582 4311 E-mail:
[email protected]
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Re-use of Treated Sewage in Canada for Irrigation & Toilet Flushing by E. Craig Jowett, Ph.D., P.Eng. President, Waterloo Biofilter Systems Inc. Abstract Re-use of highly treated sewage is a positive step in managing water supplies, and can be either “indirect” (i.e., buffered by time and space), or in increasing cases, “immediate” re-use directly after treatment. Immediate re-use of treated sewage in the household occurs in Canadian Arctic communities where water supply is expensive, but also in Vancouver where treatment plants are at capacity. More commonly, treated sewage is re-used for irrigation on golf courses after passing through irrigation ponds. Third-party testing of the standard WATERLOO BIOFILTER® trickle filter system over the past 10 years has shown a consistent average 99% E. coli removal rate (>250 samples at 12 sites), and even >99.9% E. coli removal (swimming water quality) when a 1-m3 up-flow aggregate filter is used after the BIOFILTER. About 95-98% of BOD, TSS and ammonium are removed to make subsurface disposal easy and safe, compared to untreated septic tank effluent. Surface discharge of BIOFILTER effluent from 30 restaurants to the Han River in Korea, without disinfection, is possible because BOD and TSS are consistently 5-6 mg/L. The BIOFILTER effluent is re-used downstream as a potable water source for Yangpyung Province and Seoul. In Canada, when BIOFILTER effluent is further disinfected with sand filters and ozone, the water is effectively potable (except for nitrate) with E. coli values of ~1 CFU/100mL, and is re-used immediately in households for toilets, and sometimes laundry, baths and showers. These re-use sites are located in Toronto (2), the Canadian Arctic (10), Vancouver (20), and northern Ontario (1), under federal government auspices, with more planned for houses and in highway truck stops. In Ontario, large golf courses & resorts with high-strength flows of 30–120m3/d are treated by septic tanks with alum addition for phosphorus removal, a WATERLOO BIOFILTER, re-circulation to remove ammonium, and ultraviolet disinfection. The consistent BIOFILTER effluent (<5 mg/L cBOD & TSS; <1 mg/L NH3-N; <1 mg/L TP; and ~1 CFU/100mL E.coli) could be discharged to high-quality streams, but instead is re-used onsite for irrigation. Professional operation and remote monitoring are key requirements for reuse applications. Our work on landfill leachate with on-site disposal, and some sewage results, shows that 98% of hydrocarbons and VOCs, and 50-95% of heavy metals are removed in the BIOFILTER, thereby reducing contamination of soil and groundwater. After showing consistent treatment over many years with different wastewaters, our experience is that any initial reluctance by golf resort staff, regulator, or homeowner to immediate re-use is overcome and accepted after seeing the installations. Keywords: sewage treatment, residential, restaurants, toilet re-use, resorts, nutrient removal
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Re-use of Treated Sewage in Canada for Irrigation & Toilet Flushing
Water Re-Use Parameters For swimming and bathing, re-used water should be aesthetically pleasing, and with no objectionable colour, odour, taste, or turbidity, and have a pH of 6.5–8.5 due to eye irritation (summarized in Jowett 1997; 2000). The use of the water should also not cause disease caused by pathogenic bacteria, fungi, protozoa, worms, or viruses (e.g., Yates 1994). Pathogen indicators of fecal coliform and total coliform limits for bathing are typically 100 and 1000 CFU/100 mL, respectively. The US EPA (1992) Guidelines for Water Reuse summarize criteria for re-claimed water treatment, in general to the highest degree, with preferred averages for BOD and TSS of <5 mg/L so that disinfection is effective, but always <30 mg/L. Generally non-detectable to 200 CFU/100 mL coliform is required for reclaimed water, and maximum turbidity of 2–5 NTU are recommended. Swimming Quality Water From Sewage With No Active Disinfection The City of North Bay, Ontario, draws its potable water from a lake with no treatment except for screening and chlorination. Algae growth due to phosphorus from septic systems is minimized by keeping new septic systems 30m from the lake, and by a phosphorus removal program on lakefront homes initiated by the City. On one residential site, an above-ground WATERLOO BIOFILTER (Fig. 1a) is followed by a reactive-medium upflow filter to remove phosphorus (Hutchinson and Jowett 1997). The system consists of a septic tank with an effluent filter emptying to a small pump chamber which doses the above-ground BIOFILTER by demand in 20-L doses. Half the effluent returns by gravity to the septic tank, and the other half goes to the upflow filter containing 1 m3 of iron-rich medium (not shown in Fig. 1a), and then to a small leaching bed. (The BIOFILTER can be installed above (Fig. 1a) or below ground (Fig. 1b) and the process is detailed in Jowett and McMaster (1995), and in Jowett and Rogers (2001) in this volume.) Table 1 shows the system performance with an initial 6 months using red sandy soil in the upflow filter, and the last 12 months using expanded clay aggregate (FILTRALITE). BOD and TSS (<5/5 mg/L) are excellent (Table 1) with the resulting water being colourless and odourless. Total nitrogen values of ~20 mg/L represent an average ~50% removal, typical of results reported by Converse (1999).
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Table 1. North Bay domestic sewage analyses after WATERLOO BIOFILTER® and upflow filter treatment 1998-1999; n = number of samples; ‘OUT’ = arithmetic average Parameter Jan 98 – Jun 98 Jul 98 – Aug 99 red soil in upflow ‘Filtralite’ in upflow mg/L n OUT % removal n OUT % removal c+nBOD5 6 <5 ~95 7 ~5 ~95 TSS 6 <2 >94 7 <5 >94 TN 6 19 ~50 7 20 ~50 E.coli CFU/100 mL 4 660 >99 18 <29 99.98 An astonishing aspect of this trial, and one important to wastewater re-use, is the excellent removal of E.coli in the upflow filter. Even within the first six months, the effluent had <1000 CFU/100 mL, and steadily dropped to <75 in the next six months then to <16 in the last six months, approaching what ozone and ultraviolet disinfection achieve. These and other results increase the level of confidence in the use of this treatment train for lower level reuses such as toilet flushing or garden use, without the need for a high-maintenance disinfection system. Buzzard’s Bay Facility—Consistency Of Triplicate Tests The Buzzard’s Bay test facility in Massachusetts (US-EPA and New England Interstate group funded) tests treatment systems in triplicate over a prolonged 2-year period, winter and summer, using non-comminuted sewage and applying household-type diurnal flows. (This compares well with the NSF International Standard 40 test of only 6 months duration using comminuted sewage without winter testing required. However, the new Environmental Testing Verification (ETV) program, sponsored by NSF and US-EPA, has a 12-month test period.) Three WATERLOO BIOFILTERS have been tested here since June 1999 (Table 2). The design is similar to Fig. 1a with 50% of the effluent draining back to the septic tank for denitrification. During the first two months, the BIOFILTER effluent had c+nBOD median values of ~15 mg/L, and thereafter 7.7 mg/L median c+nBOD for overall reduction of 96% (Table 2). (The 50-percentile median better represents the ‘average’ of a skewed population which lie close to zero, but which cannot go below zero (Converse 1999).) Similarly, TSS, ammonium, and fecal coliform removals were very high (98–99%). The total nitrogen value of 13.8 mg/L represents a 60% removal rate.
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Re-use of Treated Sewage in Canada for Irrigation & Toilet Flushing
Table 2. Buzzard’s Bay sewage analyses after WATERLOO BIOFILTER® treatment (triplicate systems) August 1999 – February 2001, after 7 week start-up; n = number of samples; ‘OUT’ = median 50 percentile Parameter Waterloo Biofilter Effluent mg/L n OUT % removal OUT Range c+nBOD5 59 7.7 95.8 2–15 (1 at 32) TSS 52 2.8 97.9 0–13 (1 at 30) NH4-N 111 0.5 98.1 0–3.9 TN 109 13.8 60.0 10–21 Fecal Coliform 106 22,500 99* 4–750,000 cfu/100 mL 99.5 * median removal rate is 99%; geometric mean rate is 99.5% These long-term tests in triplicate show the consistency of treatment and the clarity of effluent which lends itself to improved UV or upflow filter disinfection, or even direct use for toilets and irrigation without disinfection. Effectiveness of soil treatment was also measured, using pan lysimeters, and it was found that 150 cm of sandy soil treats septic tank effluent to the same high degree as the BIOFILTER plus 30 cm of soil (Table 3). Geometric mean removal rates of fecal coliform in the BIOFILTER itself is 99.95% and is a total of 99.99% when the 30 cm of soil is included. Soil treatment does not remove nitrogen. Table 3. Buzzard’s Bay median values of WATERLOO BIOFILTER® effluent plus shallow soil treatment (triplicate systems) August 1999 – February 2001, compared to conventional septic system with deep soil treatment May 1999 – January 2001. Effluent Site c+nBOD TSS NH4-N TN Fecal Coliform BIOFILTER effluent 7.7 2.8 0.5 13.8 22,500* BIOFILTER + 0.3 m soil 4.0 2.0 0.0 11.5 300* BIOFILTER + 0.6 m soil 4.0 1.0 0.0 10.8 550 Septic tank + 1.5 m soil 4.0 1.0 0.0 24.2 5 *geometric mean = 14,800 after BIOFILTER (99.5% removal) and 235 after 0.3 m soil (99.99% removal)
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Re-use of Treated Sewage in Canada for Irrigation & Toilet Flushing
Clublink Golf Resorts—Irrigation Re-Use Or Sensitive Surface Discharge The sewage treatment systems at CLUBLINK’S premium golf course resorts are lowmaintenance WATERLOO BIOFILTER systems which are similar to the above designs but scaled up to design flows of 30–120 m3/d, and 5-day ‘tournament’ peaks of 40-140 m3/d. To meet rigid effluent criteria for ammonium and phosphorus, the system also includes aluminum sulphate addition in the septic tank for phosphorus removal, recirculation for low ammonium discharge, and ultraviolet disinfection for pathogen removal. The effluent is discharged directly to the irrigation ponds and re-used on the golf courses. Effluent from residential homes and resorts are treated together with the stronger clubhouse wastewater, adding additional irrigation water which would otherwise be wasted. These designs are detailed in Jowett and Rogers (2001) in this publication. Korean Restaurant Systems—Direct Discharge To Potable Water Supply The Province of Yangpyung ,northeast of Seoul, Korea, contains the headwaters of the Han River, a major source of drinking water for the City of Seoul (12 million population). An energetic program to clean up sewage wastewater was started by the Province in 1999 with 5 treatment technologies chosen to compete for approval and use in the region. WATERLOO BIOFILTERS were installed at 30 restaurants in SeoJong Town by Batu EnviroTek, using 16m3 capacity septic tanks with ZABEL effluent filters, 7m3 capacity pump tanks, with pumps time-dosing the BIOFILTERS in frequent small doses. The design flows range between 6 and 16 m3/d based on 60L/m2 floor space, but actual flows can be much higher or lower than the design flows. The measured BOD of the mixture of BIOFILTER treated effluent (<10 mg/L) and septic tank effluent ranges from 45 to 568 mg/L, reflecting the typical highstrength wastewater of restaurants. The Province sampled 24 restaurants (6 were closed during the winter) each month and the results to date are depicted in Table 4 for the period of March – June 2000. The effluent quality with this design is very good with the median BOD and TSS values ranging from 2.2 to 6.2 mg/L for an overall median of 5.2 mg/L BOD and 5.3 mg/L TSS. High quality effluent can be predicted when a peak design mass loading of 0.3 kg BOD/m3 foam/day is used for these restaurants. Similar to the CLUBLINK golf resorts, effluent quality is consistent during both busy and slack business days.
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Table 4. WATERLOO BIOFILTER® effluent analyses from 24 restaurants, SeoJong Town, Yangpyung Province, Korea March 2000 – June 2000. Median 50 percentile values of 24 sample sites each month. Parameter March 23 April 15 May 15 May 26 June 19 Overall mg/L c+nBOD5 2.2 4.8 6.2 5.0 4.2 5.2 (1–21) TSS 4.5 3.0 3.0 4.5 3.3 5.3 (1–17) The treated effluent is gravity fed to the Han River without disinfection to be re-used downstream for the local potable water supply. The output consistency is due to having adequate retention time, effluent filters, surge storage and recirculation, with the BIOFILTER being the key component in the treatment process. Only consistency like this provides the regulator with confidence enough to allow direct discharge to a potable water supply. As a result of this, the WATERLOO BIOFILTER has been chosen to treat 14 sites for the Korean Army on flows of 10 to 150 m3/d. ‘HEALTHY HOUSE’ System—Immediate High-Level Re-Use In The House Even more confidence is required by the regulator to allow for immediate re-use of treated wastewater in a house, even for low-level uses such as toilets, but especially for high-level uses such as laundry, baths and showers. Other papers on the Toronto ‘HEALTHY HOUSES’ have been written (Townshend et al. 1997), and this design funded by the federal government agency Canada Mortgage & Housing Corporation (CMHC) is now well known because of immediate re-use in the houses for toilets and laundry, even baths and showers since 1996. Analyses of the final effluent are generally below 5 mg/L BOD and 2 NTU turbidity, however, one could easily see this by looking in the toilet bowl or taking a shower, which is of course, the real test. Approval was initially difficult because the septic system was inside the house, and the immediate re-use aspect was an additional obstacle. The system is continuing its success and is now used in the Canadian Arctic where water supply is difficult and expensive. In the City of Vancouver, a 20-unit condominium CMHC project uses ozonated BIOFILTER effluent directly for toilet flushing. The site attracts attention because of its positive impact on the City’s sewage treatment plants. ‘ECO-NOMAD’ Container System—Immediate Low-Level Re-Use In The House A novel application in housing is the ECONOMAD system which places all utilities, including generator, water supply, heating, and wastewater treatment in a shipping container. The container is sent to site, typically remote locations, and the housing structure is built around it. This is another CMHC project and uses BIOFILTER effluent directly for toilet flushing without sand filters or disinfection.
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Conclusions The WATERLOO absorbent trickle filter is treating residential, restaurant, and commercial golf resort wastewater effectively for re-use of the treated wastewater as a resource rather than a waste product. Pretreatment steps with septic tank digestion, in some cases with alum addition, and post-treatment steps with disinfection by upflow filtration, ozone, or ultraviolet light are means of improving the aesthetic quality to overcome suspicion by the end user. Depending on the type of wastewater and the end use of the treated wastewater, more or fewer components can be added to the system for additional treatment. References Converse, J. C. (1999) Nitrogen as it relates to on-site wastewater treatment with emphasis on pretreatment removal and profiles beneath dispersal units. In: Proceedings, Northwest On-Site Wastewater Treatment, University of Washington, Seattle, R. W. Seabloom, (Ed.), pp. 171–184. Crites, R. and G. Tchobanoglous (1998) Small and Decentralized Wastewater Management Systems. McGraw-Hill, 1084 pp. Hutchinson, N. J. and E. C. Jowett (1997) Nutrient abatement in domestic septic systems: research initiatives of the Ontario Ministry of Environment. In: Septic Odour, Commercial Wastewater and Phosphorus Removal, E. C. Jowett, (Ed.), University of Waterloo, pp. 81– 102. Jowett, E. C. (1997) Sewage and leachate wastewater treatment using the absorbent Waterloo Biofilter, In: ASTM STP 1324, Site Characterization and Design of On-Site Septic Systems, American Society for Testing and Materials, M. S. Bedinger, A. I. Johnson, J. S. Fleming (Eds.), pp. 261–282. Jowett, E. C. and J. M. Rogers (2001) Four golf resorts re-using treated sewage for irrigation, In: Proceedings, Caribbean Water and Wastewater Association, October 2001, Cayman Island. Jowett, E. C. and M. L. McMaster (1995) On-site wastewater treatment using unsaturated absorbent biofilters. Journal of Environmental Quality. Vol. 24, pp. 86–95. Jowett, E. C., et al. (2000) Consistency of treated wastewater needed for household, irrigation and near-potable re-use. In: Proceedings, National Onsite Wastewater Recycling Association, Michigan, pp. 205–216. Millham, N. P., G. Heufelder, B. Howes and J. Costa (2000) Performance of three alternative septic system technologies and a conventional septic system. Environment Cape Cod. Vol. 3, pp. 49–58.
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Townshend, A. R., et al. (1997) Potable water treatment and reuse of domestic wastewater in the CMHC Toronto ‘Healthy House’, In: ASTM STP 1324, Site Characterization and Design of On-Site Septic Systems, American Society for Testing and Materials, M. S. Bedinger, A. I. Johnson, J. S. Fleming (Eds.), pp. 176–187. U.S. Environmental Protection Agency EPA/625/R92/004. Washington DC.
(1992)
Guidelines
for
Water
Reuse.
Yates, M.V. (1994) Monitoring concerns and procedures for human health effects. In:Wastewater Reuse for Golf Course Irrigation , Lewis Publishers, Boca Raton, pp. 143171. Author: E. Craig Jowett, Ph.D., P.Eng. President, Waterloo Biofilter Systems Inc. 143 Dennis Street, P.O. Box 400, Rockwood ON N0B 2K0 Canada www.waterloo-biofilter.com
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Figure Captions
Figure 1. (a) Above ground WATERLOO BIOFILTER configuration contained in polyethylene tanks or sheds and preceded by septic tank pre-treatment. (b) Below ground BIOFILTER configuration contained in concrete tanks, with effluent pumped or drained out of the bottom. Subsurface disposal is normal, but effluent can also be re-used for toilet flushing or higher risk forms after disinfection.
233
Low-Cost, High-Performance Wastewater Treatment and Reuse for Public Health and Environmental Protection in the 21st Century by Duncan Mara School of Civil Engineering, University of Leeds Abstract Waste stabilization ponds are a well established method of wastewater treatment, and they can easily be designed to produce effluents microbiologically safe for both restricted and unrestricted irrigation. However, they are frequently perceived as being an extremely landintensive treatment process, and this can be considered a major disadvantage especially when they are being evaluated for use in small island states. Recent research in northeast Brazil has developed pond systems that have much shorter overall retention times while retaining the ability to produce high quality effluents for agricultural and horticultural reuse. Pond design procedures are given which achieve these effluent qualities at very low per caput land area requirements, thus demonstrating that pond systems should continue to remain the wastewater treatment system of first choice in hot climates well into the 21st century. Keywords: waste stabilization ponds, design, developing countries. Introduction Waste stabilization ponds (WSP) are a well established method of wastewater treatment (Mara, 1976; Arthur, 1983), but they are generally thought to be an extremely land-intensive system and thus often not considered further for this reason. This is, of course, a mistake and we will show in this paper that WSP in warm climates do not require large amounts of land. Our research in northeast Brazil (Pearson et al., 1995 and 1996) has shown that a 1-day anaerobic pond and a 3 to 6 day facultative pond can produce an effluent suitable for restricted irrigation, and some full-scale examples exist; one of these is the 2-day anaerobic and 5-day facultative pond system at Ginebra (population: 8,000), Valle del Cauca, Colombia, the effluent from which is used for irrigating sugar cane (Figure 1).
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Low-Cost, High-Performance Wastewater Treatment and Reuse for Public Health and Environmental Protection in the 21st Century
(a)
(b)
(c)
Figure 1. The WSP system at Ginebra, Valle del Cauca, Colombia: (a) 2-day anaerobic pond; (b) 5-day facultative pond, the effluent from which is used to irrigate sugar cane (c). High-Performance “Low-Land” Wsp Assume we are to treat a domestic wastewater with a BOD (LI) of 250 mg/l, and that the design temperature (T) is 20o, the faecal coliform count (NI) is 5 ´ 107 per 100 ml, the human intestinal nematode egg count (EI) is 100 per litre, and the wastewater flow (q) is 80 litres per person per day. 235
Low-Cost, High-Performance Wastewater Treatment and Reuse for Public Health and Environmental Protection in the 21st Century
An anaerobic pond with a retention time (qa) of 1 day will have a volumetric BOD loading of 250 g/m3 day, less than the 300 g/m2 day permissible at 20oC (Mara et al., 1992). Taking a depth (Da) of 3 m, its area (Aa) is given by: Aa = qq / Da
(1)
= 80 ´ 10-3 ´ 1 /3 = 0.027 m2 / person A 6-day facultative pond with a depth of 1.5 m will have an area given by: Af = 80 ´ 10-3 ´ 6 / 1.5 = 0.32 m2 / person Three checks need to be made: the surface BOD loading (ls) on the facultative pond, its effluent BOD and the effluent nematode egg count. Surface loading. This is calculated on the basis of 60 percent BOD removal in the anaerobic pond: ls = 10 Li q / Af
(2)
= 10 ´ 0.4 ´ 250 ´ 80 ´ 10-3 / 0.32 = 250 kg/ha day – satisfactory. Effluent BOD. This is given by: Le = Li / (1 + kqf)
(3)
where k is the first-order rate constant for BOD removal in secondary facultative ponds (= 0.1 day-1 at 20oC). Thus: Le = (0.4 ´ 250 ) / [ 1 + (0.1 ´ 5)] = 63 mg/l. unfiltered BOD Since at least 70 percent of the BOD of a facultative pond effluent is due to the algae present (Pearson et al., 1988), this is equivalent to a filtered BOD of around (0.3 ´ 63) i.e. 19 mg/l, which is permissible for surface water discharge (Council of the European Communities, 1991). Effluent egg count. Egg removals in the 1-day anaerobic pond and the 6-day facultative pond are 75 and 97 percent, respectively (Ayres et al., 1992). Thus the facultative pond effluent egg count is: Ee = (Ei , = 100) (1 – 0.75) (1 – 0.97) 236
(4)
Low-Cost, High-Performance Wastewater Treatment and Reuse for Public Health and Environmental Protection in the 21st Century
= 0.75 per litre – satisfactory as < 1 per litre, the WHO (1989) recommendation for restricted irrigation. Overall area The combined area for the anaerobic and facultative ponds is (0.027 + 0.32), i.e. 0.35 m2 per person. This is extremely economic when compared with the 11 m2 per person used in France (CEMAGREF et al., 1997), and indicates quite clearly that modern WSP systems in warm climates do not require large amounts of land. Unrestricted irrigation If the pond effluent were to be used for unrestricted irrigation, for which the faecal coliform count should be below 1000 per 100 ml (WHO, 1989), then three 3.3-day maturation ponds would be required: Ne = 5 ´ 107 / [1 + (2.6 ´ 1)] [1 + {2.6 ´ 6)] [1 + (2.6 ´ 3.3)]3 = 950 per 100 ml Each of these 3.3-day maturation ponds would have an area of (80 ´ 10-3 ´ 3.3 / 1.5), i.e. 0.176 m2 per person, so the overall pond area for unrestricted irrigation would be [0.027 + 0.32 + (3 ´ 0.176)], i.e. 0.88 m2 per person – again, not an excessive amount of land. Restricted or unrestricted irrigation? The above specimen calculations show that unrestricted irrigation requires (in this case) nearly 73 percent more land than restricted irrigation. It is thus very important for the pond designer to be very clear about opting for either restricted or unrestricted irrigation as the cost difference is very significant. This is a decision best taken in association with the local farmers, but there would obviously be an engineering (and indeed municipal) preference for the lower-cost option, i.e. restricted irrigation. Wsp Effluent Quality Requirements The only effluent quality requirements (EQR) inherent in the pond design example given above are: filtered BOD >/ 25 mg/l, a nematode egg count >/ 1 per litre, and (for unrestricted irrigation only) a faecal coliform count >/ 1000 per 100 ml. These are acceptable to the European Union (which also allows WSP effluents to contain up to 150 mg suspended solids per litre) and the World Health Organization, and I would argue that they should be acceptable essentially everywhere; or, put another way, any more stringent requirement(s) should be openly justified as this would obviously have an effect on design and thus on costs (see Mara, 1996). Above all, inappropriate EQR (see Johnstone and Horan, 1994) should be resisted by WSP designers.
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References Ayres, R.M., Alabaster, G.P., Mara, D.D. and Lee, D.L. (1992). A design equation for human intestinal nematode egg removal in waste stabilization ponds. Water Research, 26 (6), 863-865. CEMAGREF, SATESE, Ecole National de la Santé Publique and Agences de l’Eau (1997). Le Lagunage Naturel: Les Leçons Tirées de 15 Ans de Pratique en France. Lyon, France: Centre National du Machinisme Agricole, de Génie Rural, des Eaux et des Forêts. Council of the European Communities (1991). Council directive of 21 May 1991 concerning urban waste water treatment (91/271/EEC). Official Journal of the European Communities, No. L135/40-52 (30 May). Johnstone, D.M.W. and Horan, N.J. (1994). Standards, costs and benefits: an international perspective. Journal of the Institution of Water and Environmental Management 8 (5), 450458. Mara, D.D. (1996). Waste stabilization ponds: effluent quality requirements and implications for process design. Water Science and Technology 33 (7), 23-31. Mara, D.D., Pearson, H.W., Alabaster, G.P. and Mills, S.W. (1992). Waste Stabilization Ponds: A Design Manual for Eastern Africa. Leeds: Lagoon Technology International. Marais, G.v.R. (1974). Faecal bacterial kinetics in waste stabilization ponds. Journal of the Environmental Engineering Division, American Society of Civil Engineers, 100 (EE1), 119139. Pearson, H.W., Mara, D.D. and Mills, S.W. (1988). Rationalizing waste stabilization pond design: the biological factor. In Water Pollution Control in Asia (Ed. T. Panswad, C. Polprasert and K. Yamamoto), pp. 691-697. Oxford: Pergamon Press. Pearson, H.W., Mara, D.D. and Arridge, H.M. (1995). The influence of pond geometry and configuration on facultative and maturation waste stabilization pond performance and efficiency. Water Science and Technology 31 (12), 129-139. Pearson, H.W., Mara, D.D., Cawley, L.R., Arridge, H.M. and Silva, S.A. (1996). The performance of an innovative tropical experimental waste stabilization pond system operating at high organic loadings. Water Science and Technology 33 (7), 63-73. WHO (1989). Health Guidelines for the Use of Wastewater in Agriculture and Aquaculture. Technical Report Series No. 778. Geneva: World Health Organization. Author: Duncan Mara School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK Fax: +44 (0)113 233 2243, Email:
[email protected]
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Treatment of Factory Waste Oily Water by B D Crittenden, S P Perera and R Mehta Department of Chemical Engineering, University of Bath Abstract An on-site waste treatment process for factory oily waste-water has been developed in order to facilitate the recycling of purified water on-site as well as the possible recycling of part, or all, of the organic components. Known as “WOWSEP”, the process has been applied at the pilot-scale for the treatment of spent metalworking fluids. The novelty of the “WOWSEP” process is that it includes an adsorption technology that uses superheated steam to drive off the soluble contaminants in situ from the internal structure of a novel synthetic carbon. The carbon is manufactured from a phenolic resin precursor which is carbonised and then activated, giving it properties that allow it to be regenerated with moderately superheated steam. Free oils are removed upstream of the carbon unit using established processes such as oleophilic mops or coalescers, and emulsified oils are treated by ultrafiltration or chemical separation. Whilst the carbon adsorption technology is unable to remove all the dissolved components from waste metalworking fluids, the reduction in COD of up to 90% in a typical cycle is substantial enough to make the process economic. Laboratory-scale studies were carried out to determine the optimum combinations of carbon type and processing conditions, including those for regeneration. Trials using a prototype rig containing 16 litres of carbon have been carried out at a site that uses a wide range of watersoluble metalworking fluids during the manufacture of automotive components. A typical flow rate was 220 litres/h. The ability of the prototype to remove water-soluble organic compounds was monitored by measuring the COD of the polished water (starting from 80 mg/litre) and comparing it with the COD of the wastewater feed (680 mg/litre). The process was allowed to continue until around 60-70% of breakthrough had occurred, at which point regeneration was started. Most of the regeneration occurred within the first 300 minutes and several regeneration cycles were carried out without loss of performance. The paper will describe (i) the performance of the carbon adsorption technology at laboratory and prototype scales, and (ii) the case study involving the prototype in order to demonstrate the potential economic advantages. Keywords: metalworking fluids; carbon adsorption; sewerage Introduction Metalworking fluids are essential components for drilling, milling, tapping and turning operations in manufacturing industry. In the UK there are believed to be around 40,000 engineering workshops that use multifunctional fluids, providing lubrication, cooling, prevention of surface corrosion and removal of metal fines or swarf, as well as prolonging the life of the machine tools. There are two types of fluid formulation. The first type comprises fluids which are mixed with water. Whilst these provide good cooling properties, they require monitoring and maintenance in order to retain their properties. Water-mix fluids
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are generally diluted to around 5% and so, although the amount of base fluid used is around 11,000 tonnes/year, the total amount of fluid in use and requiring ultimate disposal is around 220,000 tonnes/year. The second type of metalworking fluid comprises neat oils which have good lubrication and lifetime properties and require limited maintenance. Consumption of these fluids amounts to around 22,000 tonnes/year in the UK. Although the cost of the base fluid (c £2.30/litre) in a water-mix metalworking fluid is higher than for a neat oil (c £1.30/litre), there are clear economic advantages in using the water-mix formulation because of the dilution factor. The many functions of a metalworking fluid mean that an aqueous-based fluid must contain corrosion inhibitors, emulsifiers, extreme pressure agents, lubrication agents and biocides. Consequently, the wastes from aqueous-based metalworking fluids contain a mixture of free and emulsified oils, together with a mixture of water-soluble organic compounds. A typical spent aqueous-based metalworking fluid contains 5-10% free oil, 80-90% emulsion and less than 0.5% solids. Current treatment techniques can remove the solids and the free and emulsified oils on-site. Processes such as ultrafiltration and chemical treatment can be used to break the emulsions. However, the aqueous phase containing the soluble components is usually sent via a sewer to a water treatment works. Any business in the UK that discharges a trade effluent to sewer requires a consent from a sewerage undertaker who will make a charge that takes into account three factors: (i) the nature, composition and volume of the effluent, (ii) additional expense that will be incurred in order to deal with the effluent at the sewage treatment works, and (iii) any revenue that is likely to be derived by the sewerage undertaker from the effluent by way, for example, of the sale of residual sludge as a fertiliser. The cost in the UK of disposing an effluent to sewer is determined by application of the Mogden formula (Croner’s, 1991) and is discussed later in this paper. The overall aim of the project was to develop a prototype system for the cost-effective, onsite treatment of oily waste water for removing the soluble components by means of a novel regenerative carbon adsorption technology. Although adsorption of hydrocarbons from water with carbon is an established technology (McGuire and Suffet, 1983; Faust and Aly, 1987; Crittenden and Thomas, 1998), the novelty and innovation of the technology lie in the use of an in situ regenerative system that uses superheated steam for regeneration of the carbon. The overall waste oily water separation technology which comprises solids removal, emulsionbreaking and free oil removal, is known as “WOWSEP”. The prototype was constructed to be compatible with any type of pretreatment technology used to remove free oil and to break the emulsion. The prototype, shown schematically in Figure 1, receives recovered water from the pretreatment process in a collection vessel and is then pumped upwards through a column containing the carbon adsorbent. The purified water is recovered in a separate vessel either for reuse on site or for disposal at low cost since the level of dissolved oil is low. At any appropriate point, the adsorption process is stopped and the carbon is regenerated using steam superheated to 230oC. The steam is produced by an electrically heated boiler at 1 bar and its temperature is raised using an electrical in-line heater. The steam from regeneration is cooled in a condenser to produce a small volume of condensate. The overall technology therefore is essentially a concentrating device. A photograph of the prototype is shown in Figure 2. The overall performance of the
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“WOWSEP” process is determined, in part, by the performance of the carbon adsorption unit, the optimisation of which was determined from a series of laboratory-based experiments carried out at the University of Bath.
Steam generator
Carbon column
Condenser
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Pump Pump
Figure 1 Schematic of prototype carbon adsorption unit
Figure 2 Photograph of prototype carbon adsorption unit
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Laboratory-Scale Experiments Dynamic adsorption and desorption experiments were carried out on the bench-scale using a 1/2" stainless steel column packed with activated carbon in granular form. Before initial use, the system and carbon were primed with ultra-pure water. The feed, at a known concentration was then pumped upwards through the column at the desired flow rate and breakthrough curves were constructed from the total organic carbon (TOC) analyses of samples taken periodically from the effluent. Implicit in this approach was the initial assumption (later to prove invalid from a scientific point of view, although not from an industrial point of view) that the total organic fraction of the feed water could be considered to be a pseudo-single component. Adsorption experiments were carried out at ambient temperature (approx. 20oC) in order to represent typical industrial conditions. Dynamic adsorption column lengths were in the range 10-100 cm, feed flowrates were in the range 150-600 ml/hr and feed concentrations were in the range 120-11,000 mg/l TOC. Feedwaters (containing no free oil) were pretreated either by chemical splitting or by ultrafiltration. Cutting fluids and fractional components were supplied by D A Stuart Oil Ltd. Following the adsorption step, the adsorbed components were desorbed, and the carbon regenerated, by passing superheated steam in the downwards direction through the column. The steam was generated in situ in the laboratory by passing water at the desired flow rate through a preheating coil. The coil and the column were both located within a sand-air fluidised bed that could be heated to 300°C. The vapour product from the column was condensed and samples were collected for periodic TOC analysis, again making the initial pseudo-single component assumption. In situ desorption experiments were carried out with water flowrates (for steam generation) in the range 25-115 ml/hr and with column temperatures in the range 180-225oC. Supporting batch equilibrium experiments were carried out by agitating a known mass of carbon with a known volume of solution of known TOC. Agitation was carried out for a minimum of 24 hours after which the final solution TOC was measured. In order to prepare the adsorption equilibrium isotherms, it was assumed initially that the total organic fraction of the fluid behaved as a single dilute pseudo-component for the purposes of the mass balance. Other physical analysis techniques were used to support the liquid phase adsorption measurements. Dynamic adsorption-desorption and batch equilibrium experiments were carried out on a variety of novel carbons supplied by MAST Carbon Ltd (Tennison, 1998), for comparison with naturally-derived carbons supplied by Sutcliffe Speakman. MAST's carbons were manufactured from phenolic resins by the sequential processes of extrusion, drying, carbonisation, and activation to varying degrees. Granules were formed from the extrudates by crushing and grinding. MAST and Sutcliffe Speakman carbons gave broadly similar equilibrium isotherms and breakthrough curves. For adsorption, there appeared to be little effect of the degree of activation of the MAST carbon on the breakthrough curve. Equilibrium loadings at solution concentrations of 1000 mg/l TOC were 0.025 mg/mg for chemically split and ultrafiltered feedstocks, 0.13 mg/mg for pure butyl glycol, 0.06 mg/mg for pure propionic acid, and 0.018 for a pure amine fraction.
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On a dimensionless concentration basis (C/Co), breakthrough of TOC occurred very early with neat and ultrafiltered cutting fluids (Figure 3), progressing up to around 70% for the former and 30% for the latter. This was followed by a plateau region for the ultrafiltered feed and then a further rise to 100% (not shown on Figure 3). The shapes of breakthrough curves for chemically treated and ultrafiltered feedstocks were broadly similar for otherwise identical operating conditions. Breakthrough experiments with single pure compounds or compound groups, such as various organic acids, glycols and ethanolamines revealed qualitatively that the early part of the breakthrough curves was almost certainly due to premature breakthrough of amines which are corrosion inhibitors in cutting fluid formulations. For the pure components such as glycols and organic acids, the effect of changing column length was to show that constant pattern behaviour occurred. This could not be observed when cutting fluids were used because of the premature breakthrough behaviour. For the pure components, increasing the feed flowrate reduced the time to initial breakthrough and sharpened the breakthrough curve. For the cutting fluids however, the premature breakthrough masked the expected normal effect of flowrate.
C/Co (TOC) 1.00 Neat Cutting Fluid
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Figure 3 Comparison of breakthrough data for neat cutting fluid, ultrafiltered cutting fluid, and ultrafiltered cutting fluid that has been passed through an ion exchange column (100 cm column length and 150 ml/h feed flow rate). Two principal approaches were taken to deal with the amine problem. In the first, a MAST carbon was manufactured in a modified form so that it included copper to see whether the amines could be removed on to the carbon by reaction or complexing with the metal. Equilibrium isotherm experiments showed that whilst there was a slight improvement in the
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TOC loading with the copper-modified carbon, it was not sufficient an improvement to merit a breakthrough trial. It was found, in any case, that the amines remaining in solution had leached some of the copper from the carbon, and that the pH of the solution in the equilibrium cells had been unaltered. In the second approach, further pretreatment by incorporating an additional step involving ion exchange was studied. A comparison of results with neat, ultrafiltered and ion exchanged cutting fluids revealed that only by pretreating the fluid by ion exchange could the premature part of the breakthrough curve be removed, as shown in the lowest curve of Figure 3. A matrix of batch equilibrium and dynamic adsorption column experiments involving the mixed feed, the amine fraction, the remaining non-amine fraction, the carbon, the ion exchange resin, and mixed carbon/resin was then carried out to reveal that the amine and non-amine fractions were acting essentially independently of each other. Virtually independent action of the two fractions was ultimately confirmed by dynamic column experiments wherein (i) a carbon bed preceded an ion exchange resin bed, (ii) an ion exchange resin bed preceded a carbon bed, and (iii) the two solid materials were mixed together in a single bed. All these three dynamic column trials provided essentially identical breakthrough curves without premature breakthrough (shown for an ultrafiltered feedstock, for example, as the "middle" three curves in Figure 4).
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Figure 4 Effect of ion exchange before, after and mixed with the carbon
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Further evidence of the independent behaviour of the amine and non-amine fractions was provided by the success in modelling the breakthrough curve of the non-ion exchanged cutting fluid by a simple addition of the breakthrough behaviours of the amine and the nonamine fractions of the pretreated cutting fluid. Regeneration of both MAST and Sutcliffe Speakman carbons could be accomplished with steam at 1 bar and modest superheat (around 200oC). The mass flowrate of the steam was low compared with the flow rates used in the preceding adsorption step in the cycle. Over the range 25-75 ml/hour, the steam mass flow rate had little effect on the regeneration curves. Additionally, the time for regeneration was substantially lower than the time to reach complete breakthrough on the adsorption step in the cycle. The column effluent TOC rose quickly to a maximum to decline exponentially towards zero (shown as a function of regeneration temperature for chemically split feedstock in Figure 5). The magnitude of the peak TOC concentration increased, whilst the time to this peak and the peak width were reduced, as the steam temperature was increased. These relationships were linear over the range of conditions studied. Subsequent water mass balances showed that the ratio of regeneration water to feed water varied with regeneration temperature but was in the range 7-23%, thereby providing good concentration factors for the organic fraction adsorbed. The lowest ratio was found with the highest regeneration temperature tested (225oC). Regeneration took longer, and hence more water was required, when the regeneration temperature was lowered. The exponential reduction in effluent TOC concentration on regeneration beyond the peak concentration could be modelled by a first order process with a relatively high apparent activation energy of about 70 kJ/mol. This has facilitated development of a simple model for design purposes. Additionally, although there was no effect on the adsorption breakthrough curve, there was some effect of the MAST carbon activation on the regeneration performance. Repeated dynamic adsorption experiments, firstly with fresh carbons and secondly with the same batch of carbon over five complete adsorption-desorption cycles revealed good repeatability. The approach to cyclic steady state was fast. Mass balances over a large number of individual adsorption-desorption cycles showed that, within the bounds of experimental error, the mass of material adsorbed was equal to that removed on regeneration, providing further evidence that the carbons could sustain repeated cycles. The substantial amount of data obtained from the bench-scale apparatus allowed an adsorption column-sizing algorithm to be designed in order to support the commercial development of the “WOWSEP” process. The pre-treatment units of the overall “WOWSEP” process did not require the development of special design algorithms. Prototype-Scale Experiments The prototype system shown in Figures 1 and 2 contained 16 litres of carbon and was operated with an average feed flow rate of 220 litres/h. The total volume of feed was 4000 litres having an average COD of 680 mg/l. The results of a breakthrough trial are shown in Figures 6 and 7 for the adsorption and desorption steps, respectively. Figure 6 shows that the
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breakthrough occurred immediately to be followed by a gradual increase in effluent COD. This was as expected from the laboratory-scale experiments. The lowest COD was 79 mg/l and the final COD in this trial was 680 mg/l. A typical regeneration profile is shown in Figure 7. As expected from the bench-scale experiments, there was a peak in the effluent COD shortly after the regeneration process was started and most of the regeneration occurred in the first 300 minutes. The volume of condensate was 600 litres and so the volume concentration was 6.67. Case Study A computer spreadsheet was developed in order to determine the financial benefits from pretreatment and polishing with the carbon bed. An example case study is provided by Envirowise (2001). The spreadsheet is based not only on the technical capabilities of the “WOWSEP” process but also on the charging structure for disposal of aqueous effluents in the UK. The Mogden formula (named after the sewage treatment works where it was first used) is used in the UK to calculate the charge for the reception, conveyance, treatment and disposal of waste arising from a trade effluent discharge to sewer. The method is aimed at ensuring that a company only pays for the treatment that an effluent receives. The charge is a function of the volume and strength of the effluent and the degree of treatment afforded to it. The formula can vary throughout the UK but a common form is as follows: C = R + [V + Bv] + B[Ot/Os] + S[St/Ss] where the parameters are defined in Table 1. R, V, B and S are the regional average unit costs while B and S are multiplied by factors which relate the strength and solids content of the trade effluent to that of domestic sewage. There is much regional variation in charges. Example values for Anglian Water (extending throughout the Eastern region of England) for 1997/98 are shown in Table 1. It is clear that reductions in cost can be achieved not only by reducing the volume of sewage which can be achieved if water can be recycled within the manufacturing environment, but also by reducing the chemical oxygen demand. In the following example of the economics of the “WOWSEP” process, it is assumed that the COD of the initial wastewater is 100,000 mg/l and that this value can be reduced to 15,000 mg/l on pretreatment. It is assumed also that the COD of the final aqueous stream after carbon adsorption is 4,500 mg/l. For an engineering company that produces 1000 m3 per year of oily wastewater, the net annual treatment costs would be £10,500 (at 1999 prices) if the recovered water (c 950 m3) were to be recycled. The net annual treatment costs would be £12,600 if the recovered water could not be recycled. Without treatment, the oily wastewater would have cost £40,000 per year if it were to be tankered off-site for disposal. Thus, net annual cost savings of £29,500 could be realised with the “WOWSEP” process if the recovered water were to be recycled. If recycling of water were not possible, the net annual cost saving would be £27,400.
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Concentration (mg/l TOC) 14000
225 C
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COD mg/l 11000 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 0
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Figure 7 Typical regeneration profile for prototype Table 1 Parameters in the Mogden formula and some typical values (Croner’s, 1991) Parameter
Definition
B
biological oxidation cost per m3 of settled sewage, including the cost of secondary sludge disposal additional cost per m3 where there is biological treatment total charge in pence/m3 of trade effluent chemical oxygen demand (COD) in mg/l of average strength settled sewage chemical oxygen demand in mg/l of the trade effluent after settlement for a specified period (usually one hour) reception and conveyance cost/m3 of sewage treatment and disposal cost of primary sludges/m3 of sewage total weight of suspended solids (mg/l) of average strength crude sewage total weight of suspended solids (mg/l) of the trade effluent volumetric + primary treatment cost per m3 of sewage treated
Bv C Os Ot R S Ss St V
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1997/98 values (Anglian Water) 38.66 p/m3 3.46 p/m3 465 mg/l
11.42 p/m3 21.88 p/m3 383 mg/l 17.88 p/m3
Treatment of Factory Waste Oily Water
Conclusions An integrated process has been developed to facilitate the recycling of water by the treatment of factory waste oily water. Dissolved oils are removed by adsorption onto a novel, synthetic carbon derived from a phenolic resin precursor. The benefits (Envirowise, 2001) include: • • • • • •
a reduction of up to 95% in wastewater COD; reduced cost of disposal to sewer or removal by tanker; potential reuse of water onsite; savings on the purchase of mains water; reduced carbon disposal and reprocessing costs; and compliance with current and future legislation.
References Crittenden, B D and Thomas, (1998), Adsorption Technology and Design, ButterworthHeinemann, Oxford, 1998. Croner’s Waste Management, (1991), Croner Publications Ltd, Kingston upon Thames, pp 2389 to 2-390. Envirowise (2001), Cost Effective Treatment of Waste Oily Water, Case Study CS92, Envirowise, AEA Technology Environment, Harwell. Faust, S D and Aly, O M, (1987), Adsorption Processes for Water Treatment, Butterworths, Boston, 1987. McGuire, M J and Suffet, I H, (1983), Treatment of Water by Granular Activated Carbon, American Chemical Society, Advances in Chemistry series, No 202, Washington. Tennison, S R, (1998), Phenolic-resin-derived activated carbons, Applied Catalysis, Vol 173, pp. 289-311. Acknowledgments The authors gratefully acknowledge the Department of Trade and Industry, the Engineering and Physical Sciences Research Council, and the Environmental Technology Best Practice Programme (now known as Envirowise) for joint financial sponsorship of this research programme. Use of material provided for the Envirowise case study is acknowledged. The authors are also grateful to their industrial partners which include: Alpha Construction Ltd (Hilton, Derbyshire), BTR Environmental (Guildford, Surrey), Ford Motor Company (Basildon, Essex), MAST Carbon Ltd (Guildford, Surrey), OPEC Ltd (Batley, West Yorkshire), PERA Technology Centre (Melton Mowbray, Leicestershire), and D A Stuart Oil Ltd (Wolverhampton, West Midlands). Authors: B D Crittenden, S P Perera and R Mehta Department of Chemical Engineering University of Bath, Bath, BA2 7AY, UK tel: +44 1225 826501 E-mail:
[email protected]
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Manhole Rehabilitation Strategies: A Cost Effective Analysis by L. Andrea Williams-Lewis, B.Sc., M.S.C.E. Central Water and Sewage Authority, St. Vincent and the Grenadines Abstract Caribbean citizens are dependent on the public and private infrastructure to provide essential life supporting services such as electric power, air-conditioning, potable water, sewage disposal and treatment, drainage, communications and transportation. However many of the infrastructure systems are facing the end of their design life and have suffered from chronic lack of maintenance. Another major problem facing Caribbean infrastructure is overloading. The rate of growth of Caribbean urban population has outpaced that of its infrastructure. Deteriorating infrastructure affects not only human health and safety but also the economic strength of a nation. Sewer systems have traditionally been some of the most neglected parts of Caribbean infrastructure as their subsurface nature ensures that they remain out of sight. However, sewer system failure may at times occur with catastrophic effect. The effects of sewerage system overload are many. The cost of sewage treatment has been rising steadily as fuel prices surge. One of the many problems facing sewerage systems in the Caribbean is the problem of inflow/infiltration (I/I). Manholes, the inspection points of the sewerage system are major contributors to this problem; they are however, the cheapest part of the sewerage system to repair. Manhole rehabilitation therefore presents a cost effective means of reducing I/I and thus reducing treatment plant overload and cost. There are various manhole rehabilitation techniques and products available. These range from the more common cementitious, acrylic and polyurethane grouts sprays, and liners to the less common fiberglass replacement manholes. This paper examines and compares these techniques, their application procedures, life span and cost. The paper also explores the repair and rehabilitation of manholes as a cost effective means of reducing I/I. As part of this study a manhole survey was performed in Kingstown St.Vincent and the manholes categorized according to the Manhole I/I rating schedule found in American Society of Civil Engineers ASCE Manual “Reports on Engineering Practice no. 92, Manhole Inspection and Rehabilitation.” The inspection was done in order to quantify the amount of I/I contributed by the manholes, ascertain the extent of their deterioration and to select the most cost effective rehabilitation method. The feasibility of rehabilitation is also investigated by comparing the cost of rehabilitation to the cost savings in pumping and treatment resulting from reduced I/I over the life cycle of the rehabilitation. Key Word Inflow/Infiltration Manhole Net Present Value Rehabilitation
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
1.0 Introduction 1.1 Deteriorating Infrastructure Caribbean utility infrastructure has been continually plagued with problems. Power outages and water shortages may now be becoming things of the past yet our utility infrastructure still needs a lot of attention. We have been spending billions on up grading our road networks and cleaning up our environment, the multi-million dollar Organisation of Eastern Caribbean States, OECS Solid Waste Management Project, the Roseau dam in St.Lucia, the million dollar Dalaway water supply project in St.Vincent are prime examples of this. Meanwhile our sewer systems continue to suffer from years of neglect and a reactive approach to maintenance. 1.2 Sewer System Repair Sewer system repair is one of the easiest ways of cost reduction in utility spending; and may drastically increase the capacity of some of our treatment plants. As some of our sewage treatment plants become upgraded to reduce the amount of pollution of receiving waters, the capital and operational costs are staggering. We can no longer ignore the money that is going down the drain due to defects in the sewerage system. Sewer system repair can cause major disruption to life above ground. However, technology available to extend the life of existing systems without disruption above ground facilities has undergone tremendous explosion in the last few years. 1.3 Manholes In a study performed in 1994 by Wade and Associates, a Kansas, United States consulting engineering firm specializing in collection system rehabilitation, it was shown that manholes contribute 30% of Inflow/Infiltration, I/I within the systems they studied, however the cost to rehabilitate the manholes and eliminate that I/I was only 10% of total repair costs. This indicates that manhole rehabilitation is an important and cost effective part of any sewer maintenance program (Nance and Hughes 1999). Figure 1.1 Cost Effective I/I Reduction Cost Effective I/I Reduction 50 45 40
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
In this paper, a very simple method of manhole inspection will be highlighted. A case study of such on inspection done on the campus of Purdue University, West Lafayette Indiana, USA is presented along with the results of that study. Some of the manholes in Kingstown, capital city of St.Vincent were also investigated and those findings will also be presented. 2.0 Methodology 2.1 Purdue University Case Study Purdue University sewerage system was first constructed in or about 1869 when the university was founded. Since then, there have been numerous additions and expansions in the 1930’s 1950’s and 1970’s to cater for the growing university population. At peak times the Purdue sewerage system serves some 50,000 people. The sewerage system is made up of about 125 miles of lines comprised of five 24” trunk sewers, force mains and laterals. There are three primary lift stations and numerous ejector pumps in basements of buildings on campus. The entire area serviced is about 1680 acres. There are also about 500 manholes in the system which range in depth from 4 feet 24 feet. 2.1.1 Treatment costs Sewage from Purdue University is pumped to the West Lafayette wastewater treatment plant where it is treated and then released into the Wabash River. As of January 2000 the cost of sewage treatment will be $2.66/1000 gallon treated at the West Lafayette treatment plant. The average treatment cost in the United States per 1,000 gallons is $1.75 (Benitz 1999). 2.2 American Society of Civil Engineers, ASCE, Guidelines For the purpose of this case study a manhole inspection form was adapted from the ASCE Manual and Reports on Engineering Practice No. 92. (See Appendix 1) The aim of the inspection process undertaken during this study was to quantify the amount of I/I contributed by the manholes. However, the structural condition of the manholes was also taken into consideration as it was felt that structural condition would also affect the type of rehabilitation used. The inspection form shown in Appendix 1 provides general information about the manhole, its location and construction type. It is important to determine the exact location characteristics of the manhole. A manhole located in a grassed yard would have different I/I contribution from an identical manhole located in a paved area because of the different run-off characteristics. Each component is evaluated separately. The component’s contribution to I/I is established by the presence of watermarks or mineral deposits. The structural condition is evaluated based on the presence of cracks (in precast manholes) and missing mortar in brick manholes. Rating system A rating system is used for each component of the manhole; both the component’s structural condition and its contribution to I/I are rated. The ratings range from 1, where there is no evidence of I/I, to 5, where there is severe I/I. The structural rating system also ranges from 1 to 5 with 1 indicating good structural condition and 5 deteriorated structural condition. Appendix 2, Table 1 and 2 show the I/I and structural rating systems respectively. The numbers located above the rating description correspond to that component’s contribution to I/I expressed in
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gallons per minute (gpm). The covers contribution to I/I were not given in the two tables but calculated from Equation 1 in Appendix 2.
3.0 Results And Analysis Thirteen manholes on Purdue University campus were surveyed. They constituted a representative sample of the five hundred manholes on campus. The results of the survey are tabulated in Tables 1 to 13 in Appendix 3. The structural rating (Table 1 Appendix 2) and the I/I rating (Table 2 Appendix 1) were added to give a combined rating. The manhole component with the highest rating may be repaired first. The ratings for the manhole (manhole 1) pictured in Figures 3.1, 3.2 and 3.3 are compiled in Table 3.1. Each component of manhole 1 is analyzed separately in order to determine its I/I and structural ratings. Cover The cover is given a structural rating of four as it is deteriorated and corroded. An I/I rating of three is given because the bearing surface was corroded (Table 1, Appendix 2). The combined rating was thus seven. There are two holes in the cover, it was therefore estimated that it would allow the passage of 9.46 gpm I/I. (Table 3, Appendix 2)
Figure 3.1 Manhole cover Frame, Frame seal and Chimney The frame was given a structural rating of four as it is severely corroded. The chimney was given a structural rating of two and an I/I rating of four because it exhibited signs of mineral deposits. (Table 1, Appendix 2) Mineral deposits
Figure 3.2 Frame, Frame seal, and Chimney Cone, Wall, Bench and Channel The cone and wall were given structural ratings of two because there were a few hairline cracks present. An I/I rating of three was given because of the presence of watermarks. The manhole was surcharged the bench and channel were therefore invisible. The steps were severely deteriorated as were all of the steps seen and so were given a structural rating of four.
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
Similar analyses were made for the other manholes and the results tabulated in Tables 1 through 13 in Appendix 3. The total estimated I/I was found by adding the individual estimated I/I of the manhole components
Figure 3.3 Cone, Wall, Bench, and Channel
Table 3.1 Manhole 1 I/I and Structural Rating Manhole Structural I/I Combined Estimated Component Rating Rating Rating I/I (gpm) Cover *Frame Frame seal Chimney Cone Wall Bench Channel * Step Pipe seal
4 4 4 2 2 2
3 3 4 3 3
4
7 7 7 6 5 5 **NV NV 4 NV Total Estimated I/I
9.46 0.4 0.4 0.8 0.4 0.2
11.66
* No I/I rating ** Not visible
3.1 I/I Calculations The total estimated I/I from all of the manholes surveyed was found by adding the individual estimated I/I from each manhole. Inflow was calculated as the contribution of the cover, frame
254
Manhole Rehabilitation Strategies: A Cost Effective Analysis
seal, and chimney, and only occurred on days when it rained. The average number of rain days over the past five years was calculated using rainfall data for Purdue found at http:/shadow.agry.purdue.edu. The number of days per year that received rainfall of one inch and over was ascertained, and an average of these days taken for the years 1994 to 1998. Infiltration was calculated as the I/I contribution of the cone, wall bench, and channel. 3.1.1 Yearly Inflow Total inflow: (cover, frame seal and chimney contribution) = 260.62 gpm Average number of days per year rainfall was 1 inch or more = 7 days Total estimated yearly inflow = (Inflow (gpm)) x (min/hr) x (hr/day) x days/year Inflow = 260.62gpm x 60 min/hr. x 24 hrs/day x 7 days/year = 2,627,050 gallons per year 3.1.2 Yearly infiltration Total estimated infiltration was found by adding the infiltration contribution of each manhole. Infiltration is considered a daily occurrence thus, the yearly amount of infiltration was estimated as follows. Total Estimated Infiltration = 5.2 gpm Total estimated yearly infiltration = (infiltration (gpm)) x (min/hr) x (hr/day) x days/year 5.2 gpm x 60 min. x 24 hrs. x 365days = 2,733,120 gallons per year 3.1.3 Total estimated I/I Yearly I/I was estimated as the sum of yearly inflow and infiltration. Total yearly I/I = 2,733,120 + 2627.049.6 = 5,360,170 gallons per year 3.1.4 Treatment cost of estimated yearly I/I The treatment cost was calculated using a value of $2.66/1000 gallon attained for Purdue Physical Facilities Department. Total I/I gpy x Treatment cost/1000 gallon = (5,360,170 x 2.66)/1000 = $14,254.00 per year. These results are summarized in the following Table 3.2. Table 3.2 Estimated I/I and Treatment Cost Estimated Inflow Estimated Infiltration 2,627.049.6 2,733,120
Estimated I/I 5,360,170
Treatment Cost $14,254.00
3.2 The decision making process Many factors have to be considered when making a decision regarding choice of a method and product. Among them are: · Sewer environment For sewers that have a very corrosive environment e.g. sewers located in tropical regions, special consideration should be given to corrosion resistant products · Equipment and training necessary Many rehabilitation methods require complex equipment, application methods and highly trained personnel. A small authority with little funds available for rehabilitation may not be able to afford to use these methods of rehabilitation. · Disruption of above ground conditions 255
Manhole Rehabilitation Strategies: A Cost Effective Analysis
In areas that are highly congested open cut methods often cause disruption to life above ground. · Speed of process The speed of the process determines the productivity. Low productivity may mean higher costs. These costs may be both financial and social. Most sewers run in the middle of the street any work being carried out on them will cause and general traffic disruptions. · Design life of rehabilitation method Different rehabilitation methods have different life spans. A portland cement repair product has a shorter life span than a polymer repair product. · Cost Products that are more expensive are not necessarily better products; thus, the best value for money must be sought. Products must therefore be analyzed by considering the time value of money and the estimated life span of the product. 3.4 Cost comparison of different rehabilitation products The selection of a product for rehabilitation depends on its applicability and design life, while these factors are important the final decision on a repair method is usually made based on cost, all other things being equal. It is quite easy to evaluate different products based on initial cost, however, each product has a different design life, and this will influence the final cost of the product. The cost of various manhole products are summarized in Tables 3.3 and 3.4 the costs are calculated per linear foot of a 48” diameter manhole (adapted from “Manhole Inspection and Rehabilitation” Hughes 1999). When considering manhole rehabilitation there is seldom one type of repair that will eliminate all problems encountered. A mixture of different types of repair methods must be used in order to achieve the desired objective. Factors like the age, condition and type of manhole all influence the rehabilitation procedure to be used in a specific manhole. For example, I/I control may require different types of rehabilitation from that used to control corrosion due to sulfuric acid.
· · · · ·
Table 3.3 Cost comparison of manhole inserts (Hughes 1999). Manhole inserts Cost per insert $20 - 130 Hole plugs, inserts, dishes $275 - 415 Chimney seals $250 – 415 Adjusting rings $120-$240 New cover $415-685 Replace frame
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
Table 3.4 Cost comparison of manhole rehabilitation techniques (Hughes, 1999). Rehabilitation technique Cost range per linear foot Cementitious grouts $135 Chemical grouts $45-95 Cementitious coatings $75-190 Polymer coatings $90-250 Thermoplastic liners $300-600 Cured in place liners $200-400 Replacement $2,400-5000
Figure 3.4 is a graphical representation of the data in table 3.4 Cost comparison of manhole re habilitation te chnique s
Cost per linear foot
$4,000 $3,500
Chemical grouts
$3,000
Cementitious coatings
Polymer coatings
$2,500
Cured in place liners
$2,000
Thermoplastic Liners
$1,500
Replacement
$1,000 $500 $0
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
There are certain factors involved in choosing a rehabilitation which are very difficult to quantify, for systems with shorter life expectancy there can be additional inspection and surveys, public disruption and safety issues as well as potential political consequences (Hughes 1999). In addition, a factor in choosing a rehabilitation product is ease of installation and installation productivity. Table 3.5 summarizes the initial cost and life span (life spans were the estimation of the manufactures of the products) and present value of the different manhole rehabilitation products.
Table 3.5 Initial Cost and Estimated Life Span of Rehabilitation Products Rehabilitation Product Initial Cost Estimated life span Present value (yrs) Chemical grouts $70 30 $184 Portland cement grout $125.00 10 $213.9 Calcium aluminate grout $145 20 Polymer coatings $170 30 $205 Thermoplastic liners $450 60 $450 Cured in place liners $400 60 $400 Replacement method $3700 60 $3700 In order for a decision to be made from among the different rehabilitation products, they must all be placed on a level playing field. Present value analysis is used to compare the cost of the different methods. A present value analysis takes into consideration the time value of money and the impact of inflation. An inflation cost of 2.5% and a discount rate of 8% is used in the analysis (Hughes 1999). This analysis was done over a period of sixty years. Sixty years was chosen because it is the maximum life span that can be achieved by any repair method and is a multiple of life spans of all of the products being considered 3.4.1 Rehabilitation Decision Decisions on the type of rehabilitation to be used for each manhole were made based on: · Knowledge gained from literature review and attending “Trenchless Technology” seminars. · Mr. Wayne Love, of Raven Lining Systems marketing department was also consulted. · Cost comparison of the different products are summarized in Table 3.5 The major repair methods chosen were chemical grouting and spray applied polymer coating. Many of the manholes examined were brick manholes, with missing mortar. Chemical grouts should be used to first fill these voids. The manholes should then be coated with a polymer coating. All of the manhole steps should be removed as they were severely deteriorated and presented more of a safety hazard than a means of getting into the manholes.
258
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Polymer coatings was chosen as the primary rehabilitation method for the following reasons: · Most of the manholes surveyed were brick structures. This type of structure lends itself very well to the coating process. · The structures examined suffered from severe sulfide corrosion as evidenced by the deteriorated steel steps. Thus, a corrosion resistant rehabilitation method was necessary. · In a recent study polymer coatings proved 68.7 % more cost effective than cementitious and 36.1% more cost effective than calcium aluminate coatings (Hughes 1999). · Polymer coatings have a longer estimated life span than cementitious and calcium aluminate coatings and provide excellent corrosion resistance. · Polymer coatings are relatively easy to apply. 3.5 Estimated Cost of Rehabilitation Rehabilitation cost was estimated per linear foot of manhole. The total linear feet of manholes surveyed is 254ft. Table 3.6 summarizes the rehabilitation costs. Table 3.6 Estimated Rehabilitation Costs Grouting Coating Cost Total Per Foot Linear Cost Per Foot Feet 254
$70.00
$170.00
Total Replace frame Rehabilitation Cost and cover $17,780.00 $43,180.00 $9,490.00 $70,450.00 Total Grouting Cost
Total Coating Cost
Table 3.7 shows the total estimated yearly treatment cost for I/I and the total estimated cost of rehabilitation. Table 3.7 Estimated I/I and Rehabilitation Cost Total Treatment Costs Total Rehabilitation Costs $14,254.00 $70450.00
3.6 Cost-effective Analysis of Repairing Manholes The next step in the I/I analysis is a cost analysis of the repair methods chosen. Although all of the manholes surveyed showed evidence of I/I, this I/I cannot be eliminated unless its elimination is cost effective. Similar to the calculations made for selection of the best rehabilitation method, a present value analysis is used to ascertain the savings over the estimated life of the chosen rehabilitation method. 3.6.1 Present Value Analysis In this study, the approach used to assess the cost effectiveness of rehabilitating the manholes was to compare the cost to reduce I/I with the cost to continue to transport and treat these flows. The cost to reduce I/I was calculated previously, as $70,450.00 while the treatment cost was $14,254.00 the calculations were made considering 2000 as the base year.
259
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Life of Repair (yrs) 0 10 15 20 25 30 35
Table 3.8 Estimated Cost Savings Present Value Treatment Estimated Savings Cost $14,254.00 -$56,200 $108,136 $37,686 $144,360 $73,910 $172,253 $101,803 $193,731 $123,281 $210,269 $139,819 $223,004 $152,554
The results shown in Table 3.8 show that rehabilitation is indeed cost effective. A saving of over $139,000 may be realized over a thirty-year life span. Figure 3.5 gives a graphical representation of these results. These calculations were made using, 8% interest rate, and 2.5% rate of inflation. Figure 3.5 Estimated Savings vs. Life of Repair Estimated Saving $200,000
Estimated Saving
$150,000 $100,000 $50,000 $0 ($50,000)
0
10
15
20
25
30
35
($100,000)
Life span of repair (yrs)
3.6.2 Pay Back Period The pay back period is a type of analysis used in capital budgeting decision-making. It was the first formal method used to evaluate capital budgeting projects. It is defined as the expected number of years required to recover original investment. Although this type of analysis is not recommend for use in rigorous cost analyses, in this case it enables the minimum life of repair to be calculated. As shown in Figure 3.5 the payback period for using the chosen rehabilitation technique of chemical grouting and polymer coating is over five years. Most repair methods have a life span that exceeds this time. If maintenance work has to be done on the manholes before this time then the cost savings shown Table 3.8 would change to reflect this. Thus, the cost savings are calculated on the premise that repair is not needed for the duration of the life span of repair. 260
Manhole Rehabilitation Strategies: A Cost Effective Analysis
3.6.3 Sensitivity Analysis The variables that have been used to estimate the savings expected from rehabilitation are subject to some type of probability distribution and hence are not known with certainty. Sensitivity analyses are used to test how the value of the estimated savings would change with a change in discount rate or inflation rate. Discount rates of 6%, 7%, and 8% are used keeping the inflation rate constant at 2.5%. Figure 3.6 represents the sensitivity of estimated savings to change in discount rate.
Estimated Savings
Sensitivity of Estimated Savings to Change in Discount Rate $250,000 $200,000 $150,000 $100,000 $50,000 $0 6
7
8
Discount Rate (%) Figure 3.6 Sensitivity of Savings to Change in Discount Rate Figure 3.6 shows that estimated savings in inversely proportional to the discount rate. A twopercent decrease in discount rate results in a 26% percent increase in estimated savings The inflation rate is varied keeping the discount rate fixed at 8%. Figure 3.7 shows that as the rate of inflation increases the estimated savings also increases. A two- percent increase in the rate of inflation results in an increase of about 28% in estimated savings. Figure 3.7 Sensitivity of Estimated Savings to Rate of Inflation
Estimated Savings
Sensitivity o f S avings to R ate o f Inflatio n $ 300,000 $ 250,000 $ 200,000 $ 150,000 $ 100,000 $50,000 $0 3
4 R ate of Inflation (% )
261
5
Manhole Rehabilitation Strategies: A Cost Effective Analysis
4.0 Kingstown 4.1 Introduction The Kingstown sewerage system was installed in the early 1970’s and serves the central commercial district. Over the years, there have been various extensions to this system. It comprises around 5800m (19000 ft) of sewers which range from 150 mm to 600mm in diameter. Flows from the existing system gravitate to a main pumping station in a central downtown location from where flows are pumped untreated to a 400 mm diameter sea outfall which extends about 1400 m around the northern edge of Kingstown Bay to discharge at Old Woman Point. The outfall is in poor condition with a number of cracks in it and it currently discharges through a break at a point about 300m off the Edinboro beach to the west of Kingstown harbour. (Howard Humphrey’s, 1997) This break in the outfall pipe results in the pollution of the bathing beach at Edinboro. Figure 4.1 Break In Outfall Pipe
There is only one operational pump at the sewerage pumping plant; therefore, sewage is pumped only twice daily. The rate of pumping is therefore about 100 gpm. The rest of the sewage is allowed to overflow out into the receiving waters. In recent times studies have shown that there has been a reduction in the dorsal fish species and been destruction of coral reefs in the area.
262
Manhole Rehabilitation Strategies: A Cost Effective Analysis
4.2 I/I Contribution St.Vincent and the Grenadines received an average rainfall of about 6.5 in during the rainy season of 2000 (St.Vincent Meteorological Office). This amount of rainfall results in ponding around low-lying manholes and contributes significantly to I/I. Some of the sewerage lines in Kingstown are only few inches below seawater and this also causes infiltration of ground water into the sewers. 4.3 Manhole Inspection In an effort to determine the contribution of I/I on the Kingstown sewerage system a similar study was undertaken to the one that was performed at Purdue. Unlike those at Purdue University, the manholes surveyed in Kingstown were in less of a state of disrepair and were mostly made of precast concrete. The most pervasive defect seen in these manholes was leaking around the pipe seal area. This may be due to poor construction.
Figure 4.2 Manhole cover with insert Table 4.1 Manhole Component Cover *Frame Frame seal Chimney Cone Wall Bench Channel * Step Pipe seal
Figure 4.3 Manhole showing defective wall/pipe joint
Structural Rating
I/I Rating
Combined Rating
Estimated I/I (gpm)
1 1
2
3
9.46
7
0.4 0.2
4 NV NV 5
3 3 NV NV 5
NV NV 10 Total Estimated I/I
NV-Not Visible 263
0.8 10.86
Manhole Rehabilitation Strategies: A Cost Effective Analysis
It is feasible, that grouting around the pipe seals will significantly reduce inflow and thus reduce treatment costs as well as sea pollution. 4.4 Sewerage Costs While the present sewage pumping cost is relatively insignificant, the broken sewer outfall pipe allows for pollution of the Kingstown harbour. Reduction in the volume of sewage reaching the outfall is thus quite desirable. The cost of sewerage plant operations and maintenance is about (EC) $4500 monthly. There are however plans to construct a new sewerage system in Kingstown and along the south east coast of the island. The proposed upgrade will cost some (EC) $21,000,000, as of 1997. This is a significant investment. It is therefore necessary to eliminate excess I/I from the sewerage system, as the future cost of treatment will be much greater than it is at present.
5.0 Conclusions · The manhole inspection described in this study provides an easy and cost efficient way of assessing manhole condition. It may be used as a first step in any sewer rehabilitation program. ·
It is easy to quantify the financial benefits that result from a rehabilitation program.
·
Reduction in treatment plant costs is the first financial evidence that is seen in manhole rehabilitation.
·
There are however, costs that cannot be easily quantified. There are several social and environmental benefits associated with manhole rehabilitation.
·
Manhole rehabilitation cannot be undertaken in isolation. If only part of the sewerage system is repaired, I/I may tend to migrate to other parts of the system.
·
Kingstown sewerage system is in need of major upgrades and extension. It is hoped that this work will come on stream soon. However, the rehabilitation of existing manholes is necessary for the economic functioning of proposed treatment facilities.
·
While most Caribbean islands may not be able to afford a total sewerage rehabilitation, manhole rehabilitation may be considered as a cost effective way of reducing their treatment plant costs.
·
The manhole survey used in this study may be used to schedule rehabilitation, with the manholes with the highest ratings being repaired first. The survey may also be used as a first step in a sewer system evaluation survey, SSES.
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
References
American Society of Civil Engineers, (1983). “Manuals and Reports on Engineering Practice NO. 62 Existing Sewer Evaluation and Inspection.” New York, NY. American Society of Civil Engineers, (1982). “Manuals and Reports on Engineering Practice NO.60 Gravity Sanitary Sewer Design and Construction.” New York, NY. American Society of Civil engineers, (1997). “Manuals and Reports on Engineering Practice NO.92 Manhole Inspection and Rehabilitation.” New York, NY. Ausuber, J. H. and Herman, R. (1988). “Cities and Their Vital Systems Infrastructure Past and Present.” Series on Technology and Social Priorities National Academy of Engineering, Washington, D. C. Benitz, W. (1999). “Chemical Grouting,” Technical Presentation Trenchless Technology Sewer and Water Line Rehabilitation Seminar Austin, Texas, November, 9-10, 1999. Brigham, E. F., and Gapenski, L. C. (1997) Financial Management Theory and Practice. Orlando, Florida. Brousseau, E. (1997) “ Trenchless Sewer Construction vs. Reconstruction.” Paper presented at First Nations Services Corporation, Annual Sewer Conference, Orillia Ontario, Canada, 1997 Choate, P., and Walter S. (1983) America in ruins: Beyond the Public Works Pork Barrel.” Council of State Planning Agencies, Washington, DC. Dombrow, B. A. (1965). Polyurethanes, Reliance Publisher’s, Harrison, New Jersey. Gillani, S. (1998). A comprehensive Review of Innovative Materials and Technologies for Sewer System Rehabilitation, Masters Research Study, School of Civil Engineering, Purdue University, West Lafayette, Indiana. Howard Humphreys & Partners Ltd. (1997) “ Study To Review the Treatment and Disposal of Kingstown’s Sewerage, St.Vincent.” http:// www.avantigrout.com http://www.cretexseals.com/featured.htm http://www.a-lok.com/forms/alok3asp http://www.containment http://www.rapid seal.com/description.html
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
Hughes, J. (1999). “Polymers in Underground Concrete Rehabilitation.” Proceedings of the Conference American Society of Civil Engineers, May 10 –12, 1999, Cincinnati, Ohio. Mailvaganam, N. P. (1991) Repair and Protection of Concrete Structures. CRC Press Inc., Boca Raton, Florida. McGovern, S. (1999) “Can Coatings Protect Wastewater Treatment Systems?” Concrete Construction, 44 (4), 53-57. Nance, S. (1999), “Manhole Inspection and Rehabilitation” Technical Presentation Trenchless Technology Sewer and Water Line Rehabilitation Seminar Austin, Texas, November 9-10, 1999. Nance, S. and Hughes, J. (1999). “Corrosive Underground Environments” Public Works Engineering, Construction and Maintenance, Tulsa, Oklahoma National Association of Sewer Service Companies (1996), “Manual of Practices Waste Water Collection Systems.” Maitland, Florida. National Center for Environmental Research and Quality Assurance (1999) “Rehabilitation of Urban Infrastructure” http:// es.epa.gov.ncerqa/sbir/sbir97/rehab.html Peterson, A.C. 1971 Applied Mechanics of Fluids, Ames, Iowa. Avanti International, 1995. “How to Plan a Chemical Grout Program.” Public Works 126 (11) 56-57 Sullivan, R. H., and Foster, W. F. (1982) “ Status of Sanitary and Combined Sewers in the USA.” Proceedings of Maintenance, Repair, Renovation and Renewal of Sewerage Systems, Institution of Civil Engineers, London, June 22-24, 1981. Tchobanoglous, G. (1981). Wastewater Engineering: Collection and Pumping of Wastewater. McGraw-Hill, Inc. New York. Tchobanoglous, G., and Franklin, B. L. (1991). “Wastewater Engineering: Treatment Disposal and Reuse” McGraw-Hill, New York. Wade, M. (1991). “ Manhole Rehabilitation” ASCE, Civil Engineering, 61 (10), 59-60. Author: L. Andrea Williams-Lewis, B.Sc., M.S.C.E. Central Water and Sewage Authority, St. Vincent and the Grenadines tel: (784) 456-2946 fax: (784) 456-552 E-mail:
[email protected]
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
Appendix 1 Inspection Form Manhole
Owner
Inspection date/time
Manhole No
Station
Sewershed.
Plan I.D.:
G E N E R A L
C O V E R
Status:
1
Surface inspected
Location:
3
Internal
Type:
Sidewalk
4
Not found
5
Buried
1
2 3 4
4
Not inspected
5
Fit
Pick
Curb
9
Non-Paved
10
Creek Bottom
Condition:
Tight
3
1 2
3
Loose
4
Bolted
Storm
Good
2
Gasketed
6
Yard-Side
4
Rocking
5
1 3-4 Lane 2
Yard-Front
1
Concealed
Vent
8
Two –lane
Traffic:
Driveway
6
5
Yard-Back
7
Paved Asphalt
2
2
3
Paved
1
3
Highway
4
Parking
5
Alley
6
Driveway
7
Other
No. of
Good
holes
No gasket No bolts
2
Pick 1 Pick 2
Corroded/Pitted
4
3-5
Cracked
Ponding depth (ins)
None
3
5 None
1
5
6-8
6
>8
Cover type
Drainage area x
=
F R A M E
Size (in)
Condition: Depth
Open’g
Cover depth
1 2
3
Frame depth
4
Good Minor Fair Poor
5 Deteriorated
F R A M E S E A L
Observed Inflow (gpm)
Condition:
1 2
3 4
Good
Inflow:
Minor
1 2
3
Fair
4
Poor
5
None Low Moderate Heavy
5 Deteriorated
Severe
267
Manhole Rehabilitation Strategies: A Cost Effective Analysis
B E N C H
Const:
Condition:
None
1
Good
1
2
Minor
2
Pre-cast
2 3
1
Infiltration:
3 4
Brick
3
Fair
4
Poor
5
5
4
Pored
6
Other
Moderate Heavy Severe
Block
5
None Low
Deteriorated Observed Inflow (gpm)
C H A N N E L
Const:
1
2 3 4
None
Condition:
Pre-cast
1
2
3 Poured
4
VCP
5
Plasti
6
Other
Infiltration:
Good Minor
1
None
2
Low
3
Fair
Const:
Severe
Deteriorated
1
2
Condition:
None
4 5
1
2
3 Iron
4
Plastic
Good Minor Fair Poor
5
Other
Deteriorated
REMARKS
268
Fair Poor Deteriorated
Bar
3
Minor
5
Observed Inflow (gpm)
S T E P
Good
2
4
Heavy
5
5
1
3
Moderate
4 Poor
Hydraulics:
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Depth (in):
C
Min. Dia: (in)
H I M
Const:
None
1
N Y
Brick
4
C O
Pored
6
Other
3
E
Const:
location:
W A L L
4
Poor
5
Condition:
None
1
3
Brick
2
Cone Surface
5
Pored
6
Other
Defect Quantity:
/
1 2
3
Condition:
1
2
3
3
Brick
4 Block Pored
6
Other
1
1
Defect: 2
3
2
4
Poor
5
Moderate Heavy Severe
4
4
5
Multiple
3
Bottom Dia: (in)
Pre-cast
5
Fair
Observed Inflow (gpm) 1
Good
Infiltration:
1
2
4
Low
3
Deteriorated
Minimun dimensions (in)
2
None
2
4
2
Joint & cone
None
1
5
Wall cone Joint
1
Heavy
Minor
2
4
1
Const:
Moderate
Inflow:
Good
1
Pre-cast
3
Other
3
Fair
Severe
2
Depth (in):
Defect
Low
3
Observed Inflow (gpm)
Flat top
4
None
2
Deteriorated
Eccentric
2
1
5
Concentric
1
N
4
Block
5
Shape:
Minor
2
3
3
Inflow:
Good
1
Pre-cast
2
E
Condition:
Minor
3
Fair
4
Poor
5
None Low Moderate Heavy Severe
5
4
5
Multiple
2
Location:
3
Observed Inflow (gpm)
3
269
Wall joint Top Half Wall joint + Bottom Half
4
Entire depth 5 6
Deteriorated
4
1
Defect
Other
Manhole Rehabilitation Strategies: A Cost Effective Analysis
APPENDIX 2
Table 1 Manhole I/I Flow Schedule (Manhole Inspection and Rehabilitation ASCE Manuals, Reports on Engineering Practice Component Cover*
Frame Seal
No I/I 1 No evidence
0.0 No evidence
Minor I/I 2 Pick or other unsealed cover (1hole) No Ponding 0.2 Water marks
Rating/Description/Default flow (gpm) Moderate I/I Heavy I/I 3 4 Ponding <1” with pick or Corroded bearing surface unsealed cover No Ponding (5-8 holes) (2-5) holes 0.4 Some soil present at cracks
Severe I/I 5 Ponding >2” pick or other unsealed cover (>8 holes)
0.8 ³ 1.6 Heavy soil/roots/1/8” gap in ³1/8” gap in drainage area drainage area Chimney 0.0 0.2 0.4 0.8 ³ 1.6 No evidence Water Marks Water marks 2-3 Locations or Multi water marks or mineral Multi water marks mineral deposits 1 location mineral deposits deposits Drainage area Joint leak (<10%) Joint leak (<25%) Joint leak (>25%) 0.4 0.4 Cone 0.0 0.2 ³ 1.6 Multi water marks or mineral Water marks 3-4 Locations or No evidence Water marks Multi water Marks Mineral deposits mineral deposits 1-2 locations deposits or soil present Joint leak (25%) Joint leak (10%) Joint leak (>25%) 0.2 0.4 Wall 0.0 0.2 ³0.8 Water marks 3-4 Locations or Multi water marks or mineral No evidence Water marks Multi water Marks mineral deposits deposits 1-2 locations Mineral deposits or soil present Joint leak (10%) Joint leak (25%) Joint leak ( >25%) Pipe Seal 0.0 0.2 0.2 0.4 ³0.8 No evidence Water marks Water marks 3-4 Locations or Multi water marks or mineral Multi water Marks 1-2 locations mineral deposits deposits Mineral deposits or soil present Seal leak (10%) Seal leak (25%) Seal leak ( >25%) 0.4 0.2 Bench 0.0 0.2 ³0.8 Multi water marks or mineral Water marks 3-4 Locations or No evidence Water marks Multi water Marks deposits mineral deposits 1-2 locations Mineral deposits or soil present Joint leak (25%) Joint leak (10%) Joint leak ( >25%) 0.2 0.2 Channel 0.0 0.2 ³0.8 Water marks mineral deposits. Water marks mineral deposits No evidence Water marks Mineral deposits. Soil Or 1/8” crack below flow Or 1/8” crack below flow 1-2 locations or 1/4” crack below flow Note: “% refers to the percentage of circumference that contains the indicated observation.*No default cover inflow provided since inflow depends on type of cover, condition of cover, and ponding depth. Leakage may be calculated using orifice equations.
270
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Table 2 Manhole Structural Rating Schedule (Table 5-2 Manhole Inspection and Rehabilitation ASCE Manuals and Reports on Engineering Practice No. 92) Condition Cover fit Cover condition Frame
1 Good Good Good
Frame seal
Good
Rating/Description 3 Tight Loose No gasket No bolts Chipped/corroded Cracked pitted Cracked (1/6”) Cracked 1/8” or misaligned(>3”) Cracked mortar Missing mortar Hairline cracks Cracks (1/6”) Chipped any 2
4 Rocking Corroded/Pitted Broken(missing pieces) Cracked (1/4)”w/open joint Missing bricks Cracks (¼”) Chipped (10%) 10% of wall profile
Chimney
Brick Precast/Poured
Sound Good
Wall
Brick
Good
Cracked mortar
Missing mortar
Missing bricks
Precast/Poured
Good
Hairline cracks
Chipped any
Cracks (¼”) Chipped (10%) 10% of wall profile
Brick
Good
Cracked mortar
Missing mortar
Missing bricks/Grout
Precast/Poured
Good
Hairline cracks
Brick
Good
Cracked mortar
Cracks (1/6”) Chipped any Missing mortar
Cracks (¼”) Chipped (10%) Missing bricks/Grout
Precast/Poured
Good
Hairline cracks
Brick
Good
Cracked mortar
Cracks (1/6”) Chipped any Missing mortar
Cracks (¼”) Chipped (10%) Missing bricks/Grout
Precast/Poured
Good
Hairline cracks
Good New
Slight corrosion/chip serviceable
Cracks (1/6”) Chipped any Corrosion (26%) Unserviceable
Cracks (¼”) Chipped (10%) Broken or missing step Corrosion (50%) Unserviceable
Pipe seal
Bench
Channel
Steps
Note: “ % refers to the percentage of circumference that contains the indicated observation
271
5 None Cracked/deteriorated Deteriorated (combination of 2,3,4) Deteriorated Deteriorated Voids Cracks pieces missing exposed reinforcing 1”x1” 20% or more of wall thickness lost Deteriorated Cracks pieces missing exposed reinforcing 1”x1” 20% or more of wall thickness lost Exposed soil missing bricks, none Cracks pieces missing, exposed soil, none Exposed soil missing bricks, none Cracks pieces missing, exposed soil, none Exposed soil missing bricks, none Cracks pieces missing, exposed soil, none Deteriorated/hazardous unserviceable
Manhole Rehabilitation Strategies: A Cost Effective Analysis
The cover’s contribution to I/I is not given in Table 2.4 but is estimated from the equation for a circular orifice. Equation 2.1 (Chow 1984)
Q = C d 2 gh A Where, Q – flow rate Cd – orifice co-efficient g – acceleration due to gravity h – ponding depth A – area of hole in cover For an approximate depth of ponding hydraulic engineers at Purdue University were consulted and a depth of 1 inch was suggested. The diameter of the holes in the cover is 1.18 inches. Table 1 shows the approximate inflows from covers based on the number of holes in the cover, and an average ponding depth of 1 inch. Table 1 Relation of flow rate to number of holes in cover No. of Holes in Cover 1 2 3 4 6 8
Flow Rate (GPM) 4.73 9.46 14.19 18.92 28.38 37.84
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Manhole Rehabilitation Strategies: A Cost Effective Analysis
Appendix 2 Results of Manhole Inspection Table 3 Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
3
4
*Frame
2
Frame seal
1
3
4
0.4
Chimney
2
2
4
0.2
Cone
1
2
3
0.2
Wall
2
4
6
0.4
2
Bench
NV
Channel
NV
* Step
9.46
4
4
Pipe seal
NV Total Estimated I/I
10.66
Table 4 Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
3
4
*Frame
2
Frame seal
1
3
4
0.4
Chimney
2
2
4
0.2
Cone
1
2
3
0.2
Wall
2
4
6
0.4
2
Bench
NV
Channel
NV
* Step
9.46
4
4
Pipe seal
NV Total Estimated I/I
273
10.66
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
*Frame
1
3
Frame seal
4
9.46
5
0.4
Chimney
3
4
7
0.8
Cone
3
4
7
0.8
Wall
4
4
8
0.4
Bench
NV
Channel
NV
* Step
2
Pipe seal
NV Total Estimated I/I
11.86
Table 5 Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
2
3
9.46
*Frame
4
Frame seal
1
3
4
0.4
Chimney
2
5
7
1.6
Cone
3
4
7
0.8
Wall
3
4
7
0.4
4
Bench
NV
Channel
NV
* Step Pipe seal Total Estimated I/I
274
12.66
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Table 6 Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
4
5
*Frame
2
Frame seal
2
2
4
0.2
Chimney
3
4
7
0.8
Cone
3
3
6
0.4
Wall
4
4
8
0.4
2
Bench
NV
Channel
NV
* Step
18.92
4
4
Pipe seal
4
4
Total Estimated I/I
0.4 21.12
Table 7 Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
2
2
*Frame
2
2
Frame seal
2
3
5
0.4
Chimney
4
4
8
0.8
Cone
3
3
6
0.4
Wall
3
3
6
0.2
Bench
Not visible
Channel
Not visible
* Step
Not visible
37.84
Pipe seal Total Estimated I/I
275
39.64
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
6
7
*Frame
2
Frame seal
1
2
3
0.2
Chimney
3
1
4
0.0
Cone
1
1
2
0.0
Wall
3
1
4
0.0
2
Bench
NV
Channel
NV
* Step
37.84
4
4
Pipe seal
NV Total Estimated I/I
38.04
Manhole
Structural
I/I
Combined
Estimated
Component
Rating
Rating
Rating
I/I (gpm)
Cover
1
4
5
37.84
*Frame
3
Frame seal
3
1
4
0.0
Chimney
1
2
3
0.2
Cone
1
1
2
0.0
Wall
1
3
4
0.2
Bench
1
1
2
0.0
Channel
1
1
2
*Steps
4
3
4
Pipe seal
Total Estimated I/I 38.24
276
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Table 8 Manhole
Structural
I/I
Combined
Estimated I/I
Component
Rating
Rating
Rating
(gpm)
Cover
4
3
7
9.46
*Frame
2
Frame seal
2
2
4
0.2
Chimney
1
2
3
0.2
3
4
7
0.4
Cone Wall Bench
NV
Channel
NV
*Steps
none
none
none
Pipe seal Total Estimated I/I 10.26
Table 9 Manhole
Structural
I/I
Combined
Estimated I/I
Component
Rating
Rating
Rating
(gpm)
Cover
4
2
*Frame
2
Frame seal
2
2
4
0.2
Chimney
2
3
5
0.4
2
2
4
0.2
4.73
Cone Wall Bench
NV
Channel
NV
*Steps
4
Pipe seal
NV Total Estimated I/I
277
5.53
Manhole Rehabilitation Strategies: A Cost Effective Analysis
Table 10 Manhole
Structural
I/I
Combined
Estimated I/I
Component
Rating
Rating
Rating
(gpm)
Cover
1
6
7
37.84
*Frame
2
Frame seal
2
2
4
0.2
Chimney
2
3
5
0.4
3
3
6
0.4
2
Cone Wall Bench
NV
Channel
NV
*Steps
4
4
Pipe seal
NV Total Estimated I/I 38.94
Table 11 Manhole
Structural
I/I
Combined
Estimated I/I
Component
Rating
Rating
Rating
(gpm)
Cover
1
3
4
9.46
*Frame
2
Frame seal
2
3
5
0.4
Chimney
3
3
6
0.4
Cone
3
3
6
0.4
Wall
4
4
4
0.4
Bench
NV
Channel
NV
*Steps
5
4
Pipe seal
NV Total Estimated I/I 11.06
278
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance by B J Lloyd*, K Guganesharajah# and C A Vorkas* * Centre for Environmental Health Engineering, University of Surrey, UK # Mott MacDonald Ltd, Cambridge, UK Abstract An intensive diagnostic methodology for waste stabilization ponds (WSPs) is described. The methodology addresses both the identification of design and performance deficiencies influencing pathogen removal and the rehabilitation of systems to meet WHO/PAHO guidelines for effluent reuse. The diagnostic commences with a pre-diagnostic and engineering survey followed by the application of field monitoring techniques including onsite continuous logging of key climatic factors and physico-chemical quality parameters. The field monitoring also includes bacteriological testing, microbial tracing, determination of hydraulic retention times and short-circuiting. A dedicated three dimensional computational fluid dynamic (CFD) and integral water quality model (HYDRO 3-D) has been developed and exhaustively calibrated to simulate observed field data from the diagnostic studies. The model features special algorithms to simulate the conditions encountered in WSPs and the techniques used in the model are distinct from the conventional CFD codes. HYDRO 3-D has been used successfully to predict and design the optimal configuration of WSPs to maximize pathogen removal in the Caribbean region. Keywords Bacteriophage hydraulic tracers; diagnostic evaluation; engineering intervention; Finite Integral Method; numerical modelling; pathogen indicator removal; waste stabilization ponds. Introduction Waste stabilisation ponds (WSPs) are a cost-effective means of providing treatment of sewage and with the potential for reducing the health risks associated with massive environmental pollution by excreta-related pathogens and parasites. Guidelines for the safe use of wastewater and excreta in agriculture and aquaculture have been published by WHO (1989) and Mara & Cairncross (1989). However many pond systems do not operate efficiently for pathogen removal, and few epidemiological studies have been undertaken to evaluate the effects of exposure to effluent reuse. Some studies suggest high entero-parasite carriage among agricultural workers associated with WSP reuse schemes (CEPIS/PAHO, 1982) and helminth and cholera transmission in the general public was reported by Shuval et al (1986). The overriding WSP control factors upon which other factors and hence pathogen removal performance ultimately depend, are hydraulic retention time and temperature (Feachem et al., 1983). It follows that whatever factors most influence retention time will most enhance or 279
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
depress pathogen performance. Retention time, in days, is often cited without indicating whether this is nominal or real hydraulic retention time. This is very misleading, given the dependence on treatment in open ponds where hydraulic short-circuiting is almost inevitable. Real hydraulic retention time is controlled by many physical factors including the number of ponds, their dimensions, dead zones, inlet-outlet arrangements, baffling, overall configuration of system, temperature, flow velocities, the earth’s rotation (in large ponds) and wind. Marais (1974) observed an inverse relationship between coliform densities and wind in open pond systems, and Ellis, (1983) concluded incorrectly that “anything that can be done to maximize the effect of wind must be done”. Although prevailing wind direction and speed are recognized as key determinants in controlling efficiency only rules of thumb have been given “to facilitate wind-induced mixing of the pond surface layers, the pond should be located so that its longest dimension lies in the direction of the prevailing wind” (Mara et al., 1992). Thus wind effects are poorly understood and analysis has not been taken into consideration in the design and operation of WSPs. However both moderate and strong winds can be extremely damaging to hydraulic retention time and hence pathogen removal and die-off (Frederick and Lloyd, 1996; Vorkas and Lloyd, 2000b; Lloyd and Frederick, 2000; Lloyd et al., 2002, in preparation). Wsp Monitoring & Evaluation Mara and Pearson (1998) comment that ‘a full evaluation of the performance of a WSP system is a time-consuming and expensive process, and it requires experienced personnel to interpret the data obtained. However, it is the only means by which pond designs can be optimized for local conditions. It is therefore a highly-cost effective exercise’. Protocols were proposed for the minimum evaluation of WSPs at three levels of complexity Pearson at al., (1987a). Frederick (1995) followed the more advanced level 2 monitoring protocol during the course of a prolonged monitoring program by the Water Authority Cayman. This demonstrated that the microbiological performance of facultative and maturation ponds were consistently performing 1-2 log10 below the thermotolerant (faecal) coliform design specification (Frederick, 1995), and failing to meet WHO reuse guidelines. Level 2 monitoring did not permit the identification of the causes of under performance which were therefore investigated using the more advanced level 3 protocol and a variety of additional, intensive field investigations (Frederick and Lloyd, 1996). The supplementary field investigations applied to the Grand Cayman WSP included a bacteriophage tracer study, bathymetric sludge surveys in facultative and maturation ponds and meteorological monitoring. The tracer study demonstrated that retention time in one facultative pond was 85% less than the design retention time. In-pond grid sampling of the tracer in conjunction with the sludge surveys identified defects in the inlets arrangements, short-circuiting paths, and dead zones (Frederick and Lloyd, 1996). Short-circuiting depended on wind speed and direction, as well as pond topography and loading. Operational flow characteristics and engineering design features for the system under study were fed into an uncalibrated three dimensional computational fluid dynamic (CFD) model and, in preliminary studies, confirmed the reduced hydraulic retention time (Fares & Lloyd, 1995) but could not accurately predict the impact of wind variations. Subsequently, using data from the WSP diagnostics described in this paper, Guganesharajah, (2001) calibrated an
280
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
advanced CFD model (HYDRO-3D) to study hydraulic performance taking into consideration the prevailing wind, varying direction and speed, and inlet/outlet arrangements in different configurations. The combination of diagnostic evaluation and HYDRO-3D has confirmed the importance of wind and is now being used to define the optimal pond configuration and inlet/outlet arrangements required to maximize retention time and hence performance. Justification & Aims A number of fundamental factors controlling sewage circulation paths, mixing, dispersion, and hence hydraulic retention time and effluent age structure, may often be the main cause of poor performance in WSP systems particularly lowering pathogen removal (Lloyd and Fredrick, 2000). Hydraulic short-circuiting is a neglected area of performance evaluation but may be amongst the most important reasons why WSPs do not meet design performance specifications. There are relatively few publications which have used tracer studies to identify hydraulic inadequacies in WSPs and, as far as we are aware none, prior to Frederick (1995), Frederick and Lloyd (1996), Torres et al. (1997) and Vorkas and Lloyd (2000b), that have used in-pond grid sampling to identify surface and sub-surface short-circuiting paths. To improve hydraulic efficiency and achieve maximum hydraulic retention time a rigorous methodology for the evaluation and prediction of the impact of proposed engineering upgrades on treatment plant performance is required prior to committing to those engineering interventions. Intensive field evaluations are both time-consuming and expensive and every system is different. However, by conducting such studies, data sets are made available to calibrate hydraulic models such as HYDRO-3D which then become reliable generic design tools. The purpose of this paper is two-fold: a) to describe the main components of the evaluation methodology which have been field tested in the Caribbean and Latin America (Frederick and Lloyd, 1996, Vorkas and Lloyd, 2000b), and b) to demonstrate how HYDRO-3D is calibrated and used to design the most efficient and cost-effective configuration of WSPs in order to achieve higher pathogen removal and meet effluent standards. Diagnostic Methodology A step-wise evaluation methodology is presented in Figure 1 and the practical details for each step are described below. 1: System selection The choice of treatment plants for evaluation will depend on local priorities and in particular the importance attributed to perceived health risks associated with effluent discharge and/or reuse (WHO, 1989). However during the developmental stage of this methodology two important practical considerations which emerged were the logistics of travelling between the plant and/or on-site basic laboratory.
281
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
2: Preliminary diagnostic The purpose of the preliminary diagnostic is to assemble all relevant existing information in order to assess the operation and performance of the selected plant in the light of national or local standards for effluent discharge or re-use. The preliminary diagnostic includes the following elements: a) review of available consulting engineering drawings and reports describing the design and engineering specifications for the WSP system b) acquisition of recent meteorological and geographic data c) review of existing WSP monitoring data d) WSP site visit to verify key characteristics and complete a pre-diagnostic form, e) report summarizing the key deficiencies and potential problem areas identified using the data in a) – d). Findings: from the preliminary diagnostic typically include: · Microbiological results on final effluents not available · Microbiological results on final effluents are substantially worse than WHO guidelines · WSP not built to engineering specification · Flow exceeds design capacity · No inlet or outlet flow measurement devices in operation so no flow data available · Inlet/outlet locations inappropriate · No data available on routine performance monitoring. · No local meteorological data
282
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
1: System Selection
2: Preliminary Diagnostic
Acceptable performance
Unacceptable performance 3: Intensive Field Evaluation
4: Results and Analysis
Unacceptable performance
Acceptable performance 4a: HYDRO-3D CFD Model Analysis
5: Design changes & recommendations Meeting standards or WHO guidelines
6: Engineering Interventions
Figure 1: Outline waste stabilization pond evaluation methodology 3: Intensive field evaluation. Depending on the report and results of the pre-diagnostic, and particularly whether the pathogen indicator results fail to comply with national standards or WHO guidelines, an agreement is drawn up with the local wastewater authority to undertake the intensive field evaluation which involves the following components.
3.1. Flow monitoring. If they are not already present it will be necessary to install appropriate flow measuring devices, at least at the works inlet and outlet, at the start of the evaluation. For smaller works 60o V-notches have sufficed between ponds, but not as inlet structures as they encourage surface short-circuiting. 3.2. Meteorological data; logging of wind speed and direction. At the start of each evaluation a portable meteorological station powered by a 12-14 volt battery was set up. The essential information is wind speed and direction which was logged every 10 seconds and averaged in 10 minute intervals using an automated wind speed field kit (ELE DA800, or Casella). The ELE DA800 portable meteorological station provided continuous monitoring of (i) wind speed (m/s); (ii) wind direction; (iii) wind run; (iv) prevailing wind direction; (v) maximum speed; (vi) time at which maximum wind speed occurred. The recommended ELE software for display of wind roses and data manipulation is MET 250/810. 3.3. Pond sludge surveys. The white towel method described by Malan (1964) was used. To obtain more precise information concerning pond bathymetry, the procedures for measuring the sludge in anaerobic, facultative and maturation ponds, and safety precautions were based
283
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
on information provided by Frederick (1995). Briefly, the dimensions of the facultative pond were checked and compared with the design drawings and confirmed. Sufficient bamboo stakes were prepared to go around the perimeter of the pond to mark an imaginary grid for measurement intervals. As an example: a facultative pond measuring 88 m x 40 m is divided into a grid in which each square was 8 m x 8 m and each intersection off-shore provided for 40 measurement points of sludge depth in the pond. A diagrammatic sketch of the pond was prepared showing the grid and location of inlet and outlet structures, and sludge and water depth data recorded on the grid. The data were entered into an EXCEL spreadsheet for analysis of pond volume, identification of dead zones and topographic display using Surfer software, and subsequent modelling using the computational fluid dynamics model, HYDRO-3D. 3.4. Preliminary orange tracer studies. A similar grid, as for the sludge survey, was prepared for the ponds to be studied using tracers, except that a smaller number of squares is used to sample for the tracer due to the amount of work involved in the analysis. A preliminary study using citrus fruit was carried out to identify surface flow patterns in selected ponds and to provide an indication of retention time. Oranges, and in Colombia Swinglia, a hedging plant around WSPs, were used as they float >98% submerged. Typically 100 fruits of similar size were injected at the inlet of the selected ponds and their location in the pond was monitored at measured time intervals until the majority had arrived at the pond outlet. Their location was plotted on multiple photo-copies of an accurate sketch of the grid. Surface dispersion and tracking of the fruit was subsequently correlated with wind speed and direction abstracted from the ELE wind logger (Vorkas and Lloyd, 2000 b). 3.5. Physico-chemical monitoring wastewater quality data logging. Field testing was carriedout using three Grant-YSI Model 3800 water quality loggers powered by 9 volt batteries. These provided continuous data logging for up to three days after which recalibration was necessary. The following parameters were recorded in the raw sewage, the outlet of the primary pond, secondary and the tertiary final effluent: (i) dissolved oxygen (DO) profile; (ii) pH variations; (iii) temperature; (iv) ammonia-nitrogen (NH3-N) or (v) nitrate; (vi) salinity/conductivity; (vii) turbidity. Data were downloaded, using Squirrel or Lotus software, to EXCEL spread sheets for subsequent analysis. 3.6 Routine microbiological examination. Analysis for thermotolerant (faecal) coliforms at 44oC was performed before and after each treatment stage throughout a 3-4 week study period. Decimal dilution series, membrane filtration and Oxoid standard ISO formulation thermotolerant (faecal) coliform culture media were used. The OXFAM-DelAgua water test kit with a battery operated incubator was used to guard against local power failures. 3.7 Microbiological tracer studies. The hydraulic behaviour of ponds was investigated using bacteriophages as tracers. They are host specific and are the most sensitive tracers as they can be detected at extremely low (10-10) dilutions (Vorkas and Lloyd, 2000a). Five bacteriophage strains were validated for field use using the following host cultures and their corresponding phages; Serratia marcescens phage (NCIMB 10644), Erwinia ananas (ATCC 8366), Erwinia amylovora (ATCC 29780 and ATCC 19382) and Pseudomonas phaseolicola
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A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
host strain (NCIMB 11266). They are conveniently produced in one litre quantities and stored until required, without loss of viability, at –70oC The phage suspensions are transported to the field in cool boxes with ice packs. Preliminary calculations should be made from the pre-diagnostic information to ensure that an adequate concentration is added to the WSP. After complete mixing a useful concentration is in the range 103 – 107 ml-1. As an example, a concentration of 5 x 103 ml-1 may be obtained, when completely mixed, for a small pond of 1000 m3 by adding five litres of phage with a titre of 109 ml-1. With experience, much higher phage titres can be obtained, and therefore as shown in the table a pond with a total volume of 100,000 m3 can still require a dose of only 5 litres providing that a titre of 5 x 1011 ml-1 has been achieved. It is therefore important to titrate phage stock the night before dosing in order to check the titre, and hence the dose, before adding it to the pond. 3.8. In-pond sampling strategy. For in-pond sampling purposes, as for the citrus surface tracer study, ponds are divided into an imaginary grid marked by bamboo posts on the banks. Typically grids split the pond lengthwise into two halves and then each half into 5 sections so that the pond comprises of 10 equal areas (see above 3.3 and 3.4). If it is clear from preliminary observations and measurements that early stages of treatment, typically anaerobic ponds, are overloaded and require desludging, there is little point in carrying out tracer studies on them and the effort may be more usefully allocated to facultative and maturation ponds. This was the case in the example shown below and therefore the modelling example focuses on a facultative pond. Results 4: Analysis and Numerical Modelling with HYDRO-3D Studies on facultative and maturation ponds in Grand Cayman (Frederick & Lloyd,1996), Colombia (Vorkas & Lloyd, 2000) and in Mexico (in preparation) have highlighted the shortcomings of the conventional Marais (1974) design procedure. They showed that the measured retention time was far below the nominal retention time. More recent studies have assessed the applicability of three-dimensional hydraulic and water quality models for designing WSPs (Guganesharajah, 2001). Extensive research has been carried out at the University of Surrey over the last two years to develop the HYDRO-3D model for specific application to WSPs. The current version of the model has options to simulate the wind induced currents, define inlet and outlet flows and to model contaminants as shown below. 4.1 Modelling Waste Stabilisation Ponds. Three-dimensional computational hydraulic models are based on the Reynolds equations, which are derived from the Navier-Stokes equations by considering the mean and fluctuating components of velocities. HYDRO-3D employs the Reynolds equations with stresses represented by the Boussinesq hypothesis. The numerical procedure used in HYDRO-3D is the Finite Integral Method (FIM), which differs from the conventional Finite Element, Finite Volume or Finite Difference techniques. FIM is a new technique evolved at the University of Surrey, under a research project investigating procedures to maximise the retention time in waste stabilisation ponds. FIM uses interpolation functions together with the nodal parameters to define a global function for 285
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
variables within a model region. The variables can be either hydraulic or water quality parameters. The global function is integrated over a control volume to derive the numerical equations, which are solved with the boundary conditions to obtain the unknown nodal values (Guganesharajah, 2001). 4.2 Model example; the Ginebra WSP System. Modelling the wind generated currents and the circulations induced by inlets and outlets to a satisfactory level of accuracy is crucial in any modelling exercise. The WSP investigated is situated in Ginebra (near Cali), Colombia. The sewage treatment plant serves the town of Ginebra with a population of 5,900. The pond system is comprised of an anaerobic pond, a facultative pond and a maturation pond (Figure 2). 112m
Anaerobic Facultative Pond
Inlet
56 m
Maturation Pond Outlet
Figure 2: Outline sketch of Ginebra WSP configuration and flow path.
N
The modelling study was focused on the facultative pond, which is orientated 315 degrees N. The pond is 56 m wide, 112 m long and has an average depth of 1.8 m. 4.3 Data Collection. Extensive data collection and sampling of bacteriophage was undertaken in December 1997 (Vorkas and Lloyd, 2000). The details of data collected during this period are summarised in Table 1. Table 1: Ginebra WSP Data Collection Data Period of Collection Remarks Wind speed and direction
3 to 14 December 1997
Discharge at outlet
8 AM to 6 PM on 9 December 1997 8 AM on 9 December 1997 to 9 AM on 10 December 1997 10:50 on 8 December 1997 to 14:50 on 9 December 1997.
Bacteriophage sampling Tracking of oranges
Data were logged at 10 minute intervals.from a portable on-site weather station (ELEDA800). The discharges were measured using a V-notch weir installed at the outlet. The data includes measurements at the outlet and in the pond. Eighty (80) oranges were released and the locations of the oranges plotted at different times.
In addition to the above data the bathymetry of the ponds was surveyed. 4.4 Model Network Development. The first stage of the model development is to enter the pond dimensions and discretise the model region to develop the model network. The model network file includes the co-ordinates of nodal points together with their links with model
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A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
elements which are a tetrahedral shape. The plan view of the model network set up for the facultative pond of Ginebra WSP is shown in Figure 3, which has been produced using the ArcView pre-processing facilities available in the HYDRO-3D model (Guganesharajah, 2001).
Outlet (0.375 m Pipe)
N 112 m
Inlet (0.375 m Pipe)
56 m
Figure 3: Plan View of Model Network of Ginebra Facultative WSP The pond depth is represented as four equally spaced layers (Faces) in the model network with a total of 5,510 nodes. The pond is divided into 24,192 tetrahedral elements. As shown in Figure 3, a higher resolution of 1m (base length and height of the triangle in plan area) is used for a length of 4 m at the upstream (inlet) and downstream (outlet) end of the pond. For the remaining area a resolution of 4 m is used. The higher resolution is necessary to accurately model the circulation generated in the vicinity of the inlet and the outlet. The nodal points of the bottom (Face 4) of the model are defined using the bathymetric survey data of the pond bed (Vorkas and Lloyd, 2000b). 4.5 Calibration of Hydraulic Model for the Ginebra Facultative Pond. The inlet and outlet discharges and climatic data are required to run the model. The influent enters the facultative pond via a 0.375 m diameter pipe, which is positioned 0.8 m from the bottom of the pond and 3 m from the southern edge of the wall. The average inflow to the facultative pond is 21 l/s, which is consistent with the measured outflow. The outlet weir extends 1 m from the north wall. The positions of the inlet, outlet, discharges and area of pipes have been included in the model. The wind speed and direction data, averaged at 10 minute intervals using the portable weather station, were entered into the model. In order to minimize the errors in using averaged values with large time intervals, model runs have been undertaken at 10 minute intervals. The model was run for a period of 4 days using the observed wind data from 6 AM on 8th December 1997 to 10th December 1997. Initial hydraulic conditions of zero velocity and constant water level in the pond (this condition is generally referred to as ‘cold start’) were used in the model. Test runs on the model for periods varying from 2 to 12 hours indicated that a minimum period of 2 hours is sufficient to bring the model to a dynamic condition. In this context the results at hour twelve is the same irrespective of whether the model is run from hour one (1) or hour ten (10) with a ‘cold start’. 287
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
The hydraulic model was calibrated using the observed positions of floats (oranges) for the period 8th to 9th December 1997 (Vorkas and Lloyd, 2000b). A sample of observed and simulated position of floats are shown in Figure 4.
Wind direction
Observed: 8/12/97 16:00
Simulated: 8/12/97 16:00
Principal flow path
Figure 4: Observed and Simulated Positions of eighty Floats It should be noted that the model assumes that the measured wind speed is the same throughout the pond. This assumption is not strictly valid in the vicinity of walls where the wall has some influence on the wind pattern. The wind speeds used in the model are the average values for each time step of 10 minute interval. The influence of gusts or other localized effects can have a significant influence on the positions of oranges. The observations indicated that the oranges are clustered together in several locations. The free movement of a single orange is different to the movement of clustered oranges. However the simulated positions of oranges generally conform to the wind directions and the positions are comparable with the observed data. 4.6 Calibration of Water Quality Model - Ginebra Facultative Pond. The calibration of the water quality model was based on the tracer experiments carried out at the site by Vorkas and Lloyd (2000). In this experiment bacteriophage (Serratia marcescens) was injected at the inlet and measurements of concentration were taken within the pond and at the outlet. The phage was released at 9:00 AM on 9th December 1997 and measurements were taken over four days. The quantity of phage released at the inlet contained a total of 1.778 ´ 1014 phages. In-pond phage measurements were taken at 2, 5.5, 24, 30, 48, 75 and 96 hours after the release of phage at the inlet. The measurements at the outlet were also taken at frequent intervals over a four day period. The phage levels simulated by HYDRO-3D for time step 2 hours for Face 1 (pond surface) and Face 2 (30 cm below the surface) are shown in Figure 5. It is important to note that the leading edge in Face 1 is more advanced than in Face 2 emphasizing the much higher flow velocities, and hence short-circuiting, at the surface.
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A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
leading edge in Face 1 is more advanced than in Face 2 emphasizing the much higher flow velocities, and hence short-circuiting, at the surface. N
1.0
2.0
1.0
2.0
4.13
21.1
4.1
21.1
277
23.5
Wind direction
Distance( m)
Distance ( m)
1.00
30.0
11.0
30.0
23.5
277
Distance ( m)
Distance ( m)
Face 2
Face 1 Observed phage counts (1000/ml) Simulated phage contours (1000/ml)
5.00
Figure 5: Observed and Simulated Phage Levels Figure 5 shows the simulated and observed phage counts in the system at various locations. The simulated results are comparable with the observed data in the downstream area. One observed count of 277,000 counts/l observed (shown ringed in red) in the system is 25 m away from the location of the simulated peak, which is about 220 000 counts/l, otherwise the agreement of observed and simulated phage levels is satisfactory. The observed levels are given for the surface and for a layer approximately 0.3 m below the top surface. The results are presented in this form because the samples were collected at depths of 0.15 to 0.30 m. 14
Phage Counts (1000/ml)
12 10 8
Sim ulated
6
O bserved
4 2 0
0
20
40
60
80
T ime (hours)
100
120
Figure 6: Observed and Simulated Phage Level at the Outlet 289
A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
The simulated and observed phage levels at the outlet of the facultative pond are shown in Figure 6. The simulated peak matched well with the observed peak at 5 hours. There is a sharp drop in phage level after 5 hours, which is mainly due to the peak concentration being recirculated in the pond and mixed before passing through the outlet. The simulated profile generally conforms well with the observed data. The anomalies between 5 hours and 20 hours can be rectified by including the wind effects in the vicinity of the wall, which can not be measured and extending the finer resolution of the model grid further upstream of the outlet. However the calibration is satisfactory for engineering purposes since the mean hydraulic retention time calculated from the tracer study was 1.38 days and the simulated value is very close to this. By contrast the nominal retention time calculated from the pond volume/flow (V/Q), which is normally used for design purposes, is 6 days! This emphasizes the very substantial errors implicit in using the nominal retention time and the value of using a calibrated model. 5: Interventions and HYDRO-3D Model Applications. HYDRO-3D has been calibrated to the point where it can now used to design WSPs and to identify the best options for improving an existing WSP. The model is currently being applied to maximize the retention time of a WSP system in Mexico. The options include the orientation and partitioning of the ponds and sizing of the openings connecting a partitioned channel system. A similar study is being undertaken in Lidsey, UK to maximize the retention time of tertiary pond channels, which receives effluents from treatment works. Space is not available here to demonstrate the range of applications, but a flow diagram and manual are available from the authors which outlines the procedures and decisions to be made in applying HYDRO-3D to WSPs. Discussion and Conclusions The field evaluation procedures described in this paper have been successfully applied to a number of systems in Latin America and the Caribbean. One application has been carried through to the post-intervention stage resulting in major improvements in pathogen indicator removal. The improvement in maturation pond performance was directly attributed to the reduction of hydraulic short-circuiting and reduction in wind effects (Lloyd, Vorkas & Guganesharajah, 2001 in preparation). The most important requirement of any WSP system for pathogen removal performance efficiency is to maximize hydraulic retention time. The results of the pre-diagnostic and intensive field evaluation method described here may sometimes provide sufficient evidence on which to base engineering interventions. However a fully calibrated CFD model, HYDRO-3D, will now begin to provide a more scientifically rigorous and efficient basis for site specific WSP design and performance improvement strategies. Acknowledgement This project is supported by the U.K. Department for International Development (DFID) under research contract No. R7878. We gratefully acknowledge the support of DFID,
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A Diagnostic Methodology and Computational Model for the Design of Improved Waste Stabilization Pond Performance
however the opinions expressed in this paper should not be taken to reflect the views of DFID. References CEPIS/PAHO (1982) Evaluation of the San Juan stabilisation ponds: research report on the second phase. Panamerican Centre for Sanitary Engineering and Environmental Sciences, Lima, Peru, citing C. Lucas M Sc study on ‘The incidence of intestinal helminths in agricultural workers and students in San Juan de Miraflores’. Curtis,T.P. Mara, D.D. and Silva, S.A. (1992) Influence of pH, oxygen and humic substances on ability of .sunlight to damage faecal coliforms in waste stabilisation pond water. Appl. Environmental Microbiol, 58 (4), 1335-1343. Ellis, K.V. (1983) Stabilisation ponds: design and operation. Critical Reviews in Environmental Control, 13, 69-102. Fares, Y. R. and Lloyd, B.J. (1995) Wind effects on residence time in waste stabilisation ponds, In Proc. 26th .Congress of the International Association of Hydraulic Research (IAHR), Theme 4-D, London, Sept Feachem, R.G., Bradley, D.G., Garelick, H. and Mara, D.D. (1983) Sanitation and disease: Health aspects of excreta and wastewater management. World Bank Studies in Water Supply and Sanitation, Vol 3, John Wiley and Sons, UK. Frederick, G. (1995). The performance of waste stabilisation ponds treating saline wastewater, with particular reference to bacteriophage as a hydraulic tracer. Ph.D. thesis, University of Surrey. Frederick, G.L. and Lloyd, B.J. (1995). Evaluation of Serratia marcescens bacteriophage as a tracer and a model for virus removal in waste stabilisation ponds. Wat. Sci. Tech.3l (12), 291-302. Frederick, G.L. and Lloyd, B.J. (1996). An evaluation of retention time and short-circuiting in waste stabilisation ponds using Serratia marcescens. Wat. Sci. Tech.l 3 (7) 49-56. Guganesharajah, K.R. (2001). Development of computational hydraulic and water quality models for rivers, estuaries, reservoirs and aquifers, with particular reference to waste stabilisation ponds. Ph D thesis, University of Surrey. Lloyd B.J and Fredrick, G.L. (2000). Parasite removal by waste stabilization pond systems and the relationship between concentrations in sewage and prevalence in the community. Water Sci. & Tech. 44 No.10/11, 375-386. Lloyd, B.J.,Vorkas, C.A. and Guganesharajah, K.R. (2002) in preparation. Reducing hydraulic short-circuiting in maturation ponds to maximize pathogen removal using channels and wind breaks. Malan, W.M. (1964). A guide to the use of septic tanks systems in South Africa. C.S.I.R. report No.219. Pretoria, South Africa: National Institute for Water Research. Mara,D.D. and Cairncross, S. (1989) Guidelines for the safe use of wastewater and excreta in agriculture and aquaculture, WHO. Mara, D.D. Alabaster, G.P. Pearson, H.W. and Mills, S.W. (1992) Waste Stabilisation Ponds; a design manual for eastern Africa. Published by Lagoon Technology International, Leeds, England. Mara, D.D. and Pearson, H.W. (1998) Design manual for waste stabilisation ponds in Mediteranean countries Published by Lagoon Technology International for the European Investment Bank. Marais, G.v.R. (1974) Faecal bacterial kinetics in waste stabilisation ponds. J.Env. Eng. Div., Am. Soc. Civ. Eng. 100.(EE1), 119-139.
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Pearson, H.W. Mara, D.D. and Bartone, C.R. (1987a) Guidelines for the minimum evaluation of the performance of full-scale waste stabilisation ponds. Water Research, 21 (9), 10671075. Pearson, H.W. Mara, D.D. Mills, S.W. and Smallman, D.J. (1987 b) Physico-chemical parameters influencing faecal bacterial survival in WSPs. Wat. Sci. Tech, 19 (12), 145-152. Shuval, H.I. Adin, A. Fattal, B. Rawitz, E. and Yekuitel, P. (1986) Wastewater irrigation in developing countries: health effects and technical solutions. World Bank Technical Paper No.51. Torres, J.J. Soler, A. Saez, J. and Ortuno, J.F. (1997) Hydraulic performance of a deep waste water stabilisation pond Wat. Res. 31, (4) 679-688. Vorkas, C.A. and Lloyd, B.J (2000a) A comparative assessment of bacteriophages as tracers and models for virus removal in waste stabilisation ponds. Wat. Sci. Tech. 44 No.10/11, 127138. Vorkas, C.A. and Lloyd, B.J. (2000b). The application of a diagnostic methodology for the evaluation of hydraulic design deficiencies affecting pathogen removal. Wat. Sci. Tech.. 44 No.10/11, 99-109. World Health Organisation (1989). Health guidelines for use of wastewater in agriculture and aquaculture.Technical Report series, 778, WHO, Geneva. Author:
Professor B J Lloyd Director: Centre for Environmental Health Engineering CEHE Dept of Civil Engineering University of Surrey Guildford GU2 5XH Tel: +44 483 259930 Fax: +44 483 450984 www.surrey.ac.uk\CivEng\research\environ\cehe K Guganesharajah Mott MacDonald Ltd, Cambridge, UK C A Vorkas Dept of Civil Engineering University of Surrey Guildford GU2 5XH
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys by James W. Hotchkies, P.Eng. General Manager – Land Development Systems, ZENON Environmental Inc. Abstract By 1998, the municipal wastewater treatment plant (WWTP) in the City of Key Colony Beach, Florida, had reached its rated capacity and was limiting opportunities for development. Furthermore, the City recognized that the existing WWTP would be unable to achieve anticipated effluent discharge requirements (5 mg/L BOD & TSS, 3 mg/L TN and 1 mg/L TP) without significant modification. In addition, the community wanted to irrigate the local golf course using recycled wastewater. The City retained an engineering firm to design an upgraded sewage treatment facility to achieve the community objectives, without being overly complex to operate or requiring more space than the existing facilities. After careful consideration, the City selected ZENON’s ZenoGem® membrane bioreactor (MBR) process for several reasons: the ability to achieve a high quality, particulate free, effluent on a very compact footprint and the ability to generate an effluent suitable for direct RO treatment without pretreatment (i.e. MBR effluent SDI < 3). The ZenoGem® process was commissioned in June 1999. The downstream RO system was commissioned in December 1999. Since start-up, the ZenoGem® process has treated all flows to the wastewater treatment facility and daily plant monitoring has demonstrated that the effluent quality exceeds existing requirements. The ZenoGem® effluent turbidity has been consistently measured at <0.2 NTU. An intensive sampling program was conducted in the winter of 1999-2000 to verify that the treatment facility can achieve the more stringent 5/5/3/1 effluent requirements. Results from this intense sampling program and routine plant monitoring will be presented. The RO unit has been operated for only intermittent periods because the water distribution system has not yet been constructed. Plant testing indicates an RO permeate TDS of <100 mg/L, which is entirely suitable for the intended irrigation purposes. There has been no evidence of RO membrane fouling, indicating that the ZenoGem® effluent was entirely suitable for direct feed to the RO. Since August 2000, ZENON has used the facility to demonstrate recent improvements to the membrane technology including cycled aeration for energy reduction and an improved module design to reduce membrane cleaning. Key Words Membrane bioreactor, ultrafiltration, wastewater re-use, nitrogen reduction, phosphorus reduction
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
ZeeWeed® - ZenoGem® Process Membrane technology has advanced significantly in the past decade, for both water purification and wastewater treatment. Today, membrane-based systems have become the preferred technology for many potable water purification applications: Cryptosporidium and Giardia control, color or suspended solids removal, etc. Most recently, the combination of membranes with the activated sludge process has redefined basic sewage treatment, optimizing the biological treatment operation and yielding a treated effluent that is ideal for re-use. Two key advances in membrane technology are at the leading edge of this trend: lowpressure, immersed membranes (the ZeeWeed® hollow-fiber membrane) and the integration of biological treatment and membrane separation (the MBR process). Membranes are available in a diverse range of forms and configurations, with membrane pore size, or molecular weight (MW) separation being the primary characteristic of differentiation. Based on this type of differentiation, systems are classified as microfiltration (MF), ultrafiltration (UF) or reverse osmosis (RO). Most integrated membrane bioreactor systems utilise either UF or MF in their processes. UF is capable of separating both insoluble solids in the process fluid (bacteria, most viruses, colloids and suspended solids) as well as higher molecular weight soluble organics. MF is also capable of separating most suspended solids in the process fluid (bacteria, many viruses and other suspended solids). However, neither UF nor MF is a complete barrier to viruses. For that reason, most membrane systems used for water recycle applications, are complemented by a disinfection process. Further, two membrane configurations dominate sanitary wastewater applications: tubular and immersed, hollow-fibre. In a tubular membrane configuration, the membrane material is attached to the inside of a porous support tube which, in turn, is sealed to a concentric, external collection vessel. The tubes are generally from 10 to 25 mm (3/8” to 1”) in diameter, and may be configured as multiple tubes in parallel or in series within a single collection tube. Mixed liquor is pumped from the biological treatment tank to these tube arrays. Concentrate from the process is returned to the activated sludge tank, while permeate is withdrawn for disinfection and discharge. Trans-membrane pressures range from 100 to 450 kPa (15 to 65 psi). ZeeWeed® are proprietary hollow-fibre UF membranes that are immersed within the bioreactor, in direct contact with the mixed liquor. The composite membrane elements are long, flexible and extremely durable, with an inside diameter greater than 0.5 mm. The hollow membranes are “potted” into top and bottom headers, and assembled into a membrane module.
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
ZeeWeed® Hollow-fibre Membrane In the MBR process (ZenoGem®), the ZeeWeed® membrane is immersed directly into the mixed liquor of the biological reactor, reducing the entire treatment process to a single-step operation and replacing the clarifier of a conventional plant with an ultimate barrier for biomass control. Connected through the header system to the suction side of a permeate pump, the membranes are subjected to a slight negative pressure of 20 to 50 kPa (3 to 7 psi). In an “outside-in” process operation, water is drawn from the mixed liquor through the membrane wall and into the capillary. From there, the treated water is drawn through the header and out through the discharge system. On a continuous basis, air is pumped into the bottom header, where it emerges as a coarse bubble stream. This air stream performs the triple role of process aeration, mixing of the biomass and membrane cleaning. Bioreactor
Wastewater Influent
Treated Water
Screening
Clean In Place Tank
Blowers
Mixed liquor Recirculation
Concentrate or sludge
Typical ZenoGem® Membrane Bioreactor System
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
This suction-based technology eliminates the need to pump mixed liquor through the membrane system, significantly reducing the potential for membrane fouling and dramatically lowering energy consumption. Also, with the continuous movement of air bubbles around and through the fibres, a lower concentration of biomass is maintained around the membranes and this, in turn, minimises the potential for membrane fouling. The ZeeWeed® membranes are automatically backpulsed on a regular basis using collected permeate. Supplemental coarse or fine bubble diffuser grids may be used to supply the remainder of the biological oxygen requirements. Sludge is wasted directly from the aeration tank at the operating MLSS concentration between 10,000 – 16,000 mg/L. Prior to the introduction of ZeeWeed® in 1994, the tubular configuration was the optimal choice for handling the large, gelatinous, suspended solids that are inherent to a sanitary, activated sludge, mixed liquor. However, almost all systems are now based on the significantly more energy efficient, immersed, hollow-fibre membrane. The ZeeWeed® membrane exhibits a very large membrane surface area, and operates at only 10% of the energy consumption of tubular configurations. The large surface area in contact with the process fluid allows operation at very low trans-membrane pressures. This, in turn, reduces fouling of the membrane surface and allows for extended periods of operation with very low maintenance. In addition, the loose fibres in the ZeeWeed® configuration minimise the potential for fouling that might be caused by solids entrapment. The performance and efficiency of conventional biological reactor systems is limited by clarifier performance. This is a function of operator skill, sludge settleability, basic clarifier design, solids management, and the extent and rate of variability in hydraulic or organic loading. When upsets occur, solids can be lost and plant performance compromised. In order to maintain adequate settling characteristics, suspended growth activated sludge plants are limited to MLSS concentrations of less than 3,500 mg/L. With membrane separation, however, the normal clarification process is eliminated and replaced by a simple, reliable and positive barrier to all suspended solids and micro-organisms. Separation performance is independent of the quality, or condition of the biological process fluid and the entire treatment process is simplified. Process upset problems, associated with sludge bulking and difficult mixed liquor floc conditions, are eliminated. As a result, a very stable and efficient biological process is maintained. Operating at MLSS levels of up to 16,000 mg/L, membrane bioreactors create a significantly more efficient process environment that enhances organic consumption and reduces sludge production. Most membrane bioreactors operate effectively at short Hydraulic Retention Times (HRT), and are designed to provide long Solids Retention Times (SRT). HRT periods of less than 6 hours and SRT duration in excess of 6 months are not uncommon. With such a low HRT, reactor volumes may be significantly reduced. Also, combining long SRT with high biomass results in a more efficient process for destroying more complex organics, reducing sludge yield and producing a highly stabilised sludge. In many applications, the extremely compact size of the ZenoGem® process allows the entire system to be enclosed in a compact “closed” system. Frequently, the entire system is located inside the commercial or
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
institutional building or facility, close to the source of the wastewater, thereby reducing installation costs. Combining an immersed membrane with a continuously stirred bioreactor offers a number of process advantages that translate into cost-effective treatment and better effluent quality: ü The membranes allow operation of the bioreactor with high MLSS content, providing a high micro-organism to volume ratio. This allows efficient treatment in small bioreactors, and therefore allows existing treatment plants to be upgraded in capacity by up to 500%. ü The effluent from a ZenoGem® process exhibits almost non-detectable TSS levels, independent of the bio-treatment efficiency. Therefore, the effluent is free of protozoa and cysts, and has significantly reduced bacteria and viral counts. ü The ZenoGem® process is ideally suited for phosphorus removal. Through the addition of metal salts, such as alum, to the raw wastewater or mixed liquor, soluble phosphorus in the waste stream can be precipitated. The ZeeWeed® membranes provide an absolute barrier to the discharge of precipitated phosphorus. The phosphorus is retained in the mixed liquor and removed with the waste activated sludge. This translates into reduced alum dosages since the requirement is only to micro-floc the phosphorus to be removed. ü The membrane retains the micro-organisms within the bioreactor at all times, ensuring easy operation, but also ensuring that difficult to settle bacteria such as nitrifying bacteria are retained resulting in high nitrification rates, even in cold weather. ZeeWeed® membranes can be operated effectively at MLSS concentrations up to 16,000 mg/L, three times greater than the maximum recommended MLSS concentration of 5000 mg/L for extended aeration design. The increased mass of biological solids per unit bioreactor volume allows the ZenoGem® process to be operated at reduced organic loading rates and elevated SRT (> 15 days). Year-round nitrification is ensured because the operating SRT greatly exceeds the minimum SRT required for nitrification which is typically 5-7 days under winter operating conditions. ü ZenoGem® bioreactors are ideally suited for denitrification as well. Since the ZeeWeed® membranes eliminate the need for secondary clarification, it is not necessary for the operators to concern themselves over maintaining an easily settleable sludge. The anoxic zone can be sized for optimal nitrogen removal and, with the high MLSS concentrations, total nitrogen removal efficiency of over 90% is readily achieved. ü The effluent levels of BOD, nitrogen, phosphorus and suspended solids are very low, meeting tertiary treatment criteria without the need of additional filters. ü The process allows for sludge digestion within the bioreactor. ü Immersing the membranes in the bioreactor saves on footprint. Typically, the footprint of a ZeeWeed® plant is only 10% that of a tertiary treatment activated sludge plant. ü Being modular, the ZenoGem® process allows for the stepwise expandability of existing treatment plants while generating a high quality effluent. Although the ZenoGem® process operates at high organic loadings, the quality of the effluent remains of high quality and meets surface water discharge criteria.
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
Key Colony Beach WWTP – Process Description The aeration tank at Key Colony is separated into two trains, with each train divided into three distinct zones separated by concrete baffles (Zones 1,2 and 3).
Alum Train 2
Permeate
Influent Wastewater Train 1
Aerobic Zone
Aerated Anoxic Zone
Anoxic Zone
Key Colony Beach WWTP Process Schematic The raw wastewater, after passing through the rotating drum screens, is fed into Zone 1, which has a combined (Train 1 + Train 2) operating volume of 55,500 US gallons. A small amount of air is used for mixing in this zone, but the DO concentration is maintained less than 0.2 mg/L. The majority of denitrification occurs in this zone. The mixed liquor flows by gravity (through a submerged cutout) from Zone 1 to Zone 2. Zone 2 has a combined operating volume of 74,000 US gallons. Zone 2 is aerated at a limited rate to achieve a DO concentration in the range of 0.2 to 0.8 mg/L. The DO in Zone 2 is maintained at a low enough concentration to allow both nitrification and denitrification to occur in Zone 2, minimising the ammonia and nitrate concentration entering Zone 3. The mixed liquor flows by gravity (through a submerged cutout) from Zone 2 to Zone 3. Zone 3 has a combined operating volume of 68,700 US gallons. This zone also contains the ZeeWeed® membranes. This zone is fully aerobic and aerated by a grid of coarse bubble diffusers to achieve a DO concentration greater than 2 mg/L. Any of the remaining ammonia and soluble carbon (BOD5) will be oxidised in this zone. Mixed liquor from Zone 3 is recirculated back to Zone 1 at a flowrate of 1650 US gpm, approximately 4 to 8 times the influent flowrate.
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
Key Colony Beach WWTP – Process Optimisation The Key Colony process was designed to ultimately achieve a high quality effluent with concentrations of: BOD5 < 5 mg/L, TSS < 5 mg/L, TN < 3 mg/L, and TP < 1 mg/L. The membranes alone do an excellent job of separating BOD, TSS, and phosphorus (with chemical addition). In January 2000, ZENON began the optimisation of the process in order to achieve a total nitrogen concentration of less than 3 mg/L. Prior to process optimisation, the dissolved oxygen concentrations in the first two zones were too high to achieve efficient denitrification. Zone 1 was originally designed to be mixed by coarse bubble aeration. In January 2000, the airflow to Zone 2 was cut back significantly and only enough air was allowed through the aerators to keep the tank mixed. In an effort to further optimise performance, mechanical mixers were installed in Zone 1, in August 2000, so that Zone 1 can now be operated without adding more air. The valves to the Zone 2 aerators were manually adjusted to achieve a dissolved oxygen concentration in the range of 0.2 - 0.8 mg/L. The results from a 3-day sampling program, conducted in March 2000, as illustrated below. These results show that during the demonstration period the plant effluent met the criteria of BOD < 5 mg/L, TSS < 5 mg/L, and TN< 3 mg/L. Sample Location
Sample Time
BOD
TSS
Ammonia
TKN
Nitrate
Nitrite
TN
Influent Effluent
3 Day Average 3 Day Average
214 <2
131 < 4.3
31 0.50
39 0.97
< 0.05 1.18
< 0.05 < 0.05
39 2.14
Inluent
Day 1 (avg) Day 2 (avg) Day 3 (avg) Day 1 (avg) Day 2 (avg) Day 3 (avg)
243 170 230 <2 <2 <2
177 153 64 < 4.9 <4 <4
33 31 28 0.55 0.43 0.51
42 40 37 1.30 0.80 0.80
< 0.05 < 0.05 < 0.05 1.27 1.11 1.16
< 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05
42 40 37 2.57 1.91 1.96
3/6/00 2:00 PM 3/6/00 8:00 PM 3/7/00 8:00 AM 3/7/00 2:00 PM 3/7/00 8:00 PM 3/8/00 8:00 AM 3/8/00 2:00 PM 3/8/00 8:00 PM 3/9/00 8:00 AM 3/6/00 2:00 PM 3/6/00 8:00 PM 3/7/00 8:00 AM 3/7/00 2:00 PM 3/7/00 8:00 PM 3/8/00 8:00 AM 3/8/00 2:00 PM 3/8/00 8:00 PM 3/9/00 8:00 AM
320 250 160 170 180 160 130 240 320 <2 <2 <2 <2 <2 <2 <2 <2 <2
160 120 250 170 120 170 110 50 32 <4 4.7 6 <4 <4 <4 <4 <4 <4
17 22 59 18 25 49 15 23 47 1.5 0.12 < 0.02 < 0.02 0.082 1.2 1.4 0.095 0.04
26 30 70 21 33 65 20 24 66 2.4 0.78 0.72 < 0.4 < 0.4 1.6 1.6 < 0.4 < 0.4
< 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 1.4 1.2 1.2 1 0.93 1.4 1.5 1 0.97
< 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05
26 30 70 21 33 65 20 24 66 3.8 1.98 1.92 < 1.45 < 1.38 3 3.1 < 1.45 < 1.42
Effluent
Influent
Effluent
Results from Nitrogen Removal Demonstration at Key Colony (March 2000) (all concentrations given in mg/L)
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
Following the nitrogen removal demonstration, for a period of four weeks, dosage of aluminium sulphate (alum) was initiated at an approximate dosage rate of 60 mg/L in order to demonstrate the ability to produce effluent with < 1 mg/L total phosphorus. Analytical results from this demonstration can be found below. Sample Location
Sample Time
TP
Influent Effluent
Average Average
5.20 0.34
Inluent
03/04/00 04/04/00 05/04/00 17/04/00 18/04/00 19/04/00
5.24 5.17 4.48 5.68 4.76 5.88
Effluent
3/28/00 8:20 PM 3/29/00 8:00 AM 3/29/00 2:00 PM 3/29/00 8:00 PM 3/30/00 8:00 AM 3/30/00 12:00 PM 03/04/00 04/04/00 05/04/00 17/04/00 18/04/00 19/04/00
0.35 0.29 0.33 0.36 0.35 0.38 0.26 0.24 0.31 0.46 0.39 0.38
Results from Phosphorus Removal Demonstration (March-April 2000) (all concentrations given in mg/L) These results indicate that effluent total phosphorus concentrations were well below 1 mg/L for the duration of the demonstration. As Total Phosphorus is not a currently regulated parameter at this particular plant, alum dosage was discontinued following the demonstration period. Ongoing Performance Since the completion of the optimisation, the average effluent ammonia-N concentration has remained low at less than 0.55 mg/L. On two separate occasions (August 2000; January 2001), problems with the aeration system caused insufficient dissolved oxygen concentrations in the final zone. As a result, complete nitrification was inhibited, and ammonia-N concentrations went as high as 9 mg/L. On average, effluent nitrate-N concentration has been 1.26 mg/L. Although the plant operators do not routinely analyse for TKN, results from the demonstration of plant performance conducted in March 2000 show effluent TKN concentrations to be < 1 mg/L. This equates to an estimated average total nitrogen concentration of < 2.81 mg/L. Graphs of actual effluent quality for the period from of August 1999 to February 2001 are located below.
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Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
10 9 8
6 5 4 3 2 1 0 28-Aug-99
17-Oct-99
6-Dec-99
25-Jan-00
15-Mar-00
4-May-00
23-Jun-00
Eff NH3-N
12-Aug-00
1-Oct-00
20-Nov-00
9-Jan-01
28-Feb-01
Eff NO3-N
Key Colony Beach WWTP Effluent Nitrogen Profiles
7
6
5 Effluent Phosphorus (mg/L)
Effluent Nitrogen (mg/L)
7
4
3
2
1 Phosphorus removal demonstration
0 28-Aug-99
17-Oct-99
6-Dec-99
25-Jan-00
15-Mar-00
4-May-00
23-Jun-00
12-Aug-00
1-Oct-00
Eff Total Phosphorus
Key Colony Beach WWTP Effluent Phosphorus Profile
301
20-Nov-00
9-Jan-01
28-Feb-01
Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
10
Effluent TSS (mg/L)
7.5
5
2.5
0 28-Aug-99
17-Oct-99
6-Dec-99
25-Jan-00
15-Mar-00
4-May-00
23-Jun-00
12-Aug-00
1-Oct-00
20-Nov-00
9-Jan-01
28-Feb-01
Key Colony Beach WWTP Effluent TSS Profile
10
Effluent BOD Concentration (mg/L)
7.5
5
2.5
0 28-Aug-99
17-Oct-99
6-Dec-99
25-Jan-00
15-Mar-00
4-May-00
23-Jun-00
12-Aug-00
1-Oct-00
Key Colony Beach WWTP Effluent BOD Profile
302
20-Nov-00
9-Jan-01
28-Feb-01
Application of a Membrane Bioreactor for Municipal Wastewater Re-use in the Florida Keys
Reverse Osmosis Pre-treatment The RO unit has been operated for only intermittent periods because the water distribution system has not yet been constructed. There has been no evidence of RO membrane fouling indicating that the ZenoGem® effluent was entirely suitable for direct feed to the RO. For the period of time when the RO unit has been operated, the reduction in conductivity has averaged greater than 98%. The TDS of the RO permeate has been measured at less than 100 mg/L, resulting in a high quality water entirely suitable for irrigation purposes. Development of Membrane Technology Since the commissioning of the Key Colony plant there have been a number of improvements to the membrane cassette configuration, and some have been implemented at Key Colony. For example, with the addition of automatic valves, the membrane air can now be cycled between the two trains, resulting in a 50% reduction in aeration requirements. As the membrane aeration makes up a substantial part of the total operating costs of the ZeeWeed®/ZenoGem® system, this reduction in net aeration requirements will equate to significant operating cost savings over the life of the plant. Other improvements to the design include more efficient spacing of the individual membrane elements in the cassettes, resulting in the ability to increase membrane surface area per cassette by over 20%, while at the same time improving the efficiency of the membrane aeration system, resulting in a reduced membrane cleaning frequency. This new cassette configuration has been in operation at Key Colony since August 2000, and the performance of the new membrane cassettes has equalled or exceeded performance of the original cassette configuration. Conclusion The Key Colony WWTP produces extremely high quality effluent, ideally suited for landscape irrigation. The plant not only meets all current permits, but also is well positioned to meet more stringent 5/5/3/1 regulations in the future. With ongoing research in membrane technology, the plant will be able to meet these regulatory requirements more efficiently, and with lower overall operating costs. Author: James W. Hotchkies, P.Eng. General Manager – Land Development Systems, ZENON Environmental Inc., 3239 Dundas Street West, Oakville, Ontario L6M 4B2 Tel: (905) 465-3030 Fax: (905) 465-3050 e-mail:
[email protected]
303
Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process by John Rudolph Ph.D., P.E. Clemson University, Clemson, SC, USA Frank Pepe P.E. Bioservices International, Hobe Sound, FL, USA Steve Eckstein Lakeside Corporation, Bartlett, IL, USA Abstract The Closed Loop Reactor (CLR) is a modification of the conventional oxidation ditch, which is a completely mixed, activated sludge process. The primary difference between the CLR and the conventional oxidation ditch is that the CLR has a deeper sidewater depth, which allows for the treatment of larger wastewater flows while minimizing land requirements. The CLR has a number of advantages over other types of activated sludge processes and is particularly suited to the Caribbean where ease of operation and maintenance and reduced power consumption are essential. Many of the advantages stem from the use of brush rotors in the CLR, rather than diffusers or surface aerators, for mixing and aeration. The rotors have a very high oxygen transfer efficiency, which can result in substantial cost savings, particularly in places where energy costs are high. Rotors require less maintenance than surface aerators and blower/diffusers systems and are not prone to the clogging problems and deterioration associated with diffusers. Furthermore, because the rate of oxygen transfer increases as the submerged depth of the rotor increases, the CLR is capable of handling influent flow variations with less operator attention than other activated sludge processes. Because of this, flow equalization of peak flows is generally not necessary. The CLR is also particularly suited for the treatment of small wastewater flows. Primary settling is not required ahead of the CLR, which simplifies the process flow as well as reduces capital costs. Another advantage of the CLR for small wastewater flows is that sludge handling is greatly simplified. Because the CLR can be designed to operate at long solids retention times (SRT’s) similar to the extended aeration process, the sludge produced is already digested and suitable for direct application to drying beds, thus bypassing the need for a solids stabilization train. For larger systems, the CLR can be designed to operated at a shorter SRT, similar to conventional activated sludge, which requires less oxygen, less biological reactor tank volume, and allows for biogas recovery. Finally, it is possible to achieve both nitrogen and phosphorous removal in the CLR by incorporating anoxic and/or anaerobic zones in the design of the reactor basin. Separate anoxic/anaerobic tanks with all of the associated solids return piping and equipment are not required as with other processes, which leads to reduced capital costs and simplified operation. Keywords: oxidation ditch, activated sludge, closed loop reactor, extended aeration, biological nutrient removal
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
Introduction The purpose of this paper is to share with the Caribbean wastewater community information about a wastewater treatment technology that may be particularly well suited for Caribbean applications. The information presented resulted from a study conducted by the authors to evaluate the efficacy of various wastewater treatment processes for the treatment of municipal wastewater in the Caribbean. The design flowrates for the five different facilities considered ranged from 1.5 to 20 million gallons per day (MGD). A variety of treatment processes were compared in the study to determine which process would be the most appropriate given the conditions typically encountered in the Caribbean. The factors weighted most heavily in the evaluation included capital costs, operation and maintenance requirements and reliability, solids handling, and effluent requirements. It should be pointed out at this point that only proven wastewater technologies were given serious consideration in the study. For example, a treatment technology that theoretically holds great promise in the Caribbean is anaerobic wastewater treatment. While this is a proven technology for the treatment of high strength wastewaters, its application to the treatment of domestic wastewater, which is much lower strength, has been limited and with mixed results (Schellinkhout and Collazos, 1992). Fixed media processes, such as trickling filters, were also considered. Although trickling filters are energy efficient, forced air is required in the warm climate of the Caribbean in order to maintain aerobic conditions. Besides potential problems with filter flies (Grady et al., 1999), the rotary distributor nozzles are subject to plugging, which results in non-uniform loading rates and a reduction in effluent quality. For these reasons, trickling filters were not given further consideration. Lagoons were also considered but, due to limited land area available, were not feasible. Because the client directed the author’s to design functioning, reliable treatment plants, novel and innovative treatment technologies without a proven track record were not given serious consideration. Of a number of processes considered, three were chosen for further study. Those processes included the sequencing batch reactor (SBR), the Closed Loop Reactor (CLR), and the Modified Ludzack-Ettinger (MLE) process. The results of the study indicated both to the authors and to the client that the most appropriate treatment technology was the Closed Loop Reactor (CLR). The MLE process for nitrification/denitrification was eliminated for several reasons including; significant operator skill requirements for control of flow to and from the separate anoxic tanks, problems experienced by the client in maintaining noisy blowers, diffuser plugging and deterioration and extensive, costly surface aerator maintenance. The SBR alternative was eliminated because it is a batch process requiring significant operator attention and the client felt that the use and repair of Programmable Logic Controllers (PLC’s) was too technical for the available operator staffing. The Closed Loop Reactor (CLR) is a modification of the oxidation ditch, which is a completely mixed, activated sludge process. It can be designed to operate at either short SRT’s (like conventional activated sludge) or at long SRT’s (like extended aeration), and can incorporate anoxic and anaerobic zones for denitrification and phosphorous removal within a single reactor. The primary difference between the CLR and the conventional oxidation
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
ditch is that the CLR has a deeper sidewater depth, which allows for the treatment of larger wastewater flows while minimizing land requirements. In the CLR process, a deflector baffle is located downstream of the rotor and directs turbulence from the rotor downward, which allows mixing and aeration to occur at greater depths than in a conventional oxidation ditch. Facilities utilizing this adaptation have been in operation for over twenty years with some operating at depths of 16 feet, compared to about 7 feet for the conventional oxidation ditch (Lakeside Corporation). Additional characteristics which render the CLR process more effective than other suspended and attached growth processes for the treatment of domestic wastewater in the Caribbean are discussed below. Process Flow The optimal process flow scheme differed substantially depending on the influent flow rate. The choice of a process flow scheme must balance the higher capital costs and operator skill required by more complicated process flow schemes with the substantial energy savings that can be achieved by utilizing the more complicated flow schemes. The authors determined that, given the conditions in the study, plants having influent flow rates less than 5 MGD (19 m3/day) were better served with simplified process flow schemes whereas for plants with influent flow rates greater than 5 MGD, a more complicated process flow scheme was most appropriate. The process flow scheme for the smaller plants will be discussed first. As with other wastewater treatment processes, raw wastewater must be screened and degritted at the plant headworks to protect downstream mechanical equipment such as pumps. Flow equalization was incorporated at this point to dampen peak flows because excess tankage was available. However, it should be noted that, depending on the peaking factor applied, flow equalization might not be required for the CLR process, as will be discussed later. After flow equalization, wastewater would typically discharge into a primary clarifier. However, because of its excellent mixing characteristics, the CLR is capable of operating without primary clarification, which results in lower capital costs and less equipment to maintain than other available treatment systems. Effluent from the CLR then enters the final clarifier, and is disinfected prior to discharge to the environment. Like other activated sludge processes, some solids leaving the clarifiers must be pumped back to the CLR as return activated sludge, in order to maintain the appropriate SRT, while the rest of the solids must be wasted. Unlike most other activated sludge processes, however, the CLR can be operated at long SRT’s, on the order of 25 days without supplemental mixing. For the three smaller plants studied with average influent flows less than 5 MGD, it was determined that the CLR would operate at an SRT of 25 days. While there are certain disadvantages associated with operation at such long SRT’s, such as higher oxygen requirements, a long SRT was chosen for the smaller plants in order to simplify the solids process train, minimize capital costs and improve operational stability. Operation at a long SRT aerobically digests the solids and produces a stable sludge that, depending on local requirements, might be directly land applied (unless there are problems with heavy metals, etc.). Thus, the solids processing train consisted only of a holding tank, followed by sand drying beds for dewatering. Underflow from the sand drying beds and supernatant from the
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
sludge thickener would be returned to the oxidation ditch for treatment. Therefore, the higher oxygen costs associated with operation at the long SRT were more than offset by the elimination of the need for expensive sludge digestion facilities. Figure 1 shows the process flow diagram for one of the smaller plants (1.5 MGD). This particular facility is a refurbishment of an old, non-operational, package contact stabilization plant. It is of interest to note that the 50-foot diameter final clarifiers were to be installed within the existing 75-foot diameter concrete tanks, which allowed the annulus to be used for flow equalization. Figure 1 Typical Process Flow Diagram Utilizing the CLR For a 1.5 MGD Average Influent Flow Plant
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
The process flow scheme for the larger plants was more complicated than that for the smaller plants. With the larger plants, primary clarification was employed. Further, the CLR was designed to operate at an SRT of 8 days (which is typical of most activated sludge processes) to reduce oxygen requirements (which results in fewer rotors) as well to reduce the basin volume (since far fewer solids must be kept in suspension). Because these changes resulted in the production of fresh solids, anaerobic digesters with biogas recovery were added to the process train for solids stabilization. Primary sludge was fed directly to the anaerobic digesters while waste activated sludge was thickened with a gravity belt thickener prior to being fed to the digesters. Biogas recovery with electric generator sets was included in the largest plant (20 MGD plus 0.1 MGD of septage). However, due to land space constraints and marginal cost effectiveness, biogas recovery and electrical energy production was not included for the 5.4 MGD plant. The economic feasibility of energy recovery from biogas must be evaluated on a case by case basis. Based on current energy costs in this particular area, it was calculated that the total capital costs of the electric generator sets would be recovered in three years for the largest plant. The energy produced from the biogas recovery system would have provided 39 percent of the total power needs for the facility. Finally, belt presses were used for digested sludge dewatering rather than sand drying beds because there was not enough land available for sand drying beds at the larger plants. Figure 2 shows the process flow diagram for the largest plant. This particular facility is a refurbishment of an old, non-operational primary treatment plant.
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
Figure 2 Typical Process Flow Diagram Utilizing the CLR For a 20 MGD Average Influent Flow (with 0.1 MGD septage) Plant
As shown above, the ability of the CLR to be operated without a primary clarifier and at a long SRT greatly simplified the process flow scheme for the smaller facilities. Capital costs were minimized and operational simplicity and reliability were maximized. For the larger facilities, any number of other activated sludge processes could have been chosen. However, the CLR was deemed the most appropriate technology for this application as well for the reasons discussed below.
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
Biological Nutrient Removal Neither of the process flow schemes presented above makes mention of separate anoxic or anaerobic tanks, which may lead the reader to conclude that removal of nitrogen and phosphorous were not required in the study. Nothing could be further from the truth since all of the facilities had to meet nitrogen limits of 10 mg/L and phosphorous limits of 4 mg/L. The ability of the CLR process to provide biological nutrient removal (BNR) within a single reactor is another significant advantage of the CLR process compared to other activated sludge processes. By incorporating BNR into a single tank, capital costs are reduced, not only because fewer tanks are required but also because all of the associated piping and pumps for transferring solids from one tank to another are not necessary. Energy costs are also reduced by eliminating the interbasin solids transfer required by other BNR processes. Also, far less operator attention and skill are required since return solids flows between basins do not have to be monitored and there is less equipment to maintain. Even in places where BNR is not required, the authors suggest that nitrogen removal should be strongly considered when building new facilities or upgrading existing ones. In warm climates such as the Caribbean, nitrification should occur in all activated sludge systems and typically accounts for 55% of the oxygen demand in municipal treatment plants with primary clarification. With denitrification, nitrate acts as an electron acceptor, thus reducing the oxygen required. Because denitrification allows for the recovery of roughly 60% of the oxygen required by nitrification, the oxygen requirements in a denitrifying facility will be reduced by about a third compared to a facility that is not denitrifying. As will be discussed in a later section, this can result in substantial savings in energy costs. Chemical costs may also be reduced if alkalinity addition is required, since denitrification allows for the recovery of 50% of the alkalinity destroyed by nitrification. With the CLR, designing for denitrification may also reduce capital costs because fewer rotors will be required since less oxygen is needed. Thus, the incorporation of nitrogen removal into the wastewater treatment process will not only reduce the likelihood of eutrophication in the receiving water, but will reduce the aeration costs of the facility and may reduce the capital costs (for the CLR) as well. BNR requires that bacterial solids cycle between aerobic, anoxic and anaerobic zones. In most conventional activated sludge processes, separate tanks are required for each of the three zones. With the CLR, wastewater continuously circulates around the ditch due to the action of the rotors. The CLR can be designed to be completely aerobic by the placement of rotors at fairly frequent intervals. Through strategic placement and/or operation of rotors, portions of the CLR will become anoxic or anaerobic. As the bacterial solids flow around the CLR, they are constantly cycled between the aerobic, anaerobic and/or anoxic zones. The introduction of influent and removal of effluent at the appropriate locations allows the designer to ensure that the BNR process is optimized. Thus, the CLR allows BNR removal to occur in the most efficient and simple manner possible.
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
Effluent Capabilities The effluent limitations that can be met with the CLR are similar to those that can be achieved with other activated sludge reactors. As shown in Table 1, effluent from CLR’s should meet all but the most stringent effluent requirements (Lakeside Corporation). Further, in areas with particularly low limits on nitrogen and phosphorous, removal of total nitrogen to 5 mg/L and total phosphorus to 1 mg/L via biological means can be accomplished with minor process modifications and additional equipment/tankage. Table 1 Effluent Limits Attainable Using the CLR
EFFLUENT LIMITATION
VALUE
5-day Carbonaceous Biochemical Oxygen Demand (CBOD5), mg/L
10
Total Suspended Solids (TSS), mg/L
10
Ammonia Nitrogen (NH3-N), mg/L
1
Total Kjeldahl Nitrogen (TKN), mg/L
3
Total Nitrogen (Total N), mg/L
10
Total Phosphorous (Total P), mg/L
4
Energy Efficiency For aerobic activated sludge treatment facilities in the U.S., energy costs comprise roughly 40 percent of the operational budget. In many countries in the Caribbean, energy costs likely account for an even larger proportion of the operational budget since labor costs tend to be lower and energy costs tend to be higher. In certain Caribbean countries, energy costs can account for as much as 80% of the operating budget. Thus, energy efficiency is an important factor to consider when evaluating different activated sludge processes. In a typical municipal wastewater treatment facility, the vast majority of energy is used for pumping wastewater and mixing/aeration. As was discussed in the BNR section previously, the energy required for BNR is minimized in the CLR because interbasin pumping of solids is not necessary. However, the most important factor to consider when discussing energy efficiency is the energy required for mixing and aeration since 75%-85% of the energy used by a wastewater treatment facility goes to mixing and aeration. There are five common methods to aerate wastewater in a wastewater treatment facility. The five aeration methods as well as their associated oxygen transfer efficiencies (OTE) are shown in Table 2. The rotors used in the CLR have roughly the same OTE as fine bubble diffusers, and are significantly more efficient than coarse bubble diffusers. Further, for the smaller plants running at long SRT’s, the differences in energy efficiency were even more pronounced than indicated in Table 2. This is because with other aeration methods, excess air or extra mixers were required in order to keep the high mixed liquor concentrations (associated with long 311
Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
SRT’s) in suspension. Because of its circular flow characteristics, the CLR was able to maintain solids in suspension with less energy than other aeration methods. Thus, the high OTE coupled with excellent mixing characteristics resulted in substantial savings in energy costs, especially for the smaller plants designed to operate at long SRT’s. Table 2 Comparison of Typical Oxygen Transfer Efficiencies For Common Aeration Methods
AERATION METHOD
OXYGEN TRANSFER EFFICIENCY (lb O2/hp-hr)
Rotor in CLR
3.5
Fine Bubble Diffuser
3.5
Coarse Bubble Diffuser
1.8
Surface Aerator
3.2
Submersible Aerator
<3
Maintenance Requirements/Reliability The data in Table 2 show that there is little difference in OTE between rotors and fine bubble diffusers. However, when designing a wastewater treatment facility, the maintenance requirements and reliability of the process may be as important as the energy efficiency, perhaps even more so when the availability of replacement parts and skilled labor are considered. This section will show that the CLR is superior to other activated sludge processes with respect to maintenance requirements and reliability. The advantages of the CLR with respect to maintenance and reliability are most pronounced for small facilities and for facilities where BNR is required. It was noted previously that, for small facilities incorporating the CLR, a primary clarifier is not required nor is a separate process train for stabilizing solids. The CLR allows a much simplified process scheme for facilities required to perform BNR as well. With the CLR, it is possible for BNR to occur in a single tank as opposed to the multiple tanks required by other processes. Thus, fewer pumps, pipes, tanks, electrical controls, and valves are required for BNR in a CLR compared to other processes. In both cases, the simplified process schemes result in less equipment, which translates to reduced maintenance and improved reliability. However, the benefits of reduced maintenance and improved reliability are not limited to small facilities and those performing BNR. The rotor used in the CLR to provide mixing and aeration is, in addition to being extremely efficient, the simplest, and consequently, the most maintenance-free method to aerate and mix wastewater. The rotor consists of an axle with metal “blades” attached vertically to it. The rotor is turned at about 60 rpm by an electric
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
motor. The blades are not prone to clogging and the only maintenance required is to lubricate the rotor bearings and the electric motor. Compare this to fine or coarse bubble diffusers which are far more prone to clogging (especially fine bubble diffusers) and require the maintenance of an air compressor with its associated valves and submerged piping. Surface and submersible aerators are also prone to clogging and require more attention than the rotors used in the CLR. Limited operator accessibility to surface and submersible aerators is also a concern when maintenance is required. Because of their inherent simplicity, the rotors used in the CLR reactor are more reliable and more easily maintained than other methods of aeration in activated sludge processes. Flow Variations Besides having a high OTE and low maintenance requirements, rotors have the additional advantage of being able to handle flow variations quite well. In many cases, flow equalization will not be required for CLR facilities. During periods of high flow, the water level will increase in the CLR. Since rotors are typically mounted at a fixed elevation, the depth of rotor immersion will increase as the flow increases. Conversely, the depth of immersion decreases during periods of low flow. Since the rate of oxygen transfer is directly related to the depth of immersion of the rotor, more oxygen is delivered when flow rates are high and less oxygen is delivered when flow rates are low with no attention or adjustments being required by the operator. For example, the Magna Rotor (Lakeside Equipment) delivers 3.24 times as much oxygen at its maximum immersion depth of 15 inches compared to its minimum immersion depth of 5 inches. Effluent weirs of the CLR are sized so that the immersion of the rotor at the minimum and maximum flowrates will result in the appropriate quantity of oxygen transfer. However, it should be noted that the rate of oxygen transfer may also be varied by adjusting the rotation rate of the rotor, with higher rotation rates yielding higher rates of oxygen transfer. Although this requires more operator attention, it may be appropriate in certain situations. Capital Costs As discussed earlier, the optimal process flow scheme is flow rate dependent. A cost comparison was performed between the SBR, MLE and CLR processes for facilities with small design flowrates as well as large design flowrates. It must be noted that the costs presented here are specific to the study and that these costs were calculated based on retrofitting existing facilities rather construction of new facilities. However, the capital costs presented below should adequately serve for comparison purposes. For a facility with a design flow of 1.5 MGD, the estimated capital costs are presented in Table 3. As the names imply, common costs represent the costs associated with unit operations such as headworks, whereas specific costs result solely from the process methodology itself. Estimated capital costs for a 20 MGD facility are presented in Table 4. Tables 3 and 4 show that the total capital costs of the three different process alternatives are virtually identical (about 5% maximum difference).
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
Table 3 Estimated Capital Costs in US Dollars of Three Alternative Treatment Processes For a 1.5 MGD Design Flow with Nitrification/Denitrification Treatment Process CLR SBR MLE
Common Cost 2,200,000 2,200,000 2,200,000
Specific Costs 1,300,000 1,200,000 1,300,000
Total Cost 3,500,000 3,400,000 3,500,000
Table 4 Estimated Capital Costs in US Dollars of Three Alternative Treatment Processes For a 20 MGD Design Flow with Nitrification/Denitrification, Septage Handling Facility and Biogas Recovery Treatment Process CLR SBR MLE
Common Cost 18,800,000 18,800,000 18,800,000
Specific Costs 8,200,000 6,800,000 7,300,000
Total Cost 27,000,000 25,600,000 26,100,000
Conclusions Ø The CLR is a versatile wastewater treatment method capable of being operated at either long or short SRT’s. Ø The ability to operate at long SRT’s allows for simplified process flow diagrams for facilities with small flows. Ø The CLR is capable of BNR within a single tank, which greatly simplifies the construction, operation, and maintenance of facilities required to remove nutrients. Ø The effluent limits achievable using the CLR are comparable to other activated sludge processes. Ø The rotors used in the CLR process transfer oxygen at a rate higher than or equal to the transfer rates of other aeration methods. Ø Because of its simplicity, the CLR is more easily maintained and operated than other activated sludge processes. Ø Flow equalization of peak flows is generally not necessary with the CLR. Ø For the study performed by the authors, the capital costs of the CLR were within 5% of the capital costs of equivalent SBR and MLE systems.
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Wastewater Treatment Utilizing the Closed Loop Reactor a New Twist to an Old Process
References Grady, C.P.L., Jr., Daigger, G.T., and Lim, H.C. (1999) Biological Wastewater Treatment, Second Edition, Marcel Dekker, Inc., New York, NY, USA. Lakeside Equipment Corporation, Guide to the Closed Loop Reactor (CLR) Process, RAD99, Bartlett, IL, USA. Schellinkhout, A. and Collazos, C.J. (1992) Full Scale Application of the UASB Technology for Sewage Treatment, Water Science and Technology, Vol. 25, No.7, pp. 159-166. Authors: John Rudolph Ph.D., P.E. Clemson University, Clemson, SC, USA Frank Pepe P.E. Bioservices International, Hobe Sound, FL, USA Steve Eckstein Lakeside Corporation, Bartlett, IL, USA
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Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater by William A. Telliard, Director Analytical Methods Staff, Engineering and Analysis Division (4303) U.S. Environmental Protection Agency Abstract Under the Clean Water Act (CWA), the U.S. Environmental Protection Agency (EPA) is required to restore and maintain the chemical, physical, and biological integrity of the waters of the U.S. Section 301 of CWA requires EPA to develop and publish nationwide effluent limitations for discharges from point sources. These effluent standards contain limits on substances that can be discharged directly into public waterways (direct discharge) or indirectly into public sewer systems (indirect discharge). The limits are based on treating or removing the substances and are determined from the performance of wastewater treatment technologies or from process equipment modifications. These limits are applied uniformly to every facility within a given industrial category or subcategory, regardless of the condition of the receiving water to which the effluent is discharged. More stringent, site specific limits can be applied to facilities based upon receiving water quality considerations. To date, effluent limitations have been developed and published for more than 650 subcategories of U.S. industries. Island communities, such as those in the Cayman Islands, present unique challenges for development of wastewater treatment systems because of political, sociological, and technological considerations. However, much of what has been learned in the U.S. about staged approaches to installation of wastewater treatment systems may be applicable to these island communities. The first part of this presentation will give details of the effluent guideline development process, including industrial categorization and sub-categorization, varieties of treatment technologies, economic considerations, use of test methods and data gathering for estimation of treatment system performance, and statistical analyses to produce the effluent limitations. The second part of the presentation will provide suggestions for approaches that could be considered by island communities for installation and operation of wastewater treatment systems, with an emphasis on beneficial use of wastewater. Keywords: wastewater, treatment, beneficial use, effluent regulations
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Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
Development of Technology Based Regulations in the U.S. Wastewater regulations in the U.S. are supported by technology based controls and waterquality based controls. Technology based controls are established by the performance of wastewater treatment technologies; water-quality-based controls are established by known or anticipated adverse effects of pollution on the environment. Technology based controls are implemented through Nationwide effluent guidelines; water-quality based controls are implemented through State water-quality standards. In the Clean Water Act (CWA), the U.S. Congress established the National Pollutant Discharge Elimination System (NPDES). Under NPDES, each point source discharger to a water of the U.S. is required to obtain a discharge permit. CWA also required EPA to establish technology-based effluent limits that are incorporated into NPDES permits. These limits are established from best available wastewater treatment technologies that are economically achievable. CWA also extended the water quality standards program to intrastate waters and required NPDES permits to be consistent with applicable State water quality standards. Thus, CWA established complementary programs of technology based and water-quality based pollution controls. Because the greatest immediate benefit could be realized from technology based controls, and because these controls could be defined in a straightforward way, emphasis was placed on implementing these controls. For technology based controls, best practicable wastewater treatment technologies (BPT) were to be implemented, followed by the best available treatment economically achievable (BAT). The Clean Water Act also prescribed that the BPT and BAT controls were to be implemented based on a categorization and subcategorization of U.S. industry. Over the past 25 years EPA has developed effluent guidelines using technology based controls for more than 30 categories and 650 subcategories of industry, at a cost of some $70 billion in sewage treatment plant construction alone. Categorization of Industry Developing technology based controls is accomplished by first identifying and characterizing the various industrial point source categories. (A "point source" is any discernible confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged.) Categorical regulations and standards are based on the principle that the best practicable control technology for one industry is not necessarily the best for another. The categorization process involves specific factors unique to a particular type of industry (e.g., dairy products; textile mills; petroleum refining; pesticides chemicals; metal finishing), and these factors assist in distinguishing between the classes, types, and sizes of the various industries. Combined with issuing regulations on a National level, they remove any regional or economic advantage to establishing site-specific pollution control requirements. Since 1972, the categorization scheme has been subject to several modifications. Originally, it consisted of 27 industrial categories listed in the Clean Water Act. The most significant change occurred in 1976 when a Consent Decree mandated a list of 21 groupings of Standard Industrial Classification (SIC) Codes for which toxic pollutant-based regulations were to be 317
Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
established. Later, EPA determined that several of the groupings identified by SIC codes were so diversified and dissimilar that additional and separate coverage was needed. After subsequent modification, EPA's efforts were focused on 28 primary industries. The list of industrial categories now numbers more than 30. Sub-categorization Segmentation of an industrial category is further required in order to account for individual or similar peculiarities between facilities. Subsidiary segments, as appropriate, generally take into account pertinent industry characteristics such as manufacturing process variations, water use, wastewater characteristics, and other factors that distinguish a specific grouping of segments within the industry. The regulations issued by EPA are based on engineering and economic studies that determine the subcategories within each major industrial category and on the wastewater characteristics and treatment capabilities of each category or subcategory. This development process requires examining the manufacturing processes, products, raw material, and by-products, and includes such factors as plant location and size, age of equipment, and identity and amounts of pollutants discharged. It also includes an evaluation of the cost and performance of the control technology, the financial status of the industry, and the impacts of the regulations on other media such as air pollution and solid waste (sludge) disposal. Details of the factors considered in characterizing a specific category or distinguishing between subcategories are contained in the public record for each effluent guideline. They are also summarized in the preamble to the regulation and in the supporting technical development documents. These documents are published by EPA as summaries of the Agency's study of the affected industry, and explain the technical rationale for establishing regulations. For the most part, sub-categorization has been based upon products, processes, and water use, and their effects on the character of the wastewater, either by pollutant type or pollutant loading. Levels of Effluent Limitations and Standards The effluent limitations and standards that implement the technology based controls contain limits on substances that can be discharged directly into public waterways (direct discharge) or indirectly into public sewer systems (indirect discharge). The limits are based on treating or removing pollutants and are determined from the performance of technologies available and, in some cases, from process equipment modifications. These limits are applied uniformly to every facility within the industrial category or subcategory, regardless of the condition of the receiving water to which the effluent is discharged. More stringent, site specific limits can be applied to facilities based upon receiving water quality considerations (see the section on Water-quality Based Pollution Controls). Development of the specific effluent limits requires detailed evaluation of wastewater discharges and treated effluents; e.g., the sources and volumes of wastewater, the processes, and the sources and types of pollutants in the plant. These evaluations enable EPA to characterize various controls and treatment options, determine their costs (both capital and annualized), and identify pollutant removals. Although the regulations do not require any
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Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
particular treatment technology, they do require plants to achieve effluent limits which reflect the proper operation of the model technologies from which the performance data were obtained to generate these limits. Data Gathering and Data Analysis To characterize wastewater treatment systems in a given industrial category and subcategory, EPA collects data from existing well-designed, well-operated treatment systems in that subcategory and from pilot studies of new or different treatment technologies. The characterization usually consists of sampling the influent and effluent from the various components of the treatment system and the system as a whole. Based on these data, EPA selects the best available treatment technology economically achievable (BAT) and performs a statistical analysis of the data to establish effluent limits for pollutants. The data form the basis of the regulation. After public comment from stakeholders and, where necessary, further data gathering and analysis, EPA promulgates a final rule containing the effluent limits. All of the data and the data analysis is contained in the record for the rule. Water-quality based Pollution Controls The goal of the Clean Water Act is to restore and maintain the chemical, physical, and biological integrity of the waters of the U.S. For the most part, technology based controls are adequate to protect the quality of the water to which effluents are discharged. Water-quality based controls are used when technology based controls are inadequate or for other instances in which a water body is adversely impacted. For water-quality based controls, a key element is the watershed approach to water quality protection. A watershed can be a river with its estuaries or a lake or series of lakes and the rivers and streams that feed the lake or lakes. Nearly all watersheds in the U.S. empty into the Atlantic or Pacific Ocean or the Gulf of Mexico. However, to effect pollution control, watersheds can be segmented into individual streams and stream segments. Water Quality Standards Water quality standards serve as the foundation for the water-quality based approach to pollution control and are a fundamental component of watershed management. Water quality standards are State or Tribal laws or regulations that: Define the water quality goals of a water body, or segment thereof, by designating the use or uses to be made of the water; Set criteria necessary to protect the uses; and Protect water quality through anti-degradation requirements. Although the Clean Water Act gives EPA an important role in determining appropriate minimum levels of protection for a water body, and for providing national oversight, the Act also gives considerable flexibility and discretion to States and Tribes to design their own programs and establish levels of protection above the national minimums. States and Tribes adopt water quality standards to protect public health or welfare, enhance the quality of water and serve the purposes of the Act. "Serve the purposes of the Act" has been interpreted by EPA to mean that water quality standards should: 319
Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
Include provisions for restoring and maintaining the chemical, physical, and biological integrity of the nation's waters; Provide water quality sufficient for recreation and for the protection and propagation of fish, shellfish, and wildlife ("fishable/swimmable"); and Consider other uses such as agriculture, industry, and navigation. Designated Uses The objective of a State or Tribal water quality standards program is to ensure adequate water quality for designated uses. Designated uses are defined as those uses specified in water quality standards for each water body or segment, whether or not they are being attained. To ensure adequate water quality for designated uses, a water quality standards program must: Provide the best information possible on whether designated uses are being attained and determine how to attain and maintain these uses Select water quality criteria that can be customized to each watershed Establish consistent, clear, and flexible water quality standards Encourage innovative, cost-effective approaches for attainment of standards Avoid costly requirements with little or no environmental benefit It is in designating uses that States and Tribes establish the environmental goals for their water resources, and it is in designating uses that States and Tribes are allowed to evaluate the attainability of those goals. Because water-quality standards perform the dual function of establishing water-quality goals and ultimately serving as the regulatory basis for waterquality based treatment controls and strategies, a State or Tribe often weighs the environmental, social, and economic consequences of its decision in designating uses. Reaching a conclusion on the uses that appropriately reflect the potential for a water body, determining the attainability of those goals, and evaluating the consequences of a designation, however, can be a difficult and controversial task. Appropriate application of this process involves a balancing of environmental, scientific, technical, economic, and social considerations as well as public opinion, and is therefore one of the most challenging areas of EPA's regulations. Suggestions for Island Treatment Systems Island communities present unique challenges for treatment system development because of political, sociological, and technological considerations. However, much of the information amassed by the U.S. in developing technology based controls and water-quality based controls can be applied to development of island wastewater treatment systems. In addition, newer treatment systems approaches such as re-cycling and beneficial use of wastewater can be an integral part of the design of a totally new treatment system, whereas retrofit of existing systems to take advantage of these approaches may not be possible economically. Treatment systems can be separated into two categories: those for wastewaters from domestic uses only, and those for treating industrial wastewaters (e.g., energy or mining). Domestic wastewater would include cooking, cleaning, and toilet wastes from individual households, hotels, and similar uses but would exclude industrial wastes because of the additional treatment required for nearly all of these wastes. Domestic wastewater treatment would be
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Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
primary treatment consisting of filtration and sedimentation. Sedimentation would occur in at least two ponds or lagoons and would likely need to have some means of odor control. The multiple ponds/lagoons would be operated and cleaned alternately. The design of a filtration/sedimentation system should allow for expansion to a secondary biological system by reserving space for aerobic and/or anaerobic digesters and a series of larger ponds for biological activity to continue and cease. Design of treatment systems to handle wastewaters from industrial facilities would benefit significantly from EPA's experience. Once the product/process is known and characterized, the regulations at parts 405 to 500 of the U.S. Code of Federal Regulations (CFR) could be consulted for applicable effluent limitations, and the references in the CFR would allow tracing of the regulations to the Federal Register (FR) rules and notices supporting the CFR. In turn, the FR publications would allow tracing of the rule to development and technical support documents in the EPA Water Docket. Current versions of the CFR are on line and the FR has been on line since 1994 through the U.S. National Archives and Records Administration (www.gpo.access.gov/nara). Information in the Water Docket is available from the Docket and through information retrieval companies in the Washington D.C. area. Beneficial Use of Wastewater Beneficial use of wastewater is a use alternate to discharge that results in a benefit to humans or the environment and does not create a further health or environmental problem. Beneficial use is, generally, an end use for the wastewater whereas recycling of wastewater is a use within the process that generates the wastewater. Typical beneficial uses would be: Irrigation of crops of crops consumed by humans. This use requires treatment to assure that uptake of pathogens and contaminants does not exceed levels specified for food. Crops consumed by animals (fodder). This use requires less treatment than food crops consumed by humans because human consumption will be indirect. Irrigation of grazing lands to levels necessary to preclude harm to animals. When necessary, animals can be removed from treated lands sufficiently in advance of slaughter to preclude transfer of pollutants to humans. Irrigation of non-crop vegetation, such as wind breaks, wetlands, golf courses, highway medians, parks, and landscaped areas. For wetlands, the effect on wildlife would be studied to determine the level of treatment that can be tolerated without environmental degradation and harm to wildlife. For parks and golf courses, additional treatment may be required to prevent infection from inhalation of microbes. Recharging ground water through injection or surface impoundments. Cooling water, primarily in power plants. Wash-down water for chemical reactor cleaning and rinse water. Domestic use; e.g., car washing, toilet flushing, dust control, and lawn and ornamental plant irrigation. A beneficial use usually requires transport of the wastewater to the point of end use. Therefore, the beneficial uses should be considered in siting of the wastewater treatment plant. For example, if the beneficial use will be crop irrigation, it may be cost effective to site the plant closer to the cropland to be irrigated.
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Development of Nationwide Effluent Limitations in the U.S. and Suggestions for Island Treatment Systems, including Beneficial Use of Wastewater
Sources of Information on Wastewater Regulations and Treatment The EPA offices with primary responsibility for wastewater regulations and treatment technologies are the Office of Science and Technology (www.epa.gov/ost) and the Office of Wastewater Management (www.epa.gov/owm), respectively. References to EPA's wastewater regulations and documents can be found at www.epa.gov/ost/pctoc.html and www.epa.gov/ost/pctoc.html, respectively. Treatment technology fact sheets can be found at www.epa.gov/owm/mtbfact.htm and information on wastewater treatment systems can be found at www.epa.gov/owm/secttre.htm. Author: William A. Telliard, Director Analytical Methods Staff Engineering and Analysis Division (4303) U.S. Environmental Protection Agency 1200 Pennsylvania Avenue Washington, DC 20460 Tel: (202) 260-7134 E-mail:
[email protected]
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality, St. Elizabeth, Jamaica. by Michelle Watts Water Resources Authority, Jamaica, West Indies. Abstract Rum has been produced in Jamaica from as far back as 1749, and for these two hundred and fifty two (252) years, the disposal of the organic waste generated from the rum distillery process, has caused pollution of both ground and surface water. At the rum distillery located in the parish of St. Elizabeth, the organic waste was discharged in an unlined earth canal which led to a limestone sink at the base of the Nassau Mountains. The waste quickly disappeared underground through the sinkhole and for years it was out of sight and out of mind. On the southern side of the Nassau Mountains, the North Elim River rises and flows south to join the Black River. Over time, the North Elim river became dark grey in color, had a pungent odour. Dead fish could be seen periodically floating down the river, and regular cycles of aquatic plant overgrowth were also observed. In 1999 a proposal was presented by the company to the government regulatory agencies, to stop the discharge of dunder into the sinkhole and implement a dunder fertilization pilot project. Waste would be stored in holding ponds and taken by trucks to the fields where it would be used to fertilize sugar cane via a sprinkler system. The proposal was accepted. The primary concern was whether the waste when applied to the fields would become part of the rainfall runoff thereby contaminating the nearby rivers or whether it would be absorbed by the soil, evaporate and the potassium content taken up by the cane plants, leaving little to run off into the river during heavy rainfall. The Water Resources Authority in conjunction with the NRCA and the rum producing company formed a joint monitoring committee to evaluate the impact of the dunder fertilization project on water quality through bio-monitoring and water quality assessments. After one year and six months of monitoring the data indicates that there is marginal improvement in the quality of the North Elim River to the south since the removal of dunder from the sinkhole. Although the rivers in the north which flow through the canefields to which dunder is applied, seem to be unaffected by the project for some months of the year, during and after heavy rainfall events, these rivers become contaminated by runoff (containing dunder) from the canefields.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
1.0 Background In Jamaica, rum, the alcoholic beverage, has been produced since 1749. Mollasses, the thick syrup remaining after sugar cane juice is crystallized by boiling, forms the basis for Jamaican rum. The mollasses is allowed to ferment and is then distilled to produce a clear liquid which is aged and blended to rum. A brown liquid organic waste, called dunder, is generated from the rum distillery process. In the case of one rum distillery factory, the dunder is discharged in an unlined earth canal which meanders away less than one kilometer from the plant and disappears underground via a limestone sinkhole at the northern side of the Nassau Mountains. For approximately eight (8) months of every year a continuous stream of dunder is discharged to the sinkhole at an estimated rate of 3 cubic feet per second, 7,340.7 m3/day. At the southern side of the Nassau Mountains, approximately 6 km south east of the sinkhole, a dark grey to black colored spring gushes up out of the rocks as the North Elim River. The North Elim River rises and continues to flow south, where it joins the Black River via the Upper Morass. The southern section of the Black River network has experienced major fish and shrimp kills, eutrophication, which results in overgrowth of water plants and choking of sections of the river, foul odors and unpleasant discoloration of the water.
2.0 Introduction In 1999 the rum distillery submitted a proposal, referred to as a pilot project, to utilize the waste (dunder) as a fertilizer for the sugar cane plants. The high potassium content of dunder was the important nutrient which would be taken up by the cane plant. This would in turn lead to cost savings in artificial fertilization of the cane fields. Dunder would no longer be discharged into the sinkhole to contaminate water resources. The proposal was to construct two holding ponds sealed with synthetic liner for storage of the dunder. From there, trucks would fill with the dunder, drive out to the cane fields and at specific points be linked to large hoses with sprinklers at the other end. Under the pressure of a pump, the dunder would be applied to the cane fields. The system was built and commissioned in December 1999. See Figure 2.1 Hose Being Connected To Truck Filled With Dunder
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Figure 2.1 Hose Being Connected To Truck Filled With Dunder
The then, Natural Resources Conservation Authority (now National Environment and Planning Agency, NEPA) the government regulatory body responsible for environmental management, accepted the proposal and required that a joint water quality monitoring committee be established to evaluate the effectiveness of the dunder fertilization project. The Water Resources Authority, Jamaica’s premier hydrologic agency, is represented on this committee and continues to play a lead role in the design and implementation of the monitoring programme. This pilot project is proposed to run for a three year period, 2000 to 2002, during which time monitoring of water quality will continue. Water quality data has been collected from December 1999 through to May 2001 and it is this data which will be presented, evaluated and used as the basis of preliminary conclusions on the effectiveness of the dunder fertilization project. 2.1 Hydrogeology The area is drained by the upper reaches of the Black River, flowing over stiff reddish brown clay which extends some forty (40) feet below ground surface, where it meets a white limestone. (See Figure 2.2 Lithological Profile at Raheen, Nassau Valley) The limestone is karstic in nature, as it is characterized by an extensive network of solution channels, which facilitates the rapid flow of groundwater. The Nassau Mountain is also a limestone aquifer and supports a number of springs and rivers, including the North and South Elim Rivers which emanate at the southern base of the mountain. (See Figure 2.3 Hydrogeology of St. Elizabeth)
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Figure 2.2 Lithological Profile of Nassau Valley Lithological Profile
Tight Brown Clay 37ft
Gravelly Clay
Groundwater Table
13ft Limestone
Figure 2.3 Hydrogeology of St. Elizabeth
Hydrostratigraphy of St. Elizabeth
Hydro stratigraphy Alluvium Aq uiclu de Alluvium Aq uifer Basal Aqu ic lu de Lim esto ne Aq uifer River
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
2.2 Surface Water Quality Before the start up of the dunder fertilization project, dunder, cane-wash water and plant washdown water, was led into the sinkhole resulting in the contamination of the North Elim River and southern sections of the Black River. With the introduction of the fertilization project, it is expected that the waste going into the sink hole would consist of washwater, less the dunder effluent. As such the following assumptions were made and tested. Assumptions If the fertilization project is successful:A. The quality of water at the North Elim and Black River in the south, should improve significantly. B. The quality of One Eye and Black River on the north is expected to be similar to its quality prior to the project and similar to points along the river which are outside the area of influence ie. the control points. If the application of dunder to the soil is managed successfully, it is not expected that dunder would form part of the surface runoff after heavy rains, but that it would be absorbed by and held within the soil, thereby preventing contamination of the nearby surface streams in the north. C. With heavy rainfall on the canefields, contamination indicators of the Black and One Eye Rivers should not show correlating spikes or increases.
2.3 Biomonitoring ‘Benthic Macro Invertebrates are widely accepted as sensitive and responsive indicators of the prevailing water conditions.’1 It is expected that with improvements in water quality, the composition of macro invertebrate communities will alter to reflect these changes, and a few specific organisms will be identified as indicators of poor water quality conditions and others as indicators of good water quality conditions. The primary objective of this aspect of the study is to determine whether, over time, polluted streams improve in quality. The composition of macro invertebrate communities will modify to reflect the improved water conditions.
1
John K., WRA Assessment Of The Impact of the Appleton Dunder Re-Use Project on Surface water’ February 2001.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
3.0 Methodology 3.1 Surface water Quality Monitoring Programme 3.1.1 Monitoring Network A total of seven surface water points were selected. Five were located north of the Nassau Mountain and two on the south of the Nassau Mountain. The two sample points in the south were selected in order to determine whether the quality of surface water would improve, since dunder was no longer part of the waste stream being led into the sinkhole on the north. (NB. Because of a direct hydrologic link, the rivers on the south were polluted by dunder discharged to the sinkhole in the north Figure 3.1 Water Quality Monitoring Network
Parishes
St. Elizabeth
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
3.1.2
Sampling Frequency
In order to obtain background water quality data, it was important to collect water samples prior to the application of dunder to the cane fields. The logistics of establishing a monitoring committee allowed for the collection of only one set of samples prior to start up of the project. During the first year of monitoring, samples were collected once every three weeks for the first seven months, then once every two months for the next four months. During the second year samples were collected once every four weeks from January 2001 to May 24, 2001. 3.1.3 Parameters Tested The parameters tested were designated, the Minimum Set and Full Set. On every sampling exercise a certain set of parameters were always tested, these were referred to as the minimum set. While less frequently, a larger set of parameters were tested, these were referred to as the full set. Full Set of Parameters (* Minimum Set) Nitrate * Phosphate * Potassium * PH * BOD * Dissolved Oxygen Calcium Magnesium
Chloride Bicarbonate Manganese Conductivity Total Dissolved Solids* Chemical Oxygen Demand Sodium Ammonium
To determine the chemical character of the water throughout the study area, the data was presented graphically using Stiff Diagrams. This allows for comparative analysis of different water quality or the emphasis of differences. 3.2 Biomonitoring Programme 3.2.1 Monitoring Network Seven bio-monitoring sample sites were selected. Four located on the northern side of the Nassau Mountain and three on the south. In the north, three sites were located on the One Eye River and the other below the confluence of the Black River and One Eye River. In the south, two of the points represent springs at the head of the North Elim River and the other point is further downstream on the North Elim River. See Figure 3.2 Bi-Monitoring Network.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Figure 3.2
3.2.2 Sampling Frequency Biomonitoring was conducted during the first year of the monitoring programme and samples were taken on eight occasions; February 9, March 30, April 5, June 7, August 9, October 12, December 13, 2000 and January 17, 2001. 3.2.3 Sampling Method Benthic macroinvertebrates were collected at each site using a standard kicknet (45 x25cm with mesh size 500m m). The net was swept through the marginal vegetation and sediments of the rivers. One minute replicates were taken at each site. The samples were then partially sorted to remove the larger pieces of sediment and debris, placed in plastic jars, preserved in 90% ethyl alcohol and labeled. At the lab these were further sorted and using a stereo microscope (mag.x7-x45) the invertebrates were identified to the family level and counted. Communities were then described for each site as follows; -
Diversity; the number of families Density; total number of invertebrates collected Proportion of gill breathers; total number of gill breathers divided by the total number of invertebrates collected. (John 2001)
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Diversity Biodiversity is normally higher in larger rivers where there are more niches available. Environmental stability also promotes high diversity since wide fluctuations in abiotic conditions restricts the community of generalists, ie. organisms not specialized for any particular environment. In unpolluted water, a wide variety of invertebrates is able to survive and reproduce. Pollution is therefore indicated by a reduction in the number of groups of organisms expected. As groups intolerant of polluted waters are eliminated, the community of resistant groups become more abundant.2 Density Density is primarily dependent on the availability of food resources in the channel3. Rivers that have more organic food material are able to support higher densities of benthic macroinvertebrates, especially those tolerant of low oxygen conditions. Organic pollution is often detected by an increase in the density of invertebrates.4 Proportion of Gill Breathers Gill breathing invertebrates are sensitive to changes in the oxygen levels dissolved in the water, as well as suspended sediment which effectively smother the gills. In unpolluted water, oxygen levels are sufficient to support a wide variety of gill breathers and non gill breathers. However, as oxygen levels decrease, usually in response to organic pollution, the proportion of gill breathing organisms falls and conversely the proportion of non gill breathers rises. (John 2001) 3.3 Rainfall Data There were several rainfall stations located within and around the study area, however two stations were selected for analysis, since these were the only stations with a complete set of data up to June 2001. The stations selected were Appleton # 1 and Raheen #1. The rainfall data reviewed covers the period January 1999 through to June 2001, and a comparison is made of monthly rainfall of this period and the thirty year monthly mean.
2
John, Kimberly., WRA Assessment of the Impact of the Appleton Dunder Re-use Project on Surfacewater’, February 2001. 3 Benke, Hall, Hawkins, Lowe-McConnell, Stanford, Suberdropp(1988) 4 John, Kimberly. WRA Assessment of the Impact of the Appleton Dunder Re-use Project on Surfacewater. February 2001.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
4.0 Results 4.1 Surface Water Quality Figure 4.1 Stiff Diagram – December 22, 1999
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Figure 4.2 Stiff Diagrams – April 26, 2001
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Figure 4.1 shows water quality at three points, the two upper diagrams represent water in the north and the lower diagram represents water in the south. There was no rainfall in December 1999 and at this time no rum was being produced and hence no dunder wass being generated or discharged to the environment. The diagrams indicate that these waters are Calcium Bicarbonate type waters, due to the dominance of white limestone in the geology of this area, and there are strong similarities in water type between the north and the south. Figure 4.2 represents a period of heavy rainfall and a time when dunder generation. The point in the south, North Elim River, shows elevated potassium and significantly elevated levels of manganese. Based on the literature, dunder contains manganese levels of 7.7mg/L and the levels detected were over 300mg/L (which is not easily explained). Potassium in dunder is normally above 7000mg/L, however with heavy rainfall, dilution is expected. The sample point at One Eye River at the East End of the fields, shows distinct elevated levels of manganese, indicating that dunder being applied to the fields further east was impacting river water quality at this point.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
4.1.2 Indicator Parameters The primary indicator parameter selected was potassium, the results are plotted below for the northern and southern regions. FIGURE 4.3
SURFACEWATER IN THE NORTH Potassium
Dunder Sinkhole One Eye River bef. Black R.
Potassium [mg/l]
20
One Eye R. eastern section
15
Black R. Bluehole
10
Black R. bef. One Eye R. One Eye River furthest east
5
k low
05/24/01
04/26/01
01/11/01
02/05/01
09/21/00
07/12/00
06/21/00
05/10/00
05/30/00
04/18/00
03/29/00
03/07/00
01/25/00
02/15/00
0
K high
Date
FIGURE 4.4
SURFACE WATER IN THE SOUTH Potassium Potassium Surface Water South
35 30 25 North Elim River
20
k low
15
K high
10 5 0 Date
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
4.2 Rainfall Data Figure 4.5 Daily Rainfall at Appleton #1 (1999 – 2001) Daily Rainfall Appleton 1 (181777810) 160
120
80
40
0 J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
1999
M
J
J
A
S
O
N
2000
D
J
F
M
A
M
2001
Date
4.3 Bio monitoring Data A total of 47 benthic macro invertebrate families were identified throughout the monitoring network. Two of the points on North Elim River had significantly less diverse invertebrate communities, with significantly lower proportions of non-gill breathers when compared to other sites. Diversity was significantly higher at B4 than at any other site and the proportions of gill breathing invertebrates were highest at the Clear Spring on North Elim Source and One Eye River at the north eastern end. (John 2001) Table 4.3 A Water Quality Classification of Bio Sites Based on Proportion of Gill Breathers (Source: John K., Feb. 2001) Proportion Breathers
Very Good
0.80 – 1.0
B2, B4, B6
Fair to Good
0.40 – 0.79
B5, B7
< 0.39
B1, B3
Poor
Of
Gill Sites
Water Quality
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Table 4.3 B. Water Quality Classification of Bio Sites Based on Diversity (Source: John K., Feb. 2001) Water Quality
Diversity (# of families)
Sites
Very Good
>15
B2, B4, B6
Fair to Good
7 - 15
B5, B7
Poor
<7
B1, B3
Table 4.3 C Recovery of the North Elim River (Source: John K., Feb. 2001) 1998* Dunder Present #1 #2 #3
1999** Dunder Present #1 #2 #3
-
3
3.3
-
2
4.8
-
5.4
Proportion of Gill breathers -
0
0
-
0
0
-
0.06 0.04
Diversity
* John, K., La Hee, J. & Hyslop, E.(2000) ** John, K. Unpublished data
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2000 Dunder Diverted S1 B4 B3 7.25
The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
5.0
Discussion of Results
The original assumptions were that if the project was successful:·
The quality of water at the North Elim in the south, should improve significantly.
·
The quality of One Eye and Black River on the north is expected to be similar to its quality prior to the project and similar to points along the river which are outside the area of influence i.e. the control points.
If the application of dunder to the soil is managed successfully, it is not expected that dunder would form part of the surface runoff after heavy rains, but that it would be absorbed by and held within the soil, thereby preventing contamination of the nearby surface streams in the north. ·
With heavy rainfall on the canefields, contamination indicators at the Black and One Eye Rivers should not show correlating spikes or increases.
5.1 Surfacewater Quality 5.1.1 Chemical Characteristics Of Surface water in the North and South Before the Start of the Project Stiff Diagrams The water in the south, at North Elim River, shows slightly higher bicarbonate levels than sample points in the north, which could be due to the source of the North Elim River which is underground and the rock type in this area is limestone. Time Series plots For all parameters tested prior to the start of the project, the readings fall within the ambient water quality standard range. It can therefore be said that the quality of rivers in the north, was good, prior to the project and in the period when no dunder was produced. 5.1.2
Surfacewater Quality in the North
In mid to early January 2000, rum production commenced and dunder was generated and discharged to the newly constructed holding ponds. Application of the dunder to the canefields also commenced in January 2000. The Time Series plots show two distinct periods of elevated readings of the primary indicator parameters for nearly all the points along the northern rivers. The months of (May and June 2000) and (March, April and May 2001). The following parameters showed very clear elevated readings; potassium, phosphate and BOD.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
The months of heavy rainfall correlate well with the months which show elevated readings in a number of parameters. 5.1.3 Surfacewater Quality in the South The Time Series plot for the North Elim River in the south, shows a slight elevation in April and May of 2000 and a significant peak in May 2001. Both potassium and phosphate show this pattern. See Figure 4.3 and Figure 4.4. If potassium is selected as the parameter most indicative of the presence of dunder, then the North Elim River also showed some response to rainfall events, even though dunder was not being discharged into the sinkhole. This response on the south to rainfall in the north is explained by the fact that sections of the canefields being fertilized with dunder are located close to the older dunder channel and in fact several of the canefields drain naturally into this channel. Therefore when dunder is applied to these fields during rainfall, the runoff washes some of the dunder directly into the channel and eventually into the sinkhole. 5.2 Biomonitoring 5.2.1 Surfacewater in the north The bio monitoring data indicates that water quality at two of the four sample sites in the north, could be considered very good; B4 and B6. These points were located further upstream along the One Eye River. The other two points, B5 and B7 located further downstream on the One Eye River and Black River were classified as fair to good. The points located further upstream particularly B6 was selected as the control point as it was located on the outer perimeter of the areas to be fertilized with dunder. The points further downstream were located within the fields to be fertilized and the results indicate that these points were affected more by the runoff from the canefields than those further upstream. 5.2.2 Surface water in the South Of the three points in the south, two were classified as poor, B1 and B3, both located on the North Elim River. These rivers were grey in color and had a foul odor. The site B2, referred to as the Clear Stream, rises as a small spring near the major source of North Elim River. The major flow at the source is dark and foul smelling, while the small spring nearby is clear and odorless. The data indicates that the Clear Stream is of high quality, with a large diversity of benthic macro invertebrates and a high proportion of gill breathers. Although both sources, clean and polluted, are from the same groundwater system, this difference in quality indicates movement of groundwater via discrete conduits or channelized flow, reducing the effect of mixing of water underground
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
6.0 Conclusion 6.1 Impact on Surfacewater in the north : based on water chemistry and biomonitoring The quality of rivers on the north changed during and immediately after heavy rainfall. Parameters such as potassium, phosphate and biochemical oxygen demand (BOD) increased significantly during the rainfall events of April/May 2000 and April/May 2001, indicating that the effluent (dunder) was being washed into the rivers with surface runoff. During the dry months the rivers appear to be unaffected by the dunder. The bio-monitoring data indicates that the sample points located further away from the areas where dunder is applied, are of higher quality, evidenced by more healthy aquatic ecosystems, while those points further downstream, such as B5 and B7, show signs of stress. Prior to this project, the rivers on the north (upstream of the factory) showed no signs of pollution. 6.2 Impact on Surfacewater in the south : based on water chemistry and biomonitoring There is marginal improvement in the quality of the North Elim Spring, however the water is still under severe stress, with very low diversity and consistently low proportions of gill breathers. Organic effluent (not dunder) from the factory is still flowing into the sinkhole and this evidently, retards the improvement at the North Elim Spring. The question of whether the present method of disposing of dunder on canefields, creates less of an environmental problem than before, is still being evaluated. It is evident that that during the dry periods, approximately eight months of the year, the dunder applied to the canefields remains in the fields and does not affect surface water quality. There is general agreement that the traditional method of discharge to the sinkhole, is unacceptable. It is also evident that the with the new system of field application, two areas are affected differently, surface water on the south is showing slow and incremental signs of improvement and a pollution problem is created in the north during rainfall periods. In this preliminary analysis it can be concluded that both the dunder fertilization project and the discharge of dunder to the sinkhole, are environmentally unacceptable, even though one may be considered a greater pollution problem than the other. A more effective alternative, which could be an improvement on the existing project, may have to be explored. 7.0 References Hem, John D. (1992) Study and Interpretation of the chemical Characteristics of Natural Water. 3rd Edition. John, Kimberly. (2001) A Study of the Impact of the Appleton Dunder Re-use Project on the Physico-Chemistry and Biology of Surface Water.
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
APPENDIX A
The Physiochemical Nature of Dunder Parameter
Literature2
Literature1
SRC (Mr. Bailey)
BOD5 [mg/l] COD [mg/l] TSS[mg/l] Ash content[mg/l] VSS [mg/l] Dry residue [mg/l] SS [mg/l] Nitrate[mg/l] Ntot[mg/l] P2O5 [mg/l] Chloride [mg/l] Magnesium[mg/l] Calcium[mg/l] Potassium [mg/l] Ptot[mg/l] Sulphate[mg/l] PH Copper[mg/l] Iron [mg/l] Manganese [mg/l] Zinc [mg/l] Cadmium [mg/l] Chromium [mg/l] Lead [mg/l]
33,500 94,400 --------1495 --1663 152.43 4633 1154 1182 7703 --3962 4 0.6 80.7 7.7 1.7 0.03 1.01 0.44
14,500 – 25,000 25,000 – 29,000 --0 – 0.13 --0 – 1.5 ----240 – 450 ----------44 – 92 --2.5 – 2.9 0.11 – 8.1 -------------
38,000 80,000 100,000 42000 4800 --1500 500 800 ----------270 1400 4 ---------------
1
Handbook of Industrial Wastewater Treatment (Mssr. Rueffer/Rosenwinkel) German Edition 2 Nutrient Recycling of Alcoholic Slops by Irrigation in Sugarcane Fields = Taiwan Research Institute
341
Parishes
The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
APPENDIX B
The Study Area #
Black River
#
#
Rum Distillery
#
#
ê
St. Elizabeth
One Eye River
#
Sinkhole Nassau Mountain
#
North Elim Spring
Black River
North Elim River
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
APPENDIX C
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The Impact of Dunder Fertilization of Canefields on Surfacewater Quality St. Elizabeth, Jamaica.
Acknowledgements This study was a joint effort between the government regulatory agencies; Water Resources Authority and the Natural Resources Conservation Authority (now National Environment and Planning Agency) and the rum producing company, Appleton Estate. Special mention must be made of the members of the Water Quality and Environment Unit of the Water Resources Authority; Mrs. Natalie Ferguson and Mr. Andreas Haiduk, who were instrumental in the production of relevant graphs, maps and charts for this paper. The management of the Water Resource Authority must also be recognized for the financial support given in the execution of the monitoring programme. Author: Michelle Watts Water Resources Authority Hope Gardens, P.O. Box 91 Kingston 7 Jamaica E-mail:
[email protected]
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study by E. Craig Jowett and Joe M. Rogers Waterloo Biofilter Systems Inc. Abstract The sewage treatment systems at CLUBLINK’S newest resort golf courses in Ontario are designed to handle large fluctuating flows of high-strength wastewater typical of major resort facilities hosting large social functions and tournaments. RattleSnake Point with 45 holes is designed for normal peaks of 60m3/d and 5-day tournament peaks of 120m3/d; Blue Springs and Kings Riding (both 18 holes) at 30m3/d normal and 40m3/d tournament peaks; and Rocky Crest (18 holes), which has lakefront resort residences attached, is designed for 140m3/d normal peak. The main purpose of the plants is to treat the sewage to a very high degree and create a useful resource for golf course irrigation. The treatment systems include: (1) 2-day capacity septic tanks with fine-screen effluent filters, (2) 0.3–0.5-day capacity recirculation pump tanks to dose the BIOFILTERS, (3) WATERLOO BIOFILTERS in buried concrete tanks or 10m3 polyethylene tanks in buildings, (4) recirculation equal to design flow for cBOD and ammonium removal and for mitigation of hydraulic surges, (5) aluminum sulphate addition to the septic tanks for phosphorus removal, and (6) ultraviolet disinfection of BIOFILTER effluent. Other important aspects of the designs are (7) a custom electronic remote monitoring system, and (8) professional operations management secured by CLUBLINK with a permanent, ongoing contract. The effluent quality has far exceeded the target numbers and is consistently in compliance after a 2-month start-up period, despite frequent overloading by strong wastewater. The success of the resorts is such that the sewage is often much higher strength than expected. The average BOD loading throughout the past two years, including the quiet winters, was 75% more than the average design loading of 250 mg/L cBOD, and during the busy summer months, was typically 200% to 500% higher. In the summer of 2000, the average mass of organic matter loaded onto the BIOFILTERS, as kg cBOD/ m3 filter medium/day was 60% higher than the peak mass design loading. Water conservation measures would explain the higher strength but not the higher mass. Careful management by the kitchen and cleaning staff has decreased the organic and nutrient loading significantly in 2001. The main challenge with the plants has been meeting ammonium limits during the first-year start-up period which coincides with the busy season and strong wastewater. With cBOD at >1000 mg/L and TKN at 100 mg/L, one new system nitrified >90% of the ammonium in the first weeks, but was still not compliant. The same overloading did not affect another system because it was already 12 months old and could adapt to this stress. Ways of diverting food wastes from the sewer were investigated and the results in two of the systems are much lower influent nitrogen and phosphorus values, and therefore less stress on the system. One system with very soft lakewater did not nitrify until sodium hydroxide was added to the wastewater to increase alkalinity.
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
The removal of total nitrogen to 22 mg/L at RattleSnake Point (60% removal) and to 10 mg/L at Blue Springs (75%) in the first 7 months of operation is significant. The effluent recirculation coupled with high organic strength leads to substantial total nitrogen removal by nitrification and denitrification reactions. Keywords: sewage treatment, golf resorts, irrigation re-use, phosphorus, nitrogen, disinfection Introduction The premier CLUBLINK golf resorts in Ontario are supplied with advanced treatment systems designed to treat sewage wastewater to the highest degree. These resorts re-use the treated effluent in the golf course irrigation system, an option that is becoming more important to golf courses, even in temperate climates like Canada (Gill and Rainville 1994). Stringent effluent criteria were set to meet both the company’s and the government’s objectives. Soil treatment of sewage was not an option due to lack of space, the difficult soils in some cases, and regulatory requirements. WATERLOO BIOFILTER designs were chosen to meet the objectives because of the reasonable capital costs, and more importantly because of the ease of maintenance for the passive system. The BIOFILTER system is a patented absorbent trickle filter which retains the wastewater in open pores of the foam plastic medium by capillary force, where beneficial microbes living on the pore walls can renovate the organic contaminants (Jowett and McMaster 1994; Crites and Tchobanoglous 1998). Septic tank effluent is sprayed over the top of the filter medium and it trickles down slowly through the pieces of medium, and drains out the bottom like a shower stall, rather than a like a bathtub. The technology works like an intermittent sand filter but with at least ten times the loading rate, while still providing the same effluent quality. Figure 1 shows microbes coating the interior of the filter medium and growing into the large open pores (~0.5mm diameter). The similarity to sand can be visualized, except that the BIOFILTER medium has open spaces where sand has narrow throats between the sand grains. Because the filter medium is manufactured, it is consistent in its quality, and because it is light in weight, it can be transported over great distances. Hydraulic overloads due to faulty plumbing, for example, can be handled without the filter medium plugging and backing up. The first two systems started up in May 1999 and the second two in May 2000. This paper describes the designs, the difficulties encountered and solved, and the ancillary components added to maximize treatment consistency and minimize maintenance. Treatment System Design Whether for a single house or a large trailer park, the WATERLOO BIOFILTER design consists of fermentation in a septic tank over a 2-day period, BIOFILTER aeration for removal of cBOD, TSS, and most ammonium, and then disposal when cBOD and TSS limits are only required. The filter medium is contained in concrete tanks below ground, or more commonly polyethylene tanks above ground in a garage-type building or other structure (Figures 2 and
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
3). Typical designs can be seen in Jowett (2001) in this volume, and are simply increased in size proportionate to the flow rate. In these resort case studies, however, limits for ammonium, phosphorus, and E. coli must also be met, and additional components were added to the design to achieve these limits without undue maintenance costs. The design parameters of the wastewater are shown in Table 1, and are based on normal sewage values, although it was known that actual cBOD values would be much stronger. The non-compliance and target effluent values are given in Table 2. Table 1. ClubLink golf resort influent values (median values mg/L; to June 2001) cBOD
TSS
250 250 Design 263 471 RattleSnake Point 1999 208 379 2000 133 52-1620* 2001 147 423 Blue Springs 1999 175 535 2000 49 156 2001 1010 277 Kings Riding 2000 327 114 2001 202/459** 74/88 Rocky Crest 2000 326/ 141/ 2001 * range provided; **resort/clubhouse sewage separated
TKN
TP
40 58 58 21 47 38 35 74 37 39/93 30/ -
10 13.1 6.1 2.4 6.0 6.2 1.2 8.5 2.7 3.3/9.6 4.7/ -
The wastewater coming into the treatment plants was stronger than expected, and correlated well with commercial success. However, high-strength and high flows combined proved to be a problem for removing ammonium adequately, but only during the first year start-up period. A plant with high-strength, high flows after start-up would be within compliance even though well above the design loading. Consultation with the cleaning and kitchen staff was successful in diverting much of the organic loading (e.g., scraping plates into garbage), and the strength decreased, making treatment easier during very busy periods. Ammonium Design: The design concentration of 40 mg/L TKN proved fairly accurate, on average, but did increase significantly in the busy season, often >100 mg/L TKN, and >98% nitrification would be needed to meet the effluent criteria (Table 2). Expecting that organic matter loading might be twice the design of 250 mg/L cBOD, the process design included recirculation of the treated effluent back to the septic tank (typically ~50%) to reduce the mass of organic matter to a level where thorough nitrification could take place. Re-circulation was carried out by gravity wherever possible, or by pump when needed. Phosphorus Design: Addition of liquid alum to a septic tank is a simple means of phosphorus removal developed in Ontario, and is controlled automatically by linking the alum pump to a sewage pump going to the septic tank or to an effluent pump to disposal, something that approximates the flow through the system. The strength of the alum is correlated with the expected loading of phosphorus. Depending on the source of the sewage, the alum flocculant will form a scum or sludge, but the septic tank needs to be pumped out typically no more than once a year. 347
Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
E. coli Design: Tests of BIOFILTER effluent carried out for ultraviolet disinfection effectiveness showed that a strong TROJAN UV unit can remove E. coli well below the required limits. The UV units used are stainless steel troughs with weir outlets and submerged lamps, and have operated continuously for more than two years without replacement of the lamps, and with only periodic cleaning. Treatment System Results Table 2 shows the effluent values of the golf resorts year by year, along with the compliance requirements and the target values. Generally the systems improve with age, even when the wastewater increases in mass loading. High mass loading is critical in the start-up phase (typically 1 month), where nitrifiers have not established themselves properly, and nitrification can be impeded by the high organic loading. After a few months, however, the BIOFILTERS can be overloaded and the system will still be within compliance. Effluent Quality: The results shown in Table 2 show that the BIOFILTER effluent has consistent quality year after year, and well within the effluent target values set by regulation. The treatment system design is to minimize cBOD in the effluent so that the ammonium levels can be maintained; hence cBOD and TSS values are much lower than required. The design to remove ammonium also has the effect of removing TN (total nitrogen = TKN+NOx-N). The TN values during the first year at three of the sites indicate removal rates of 60% in the buried concrete system where air is freely vented (Rattlesnake) and 75% removal in the polyethylene containers where air supply is controlled (Blue Springs and Kings Riding). The total phosphorus (TP) in the effluent is controlled by aluminum sulphate dosed at the expected concentration of TP in the influent wastewater in order to obtain ~1 mg/L TP. Depending on the kitchen and laundry habits of resort staff, the influent wastewater can have as little as 1 mg/L and as much as 30 mg/L TP. Table 2. ClubLink golf resort effluent values (median values mg/L; to June 2001) Compliance Target RattleSnake Point 1999 2000 2001 Blue Springs 1999 2000 2001 Kings Riding 2000 2001 Rocky Crest 2000 2001
cBOD
TSS
NH4-N
TP
30 15 3.8 2.0 2.1 6.6 2.3 1.8 9.0 2.0 5.0 3.0
30 15 4.0 3.0 4.0 4.0 3.0 3.0 8.0 4.0 3.0 5.0
2.5 2.0 0.2 0.4 0.2 1.2 0.4 0.1 1.4 <0.1 1.7 0.2
2.0-2.5 1.5-2.0 1.1 0.9 0.5 1.1 0.7 0.6 0.9 1.0 0.5 0.2
E.coli cfu/100mL 100 100 1 <1 1 1 1 1 1 1 1 1
TN n/a n/a 22.8 19.9 11.5 4.8 18.7 -
Seasonal Flow Rate Fluctuations: The BIOFILTERS react very favourably to flow fluctuations between busy and slack seasons, which in these cases are summer and winter, respectively. Figure 4 shows the effluent cBOD values (left axis) compared to the actual 348
Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
daily flow rate measured (right axis). During the start-up period in summer 1999, the flow rates range between 20 and 40 m3/d, and fall off to <5 m3/d during the first winter. The cBOD values are consistently <5 mg/L in both seasons. During the summers of 2000 and 2001, the flows increased to 30-45 m3/d and 40-50 m3/d, respectively, whereas the effluent cBOD remains constant at <5 mg/L. Daily Flow Rate Fluctuations: Expecting large fluctuations in flow rates due to banquets and tournaments, the systems were designed to store the wastewater in surge tanks with capacity of 0.3 times the daily flow. The pumps dose the Biofilters on a frequency-duration timed basis from the surge tank. Not only can the flows vary by ten times from day to day, the flows typically come in a 6-hour period in the day during a major function, and storage is important to maintain effluent quality, especially ammonium levels. Ammonium and Organic Mass Overloading: High flows and high organic content together are not uncommon in resort-type sewage systems. Kitchen and bar staff scrape plates into the sink instead of the garbage and that increases the stress on the system immensely. Figures 5 and 6 depict the mass loading on the BIOFILTERS at Blue Springs and Kings Riding resorts (right axis) compared to the ammonium values in the effluent (left axis). The mass loading is the kilograms of cBOD loaded onto one cubic metre of filter medium each day. These two systems are designed at 30 m3/d normal peak flows and 40 m3/d tournament peak flows, or to handle a mass load of 0.18 kg per m3 of foam during a normal peak day. At Blue Springs (Fig. 5) the actual cBOD loading was less than the design during 1999 startup, and the ammonium anomaly (day 75) was due to the small surge tank used at first. During September the mass load increased to over the design, but the ammonium level was within compliance because of the maturity of the system, and the increase in surge capacity. The mass load during summer 2000 was extreme at Blue Springs (Fig. 5), averaging twice the peak design loading, but because of the maturity of the system, the ammonium levels in the effluent were well within compliance. At Kings Riding (Fig. 6) the ammonium anomaly during start-up (day 60) was due to extreme mass loading of the system while nitrifiers were not well established (both cBOD and TKN overloading), although poisoning of the system by pesticides or cleaning staff was also considered. Even though the system had nitrified quickly and efficiently (Fig. 7), the combined high flow and high organic loading caused non-compliant ammonium values in the effluent where nitrification dropped below 95% efficiency. This was remedied immediately by adding two more BIOFILTER tanks but the system may have remedied itself as it matured. In areas of very soft water, alkalinity concentrations is inadequate for nitrification to occur, and sodium bicarbonate added to the sewage successfully mediates this shortfall, although significantly adds to the maintenance requirements. Kitchen Habits and Organic Mass Overloading: CLUBLINK kitchen staff were instructed to divert as much food waste as possible away from the sewage systems, and the cleaning staff to minimize anti-septic agents. The results are very positive as shown in Figures 3 and 4
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
for the summer of 2001 where mass loadings to the sewage systems were reduced greatly even when the amount of business increased. Remote Monitoring: These surface discharge sites are all monitored remotely by a custom SITEWATCH system that records temperatures, pump on and off times, flow rates, pressure switches, alarms, etc. and summarizes the data each day. Serious alarms are paged to the professional operator and to Waterloo Biofilter Systems Inc. Problem trouble-shooting is easy with the remote monitoring and data recording, and very difficult without it. Difficulties can be anticipated by daily inspection of the monitoring data, an example being the unbalanced cycling of pressure switches indicating the sticking of the rotating valve. This system has been a great boon to the efficiency of the systems. Conclusions The designs for treating high-strength wastewater from golf course resorts with high fluctuations in flow rates is successful when adequate surge capacity is provided. Low ammonium levels required for surface discharge are attainable when re-circulation is designed into the system to remove organic matter. Ultraviolet disinfection successfully removes pathogens in the effluent where suspended solids and colour are low enough. Remote monitoring is very beneficial, and working with the kitchen and cleaning staff to improve the raw sewage quality significantly improves effluent quality during periods of overloading. Re-use of treated sewage for irrigation is a valid goal, even in temperate ‘wet’ climates, and helps maintain a favourable reputation in the eyes of the public and the regulators. Acknowledgements The authors wish to thank Scott Kirby, Wendy Burgess, and Jim Molenhuis of ClubLink for their help and permission to use materials and Jeremy Kraemer for helpful criticism. References Converse, J. C. (1999) Nitrogen as it relates to on-site wastewater treatment with emphasis on pretreatment removal and profiles beneath dispersal units. In: Proceedings, Northwest On-Site Wastewater Treatment, University of Washington, Seattle, R. W. Seabloom, (Ed.), pp. 171–184. Crites, R. and G. Tchobanoglous (1998) Small and Decentralized Wastewater Management Systems. McGraw-Hill, 1084 pp. Gill, G. and D. Rainville (1994) Effluent for irrigation: wave of the future? In:Wastewater Re-use for Golf Course Irrigation , Lewis Publishers, Boca Raton, pp. 44-52. Hutchinson, N. J. and E. C. Jowett (1997) Nutrient abatement in domestic septic systems: research initiatives of the Ontario Ministry of Environment. In: Septic Odour, Commercial
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Wastewater and Phosphorus Removal, E. C. Jowett, (Ed.), University of Waterloo, pp. 81– 102. Jowett, E. C. (1997) Sewage and leachate wastewater treatment using the absorbent Waterloo Biofilter, In: ASTM STP 1324, Site Characterization and Design of On-Site Septic Systems, American Society for Testing and Materials, M. S. Bedinger, A. I. Johnson, J. S. Fleming (Eds.), pp. 261–282. Jowett, E. C. (2001) Re-use of treated sewage for irrigation and toilet flushing, In: Proceedings, Caribbean Water and Wastewater Association, October 2001, Cayman Island. Jowett, E. C. and M. L. McMaster (1995) On-site wastewater treatment using unsaturated absorbent biofilters. Journal of Environmental Quality. Vol. 24, pp. 86–95. Jowett, E. C., et al. (2000) Consistency of treated wastewater needed for household, irrigation and near-potable re-use. In: Proceedings, National Onsite Wastewater Recycling Association, Michigan, pp. 205–216. Townshend, A. R., et al. (1997) Potable water treatment and reuse of domestic wastewater in the CMHC Toronto ‘Healthy House’, In: ASTM STP 1324, Site Characterization and Design of On-Site Septic Systems, American Society for Testing and Materials, M. S. Bedinger, A. I. Johnson, J. S. Fleming (Eds.), pp. 176–187. U.S. Environmental Protection Agency EPA/625/R92/004. Washington DC.
(1992)
Guidelines
Author: E. Craig Jowett, Ph.D., P.Eng. President, Waterloo Biofilter Systems Inc. 143 Dennis Street, P.O. Box 400, Rockwood ON N0B 2K0 Canada www.waterloo-biofilter.com
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for
Water
Re-use.
Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
Figure 1. Photomicrograph of filter medium after 12 months loading, showing bacteria colonizing inner surfaces and growing into large pores. Pores are ~0.5 mm diameter.
Figure 2. Air photograph of Blue Springs golf resort showing attractive garage-type building (circled) housing the sewage treatment plant.
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
Figure 3. WATERLOO BIOFILTERS housed in portable polyethylene tanks 2.4 m diameter by 2.4 m high with controlled air flow using corrosion-resistant fans, each suitable to treat 5000 L/d.
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
Figure 4. Fluctuating hydraulic flow rates at RattleSnake Point golf resort from season to season do not affect the quality of the BIOFILTER effluent.
Figure 5. During start-up at Blue Springs in summer 1999, low surge capacity caused an ammonium peak, but after start-up, even extreme mass over-loading of cBOD (e.g., summer 2000) did not affect the BIOFILTER effluent quality. Staff training caused low mass loads in 2001 even with increased business.
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Four Golf Resorts Re-using Treated Sewage for Irrigation: A Case Study
Figure 6. During summer 2000 start-up at Kings Riding, high mass over-loading of cBOD and TKN caused an ammonium peak, which was mediated by adding more BIOFILTERS, the maturing of the BIOFILTERS, and by staff training.
Figure 7. Nitrification at Kings Riding initiated quickly but high organic and nitrogen loads caused nitrification to dip below 95%, producing an ammonium peak.
355
FAST® Wastewater Treatment Systems with Nitrogen Reduction: An Affordable Solution to Decentralized Wastewater and Economic Development by Raymond L. Peat, Vice President, Marketing Bio-Microbics, Inc. Abstract Economic development, both residential and commercial, is often severely inhibited by the lack of wastewater infrastructure. Water quality concerns are becoming more intensive on a watershed basis. Nutrient removal is a growing concern for the protection of sensitive groundwater areas and along coastal zones. The affordability of centralized sewers is becoming prohibitive and raising questions about their efficacy as the prime solution. FAST® wastewater treatment systems (used in non-sewered areas) are ideally suited for providing advanced secondary treatment of single family dwellings, clustered subdivisions, restaurants and other commercial applications on a decentralized basis. FAST systems can even be used to retrofit a failed conventional septic system, giving homeowners and small communities the innovative solutions they seek. Certifications of FAST will be listed, and a study on performance evaluations from the NSF International on FAST is provided. A brief history of the FAST process and its corollary applications in the marine, municipal and industrial industries will be presented. Schematics of the process will be shown along with a discussion of the FAST modules. Proven concepts and applications of decentralized wastewater treatment will be presented using these dependable technologies. Nitrogen removal continues to be a growing concern for water quality officials. Various species of nitrogen exist and are present in a wastewater stream. Nitrate is only one species. Ammonia and organic nitrogen are also present in significant quantities. Effective nutrient removal must involve all species to achieve real total nitrogen reduction. A technical discussion of the chemistry involved in the nitrogen cycle as it relates to wastewater will be presented along with technical descriptions of the nitrification/denitrification processes involved in biological treatment and the FAST process specifically. Description of FAST A FAST® wastewater treatment system is a pre-engineered modular wastewater treatment system/device designed to treat wastewater from residential, commercial, high strength and small community applications. FAST can also be used to retrofit and upgrade an under performing system, which may be biologically or hydraulically overloaded. Use of this remarkable system allows for responsible new development and the renovation of failed conventional systems. 356
FAST® Wastewater Treatment Systems with Nitrogen Reduction: An Affordable Solution to Decentralized Wastewater and Economic Development
FAST is an acronym for Fixed Activated Sludge Treatment. FAST is a fixed film, aerated system utilizing a combination of attached and suspended growth, capable of nitrification/denitrification in a single tank. The combination of fixed film media and activated sludge offers stable and effective treatment with extraordinary reliability. A FAST system cultivates large volumes of “friendly” organisms in the inner aerated media chamber to digest the wastewater coming from the home and turn it into a clear, odorless, high-quality effluent. The attached growth system assures that more organisms remain inside the system instead of being flushed out, even during times of peak hydraulic flows. This provides consistent treatment. During times of low usage, the large volumes of thriving organisms prevent a dying-off of the system, making FAST equally suited for intermittent use applications. FAST systems are commercially available and widely accepted by regulatory agencies. FAST systems are able to achieve regulatory approval in some of the most stringent environments. These approvals come as a direct result of FAST’s high levels of treatment and reliability. Sufficient conditions are present which allows nitrification and denitrification to occur in the same tank - without any system modifications. Special patented technology allows FAST to consistently reduce nitrogen levels - including nitrates and all other nitrogen species - by over 70%. Fats, oils and grease are also easily handled with FAST’s robust aerobic process. A FAST system can be expected to reliably produce an effluent of: BOD5 £ 10 mg/L TSS £ 10 mg/L Total Nitrogen £ 10mg/L (including nitrate) Installation of the lightweight and durable FAST system is very simple. The system insert simply mounts into a septic tank and is connected to the remote blower. Proper tanks can be made in country at or near the job site. FAST was designed to be not only scientifically efficient, but also dependable and very installation-friendly. Once installed, the FAST system is virtually maintenance free. Tastefully located below ground level, the clean, odorless FAST wastewater treatment system blends beautifully into any landscaping design. The only moving part, the quiet running blower, is conveniently placed above ground in an unobtrusive blower housing and can be located anywhere - up to 100 feet away. The FAST system requires no other filters or pumps. Individual FAST modules are currently available with treatment capacities from 2 cubic meters per day to 36 cubic meters per day per module (or up to 150 persons.) Multiple units may be used, in parallel or in series, to meet larger flow and waste strength needs. Please consult Bio-Microbics for specifics regarding high strength waste applications.
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FAST® Wastewater Treatment Systems with Nitrogen Reduction: An Affordable Solution to Decentralized Wastewater and Economic Development
Bio-Microbics can provide schematic drawings with basic dimensions and tankage volumes as a guideline for selection of proper tankage. Local codes and requirements vary significantly with regards to specific tank requirements. Each locally provided treatment vessel or tank containing FAST treatment systems can house a single system or multiple systems, depending on the size and design, giving engineers and project managers maximum flexibility. Bio-Microbics can assist in making arrangements with a local manufacturer to obtain proper tankage. FAST wastewater treatment systems are light weight, pre-engineered and factory assembled units designed to fit easily into containers for international shipping. The first compartment of the two compartment septic tank will act as the primary settling and anaerobic zone. The aerobic treatment is retained within the FAST insert. It is important to note that the systems are rated assuming garbage disposals will be used in the home. If garbage disposals are not used, then the treatment capacity for both units could be increased significantly. Disinfection devices such as ultraviolet light, ozonation, or chlorination can offer very reliable treatment when site conditions and disposal options dictate their use. Annual maintenance involves a system check of the above ground components - blower and control panel - to assure continuous problem free operation. The replaceable filter element located at the remote blower should be checked for replacement. The septic tank should be inspected annually to determine if pumping of sludge is necessary. Certifications FAST has been tested and Certified by NSF International, the most widely recognized independent certification organization for public health safety in the world. Attached is the NSF International Executive Summary displaying test results of FAST wastewater treatment system’s performance evaluation and nitrogen reduction information. In addition to ANSI/NSF Standard 40, Class 1, FAST was the first sewage treatment system to obtain certification by Canadian Great Lakes (the most stringent marine standard in the world). FAST also carries certification from the U.S. Coast Guard and the International Maritime Organization (I.M.O.) and rules from the U.K. Department of Trade. In addition, FAST possesses electrical safety certification from the E.T.L. certification (equivalent to the U.L. certification), and the European Union Compliance certification (C.E.) Corporate Summary FAST® wastewater treatment systems for residential and commercial onsite wastewater applications are manufactured and marketed by Bio-Microbics, Inc. Bio-Microbics is affiliated with Smith & Loveless, Inc., a worldwide leader in the design and manufacture of wastewater treatment equipment since 1946.
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Known globally for superior engineering and manufacturing, the Smith & Loveless companies are one of the most recognized water and wastewater transfer and treatment groups in the world. With locations on every continent, this innovative group of companies is known for high standards, proven technology, engineering expertise and manufacturing quality. The History of FAST In the early 1970’s, the U.S. Coast Guard had a problem. Ships cruising in the coastal waters were dumping wastewater overboard, causing excessive pollution. The Coast Guard decided to call in Smith and Loveless, Inc., a leader in the wastewater treatment industry since 1946. Smith and Loveless collaborated with a major ship builder and the University of Kansas in Lawrence, Kansas to come up with a solution. There were three criteria for the product to be designed: 1) It had to be fairly small in size; 2) It had to have low maintenance requirements, since the ships’ mechanics who would be maintaining the system had to be available for the much more critically necessary ships’ engines at any given time; and 3) It had to effectively treat wastewater with varying hydraulic flows. After much research and testing, the marine form of FAST was born. It utilized a fixed film media combined with activated sludge treatment technology so that bacteria clinging to the media would digest wastewater, producing a remarkably clear effluent that was a major improvement over the raw wastewater that had previously been going overboard. In fact, the system worked so well that engineers saw possibilities for many additional uses for the technology. As a result, there is now an entire family of FAST products. Bio-Microbics, Inc. manufactures the following FAST products: Marine FAST® - Used on many well-known cruise ship lines and in other place, Marine FAST is certified by the U.S. Coast Guard, the Canadian Great Lakes (the strictest marine standard in the world) and the U.K. based International Maritime Organization (I.M.O.) Marine FAST has been and remains the virtually undisputed worldwide leader in marine wastewater treatment systems. Modular FAST® - Larger FAST systems are designed for use in municipal and industrial wastewater treatment. The modular configuration allows multiple modules to work together to produce just the right size system for the application. Another advantage of Modular FAST is that each segment is of a moderate size, allowing pieces to be placed through small openings such as ships’ doorways before assembly into the final system. Mobile FAST® - Sometimes called Container FAST, this system fits inside a standard shipping container for transport via truck, rail or ship to remote locations. A popular application for Mobile FAST is resorts, where the system can be moved from season to season depending on where there are the most people in summer or winter months. MicroFAST® - Introduced to the market only in the past few years, the MicroFAST systems were actually developed in the 1970’s, before onsite wastewater treatment became a major
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concern for environmental protection. Utilizing the same tried-and-true technology as the other FAST systems, MicroFAST treats wastewater in a fiberglass or concrete septic tank to provide highly treated effluent that won’t clog lateral fields or pollute groundwater supplies. Tested and certified by NSF International, FAST provides a BOD and TSS levels of 10 mg/L for six to eight people or 600 gallons per day. It can also reduce Total Nitrogen levels, including nitrates, to approximately 10 mg/L for up to ten people or approximately 1,000 gallons per day. MicroFAST is pre-engineered to be sized based on population equivalents and/or flow and currently available in module sizes of 500, 900, 1,500, 3,000, 4,500 and 9,000 US gallons. Attached is a schematic drawing of Micro FAST. MicroFAST systems provide an economical method of wastewater treatment, and are ideal for applications in the Caribbean. HighStrengthFAST® - HighStrengthFAST is utilized in commercial applications where wastewater contains high waste concentrations, large oxygen demand for waste, or any place where the strength of the waste introduces special challenges. HighStrengthFAST is currently available with hydraulic capacities of 1,000, 1,500, 3,000, 4,500 and 9,000 US gallons. Attached is a schematic drawing of High Strength FAST. RetroFAST® - RetroFAST modules treat wastewater produced by typical family activities, including bath, laundry, and kitchen usage, and ranges from one to five persons. RetroFAST is currently available with hydraulic capacities of 250 and 375 US gallons. NitriFAST® - NitriFAST is capable of denitrifying wastewater consisting of high total nitrogen levels and having a greater oxygen demand than normal domestic strength waste with regard to denitrification. NitriFAST is currently available with hydraulic capacities of 500, 900, 1,000, 1,500, 3,000, 4,500 and 9,000 US gallons. Product Features of FAST FAST® wastewater treatment systems offer the following features: · · · · · · · · · · · · · ·
Hidden, installs entirely underground Makes marginal sites buildable Robust process handles even the toughest applications Simple, dependable retrofitting of under performing systems Quiet, automatic operation Flexible development and landscape planning Virtually maintenance free – less mess Minimal disruption Garbage disposal and dish-washer compatible Pretreatment or complete treatment Low cost, long-lasting solution Saves money versus centralized system Affordable options Renovates soil and leach fields
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FAST Applications Single Family Dwellings · Environmentally safe treatment allows full use of property by homeowners, children and pets · Proven high performance levels could mean reductions in lot size, separation distances and other limiting factors · Possible innovative re-use of precious water resources for irrigation · Advanced wastewater treatment system ready for next generation requirements Clustered Subdivisions · FAST may make previously unbuildable land useful and profitable · Modular design of FAST system allows project planners maximum flexibility · Builders and developers are able to purchase and install only when and where needed, saving large capital expenditures of a costly centralized system High Strength Commercial · Restaurants and other difficult high strength waste applications are easily treated with FAST’s robust aerobic process · Clubhouses, schools, trailer parks, office buildings and other commercial properties are natural fits for a FAST wastewater treatment system · With FAST’s reliable process engineering design, operation is simple and virtually maintenance free Retrofit Failed Systems · Failing septic systems can easily be retrofitted and upgraded with the simple, affordable design of FAST · Small communities now have a practical, proven alternative to cost prohibitive centralized sewer systems · Modernizing the wastewater treatment system with FAST will increase current and future value of the property Assurance of Proper Operation FAST systems come equipped with a simple and very effective control panel. Any malfunction (including blower power failure and high water conditions) would trigger both a visual and audible alarm. Expanded panels are available with additional features for a variety of applications. A SCADA system can easily be connected for remote monitoring. Bio-Microbics, Inc. manufacturers a monitoring device called TRACK to be released Fall 2001. TRACK is an acronym for Talking Remote Alarm Calling Kit. It is an electronic device programmed to monitor the operations of an appliance and notify a remote location in event of an alarm. Service providers are then alerted to perform maintenance on a unit so homeowners won’t have to hassle with malfunctions. Although TRACK is ideal for
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monitoring FAST wastewater treatment systems, it can also be used with any electronic appliance. Technical Specifications All system specifications and schematics are available for download as AutoCAD files on our website www.biomicrobics.com, listed under technical specs. Power required: Electrical requirements vary according to model size. Please contact BioMicrobics or a dealer near you for more information on the FAST system that’s right for your application. Underground housing: FAST systems can be housed in concrete, fiberglass, steel or plastic tanks. Always check local regulations before installing or altering a wastewater system. Contact Bio-Microbics or a dealer near you for more information on the availability of proper tankage in your area. Dispersal Options: Check your local regulations. The extraordinarily high treatment levels may allow reductions in drain field areas, use of treated water for irrigation or other innovative discharge methods. Capacity: Available in several convenient, affordable sizes and configurations. Please contact Bio-Microbics or a dealer near you for more information on the FAST system that’s right for your application. Environmental Protection FAST systems greatly reduce groundwater contamination and help protect the delicate ecosystem. Potentially harmful nitrates and all other forms of nitrogen are removed at unparalleled rates (more than 70%) with the patented FAST process. FAST is made with 100% corrosion resistant and post-consumer recycled materials. Use of this remarkable system allows for responsible new development and the renovation of failed systems. Water treated from the FAST unit can be reused after automatic filtration for irrigation and landscaping purposes. It can be dispensed at night via a spray method where pipes connect to spray emitters that are dosed by an effluent pump. The water can also be reused through a drip method where drip tubing is placed underground and dosed by an effluent pump. Nitrogen Removal Nitrogen is present in many forms in the environment. Nitrogen is an essential constituent of all plants and animals. The air we breathe is 78 percent nitrogen by volume and 75 percent by weight. The movement and transformation of these nitrogen compounds through the biosphere is characterized by the nitrogen cycle. In wastewater treatment, organic nitrogen comes from urine, fecal matter, garbage disposal waste and ammonia based household cleaners. A majority of the organic nitrogen comes from urine in home wastewater.
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Organic nitrogen is converted to ammonia nitrogen (NH3) by a process referred to as ammonification. When ammonia nitrogen is hydrolyzed in water, it becomes into the ammonium ion (NH4+). Generally speaking, these two forms of nitrogen are referred to as ammonia nitrogen. Ammonia nitrogen is converted in the nitrogen cycle by nitrifying bacteria which provide the conversion from ammonia nitrogen to nitrite nitrogen (NO2). A second biological reaction occurs which transforms nitrite nitrogen to nitrate nitrogen (NO3). These two biological reactions are coupled and proceed rapidly to the nitrate form. Therefore, nitrite levels are usually quite low. The nitrate form of nitrogen may be used in synthesis to promote plant growth or it may be subsequently reduced by denitrification. Denitrification is the biological reduction of nitrate to nitrogen gas. The denitrification step occurs in an anoxic (without oxygen) reaction in order to remove nitrogen from the wastewater. There are several laboratory tests used to measure the different forms of nitrogen. In order to determine organic and ammonia nitrogen, the test commonly used is Total Kjedahl (pronounced “kel-doll”) Nitrogen (TKN). This test parameter is commonly used for the influent wastewater to determine the total amount of nitrogen present in the wastewater. Since TKN measures both ammonia nitrogen and organic nitrogen, it is sometimes necessary to also measure the ammonia nitrogen using a different test. This will determine what fraction of the TKN is associated with the organic nitrogen. The tests commonly run on an effluent are TKN and nitrate nitrogen. Another test that may be run is that for nitrite nitrogen. The nitrite nitrogen is not generally measured because it is generally assumed to be zero, and the typical measurement should run from 0.1 to 0.2 mg/L. The total nitrogen of an effluent sample is assumed to be the TKN plus the nitrate nitrogen measurement. This would measure the organic nitrogen, ammonia nitrogen and nitrate nitrogen. Attached is a data summary of nitrogen reduction tests from the FAST systems for residential and high strength applications. Under normal conditions an average of over 83% of total nitrogen can be removed with the FAST wastewater treatment systems. Conclusion Bio-Microbics is pleased to have presented this information to you. We are including several supporting attachments for inclusion with the publication of the proceedings. We would welcome the opportunity to answer any questions regarding FAST technology or to discuss the suitability of FAST for a specific application.
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Author: Raymond L. Peat, Vice President, Marketing Bio-Microbics, Inc. 8450 Cole Parkway Shawnee, KS 66227 Tel: (800) 753-(FAST) 3278 Tel: (913) 422-0707 Fax: (913) 422-0808 www.biomicrobics.com
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Hazardous Wastes Management in French Islands by Eric Coppet & Vinci Environment Abstract In this document we will try to explain the special case of the French islands regarding to the special industrial wastes. We will expose the difficulties met in the organisation and the management of this activity, the cost of the treatment of these wastes, and the result of such kind of problems on the environment. We will then present different projects that are being developed in Guadeloupe, French Guyana, and Martinique in order to face this situation. And finally we shall pull resources to treat locally all Caribbean special industrial wastes.
Introduction Management of hazardous wastes is a growing concern in many countries. Improper management and disposal of hazardous waste is an increasing problem as these substances pose serious threats to public health and environment. The cost of proper management is very important and therefore illegal dumping is common in many areas. A strict control and regulation is the only solution to prevent future problems. Waste management is submitted to a very precise regulation, especially when it concerns hazardous wastes. Their incidences on the environment and the human health lead to the creation of specific and rigorous procedures. The Caribbean area is not an exception. French islands with their particular status, as they are overseas French departments, are under the French legislation. So, concerning the management of their wastes, they must refer not only to the French legal Frame, but also to the European regulation. They have to face various problems due to their location, to the lack of structures permitted to collect the hazardous wastes for proper treatment or disposal at a local level, and to the cost resulting to the transport to appropriate overseas centres. In order to meet with theses difficulties, some projects are in discussion for treatment at the place of production (We mean locally) of the hazardous wastes. The main aims of those projects are the elimination of these special wastes in the Caribbean area, the elaboration of measures reducing the production, and the protection of the environment. Indeed, we believe that the protection of this beautiful archipelago must be founded on an overview and a global analysis of waste’s collect and treatment in all the Caribbean area.
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The Special Case Of The French Islands 1.1 Regulation and application in French west Indies (FWI) As mentioned above, because of their particular status FWI are under the French and the European regulation. However, only a part of the process is realized in Martinique, as there are no centres permitted for the elimination process. So just the laws concerning the collection, internal transport and the dispatch to national centres of hazardous wastes elimination are really in force in the FWI.
v French Legal Frame In France, four most important laws exist that determine the environmental scheme for wastes management : -
Law of 15th July 1975 Law of 19th July 1976 Law of 13th July 1992 Law of 10 October 1996
These laws determine what a hazardous waste is, and explain the collect, the transportation, and the treatment of these wastes, and oblige, anyone that products or gets some wastes which present a harmful character for the environment and human being, to eliminate or get it done by someone else in accordance with the law, as the owner keeps the responsibility of his substance. (L. 75-633 of the 15th July 1975) Are considered as wastes, all products issued of a production, transformation or using process, and generally all products considered as harmful for the environment and which are abandoned or designated to be abandoned by their owner. Are considered as hazardous wastes, all substances that present a toxic, igneous, reactive, or corrosive characteristic (determined by analytical testing in a laboratory) and needs special elimination treatment. These wastes can be hazardous to human health and the environment if they are not handled and disposed of properly. Because of their particularity, and the dangers they represent, they are submitted to a strict elimination process. This elimination can be done directly on the production site if an elimination procedure and process exist, or in a specific private centre.
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v European Legal Frame The European regulation concerning the elimination of hazardous waste complete the French regulation and gives a European dimension to this activity, in order to harmonize the procedures and to improve the protection of the environment in the different member states. Two rules are really significant on hazardous wastes : -
Council Directive 91/689/EEC of 12 December 1991 Council Regulation 259/93 EEC
They envisage community measures to improve the conditions under which hazardous wastes are disposed of and managed to apply a precise and uniform definition of hazardous waste based on experience. They specify the measures of control necessary to identify the type and the quantity of wastes. In the case of hazardous waste, inspections will cover particularly the origin and destination of wastes. They also state that Hazardous waste will be properly packaged and labelled in accordance with the international and community standards in force. v Regional Plan for the elimination of hazardous wastes The main expense is the shipping to France due to the fact that there is a lack of structure for the management of the hazardous waste in the FWI, which results in an important cost for the elimination of these substances and because of this high cost generators do not use the legal way to eliminate they hazardous waste. Conscious of the dangers of this situation to environment and human health, the public authorities in FWI decided to react and to elaborate, in accordance with the order of the bylaw of 18 November 1996, a regional plan of elimination of hazardous wastes. This regional plan foresees for the next ten years, certain measures to reduce the production of hazardous wastes, to improve the procedures in force in the FWI and to create authorized structures for the treatment directly in FWI. Considering their location and their particular status, it would be interesting to elaborate a inter-regional plan for the elimination of wastes. This scheme for elimination of wastes in the Caribbean area takes into account an inventory of the existing infrastructures for an inter regional waste management system. 1.2 Treatment and elimination process A hazardous waste management system should include regulations governing the storage of hazardous waste at the generator’s site or at any other transfer or disposal facility. It is
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therefore not acceptable to allow generators to stock all kinds of hazardous wastes, and not over an extended period of time in order to avoid the problems of disposal. Industries that treat their waste on the site still need a place to dispose of the residues from their treatment systems. Also industries which cannot afford to treat their wastes on the site need access to treatment and disposal facilities. The fact that traditional landfill sites are unsuitable and no longer acceptable for hazardous waste disposal will complicate matters. Hazardous waste facilities frequently comprise storage, recovery and treatment stages as well as final disposal. Various ways of treatment exist for hazardous wastes. it depends of the nature of the waste to be considered : -
Technical Storage area : The final disposal for many hazardous wastes or their treated residues is controlled land disposal. But it is important to understand that with the new regulation dumping (landfill) as defined for general wastes does not exist anymore. However, a properly located, engineered and operated hazardous waste technical storage area is a major facility and is not to be confused with the uncontrolled or open dumping that frequently occurs. Operation of the landfill will include requirements for pre-treatment and packaging of wastes, control and recording of the burial of different waste types, planning and preparation for spills and accidents and regular monitoring of the surrounding environment. Such controlled or "secure" technical storage areas should be used only for the minimal quantities of remaining wastes after all possible reduction and treatment has been carried out.
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Incineration : Incineration involves the thermal destruction of gaseous, liquid or solid wastes. Thermal oxidation converts complex organics into simple compounds, greatly reduces waste volumes and can recover the heat content of wastes. Incineration requires relatively high temperatures (typically above 1000oC), normally requires control of flue gases and generates small quantities of ash or slag. The key operational characteristics are : the temperature, the residence time and turbulence in the combustion chamber, all of which affect the efficiency of the destruction. A poor installation can emit particulates, acidic gases, unburned wastes. Some wastes, require very careful control, to ensure that minimum temperatures are maintained. The incineration of selected wastes (used oil for example) is possible in high temperature process plants such as cement kilns. 377
Hazardous Wastes Management in French Islands
Incinerators in France are submitted to important rules mentioned in the order of bylaw of 10 October 1996 (careful gas cleaning and monitoring are required). -
Reusing Process : some hazardous wastes are reused such as used oils, that serve as fuel for some special materials.
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Recycling Process : imply a pre-treatment or complete treatment of waste and its transformation into something else. Most often they are used as a source of energy (electricity, water, …)
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Sterilization : Hazardous wastes can be converted to non-toxic or less toxic substances by chemical, physical, and biological means, such as neutralization, combustion, low-temperature thermal decomposition, and bacterial decay. Such measures, while effective, present some problems and are clearly not as desirable as preventive measures to include in all hazardous waste management. It’s only recommended for hospital wastes.
2. Special Wastes Existing In The Fwi
Hazardous wastes
Martinique
Guadeloupe
F. Guyana
Hospital wastes Animal organic wastes Refinery wastes, oils,… Solvents Used Batteries Used tyres
60 T/year 1800 T/year 3000 T/year 300 T/year 150 T/year 500 T/year
120 T/year 1200 T/year 2700 T/year 150 T/year 150 T/year 2000 T/year
400 T/year 200 T/year 4000 T/year 150 T/year 200 T/year 800 T/year
3. Projects Developed Around Wastes Management Organisation and management waste treatment do not really exist in FWI. Actors directly or indirectly interested in the elimination process (transporters in particular) are not well informed about procedures and sometimes they refused some kind of wastes. So how can we really treat some hazardous wastes under those conditions ? Some projects are discussed to improve the situation. We would appreciate to develop a interregional plan for FWI, and more generally for the Caribbean islands. v French Guyana : based on the French national experience of certain specialized businesses that use used oils as fuel for cement kilns, and to answer to the law that favours the local treatment, EGTS a subsidiary of SEEN company elaborated a project to use used oil in asphalt plant. This process requires some changes on the
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materials of the manufacturing industries interested, and some investments for the pre-treatment of these substances. The interest of such a project is to reduce the cost of treatment as the used oils are directly treat in Martinique and then injected into the kilns of the asphalt plant. They started using this process some months ago. We hope to get some good results from this project. v In 2002, Martinique will be provided with an authorized incinerator for home wastes and hospital wastes. This incinerator called “La martiniquaise de valorisation” will complete the regional plan of elimination of open dumps. The collect organized by Ecompany a subsidiary of the SEEN group, is not enough. We need to complete this first step with a global treatment waste management directly in Martinique. Another project has been submitted to the authorities which consist in the creation of a centre of elimination of hazardous wastes : SOTRADIS. 4. A New Project For Hazardous Wastes : SOTRADIS 6.000 tons of hazardous wastes a year are produced in Martinique and 1.600 tons of animal organic wastes. And in this island exist no infrastructures for the elimination at a local level of theses substances. The cost of elimination is increased by the transport towards Europe. The same situation exist in others island in the Caribbean area. The problem is growing. Some private industries (SEEN, Vinci Environment, E-company and SPEIC) decided to find and to propose together a solution to this problem and in order to organise the elimination process in Martinique : SOTRADIS. This society will have the responsibility of the construction and the exploitation of a hazardous waste treatment unit in accordance with the regulation in force, the assistance of the industries in their wastes management, the protection of the environment. In a first step this unit will essentially take in account wastes producing in Martinique.
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Following in-depth study of an independent consulting company, we have compiled this synopsis : Wastes
Weight
Type
T/an
Medical wastes Animal organic wastes
60 1800
slop
300
Used oils
3000
Used tyres
500
Other hazardous liquid waste
250
Other hazardous solid wastes
515 T/an
6425
The starting date for this unit is previous in 2003. 4-1 Technical description of the plant Conclusion : Maybe it will take part to the regional and interregional plan that will be developed in the next years for waste management in the Caribbean, and will represent the solution for all the islands that have to face the same situation. Author Eric Coppet ZI La Lezarde 97232 Lamentin Martinique E-mail:
[email protected]
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Establishing Partnerships for Effective Solid Waste Management by: Valerie Beach MPH., PE/PA Manager SWMU/CWSA, St.Vincent & the Grenadines Abstract Introduction: Given the changes in consumption patterns, and in the amount of generated waste in a time of great technological advancement, the public demand for action and for the improvement of conventional methods of managing Solid Waste is resounding. It then becomes the responsibility of the Service Providers to respond to these demands by utilizing every necessary means i.e. the latest technologies to achieve the appropriate positive outcomes on all sides. It is paramount that as Service Providers, we fully comprehend the basic concerns, issues and needs of the consumer in order to establish and nurture the partnerships forged between the consumer and ourselves. This approach will play a vital role in developing positive solutions to the problems that face us all. Objectives: 1. To increase the general fund of knowledge of the consumer, so that they will be properly educated, and able to make informed decisions. 2. To educate the general public and other stakeholders about Solid Waste Management programmes, so that they will be able to have input into, and contribute to the design and structure of such programming. 3. To involve consumers in the development of new projects within their communities so that they will be a part of the process and be able to take ownership. Methodology: In order to achieve these objectives we need to employ a variety of approaches. These may include Customer Quality Surveys, Community Outreach Programmes, and School Programmes. Community Consultations and Focus Group Discussions will aid in soliciting ideas and suggestions from consumers and other stakeholders in whose communities we will be working. Involving the business sector via employee in-service training programmes, sponsorships for special projects, and by encouraging privatization of recovery/recycling projects will further enhance our efforts. It is imperative that we also provide an efficient and reliable collection and disposal service and good information management systems, so that queries and requests can be addressed in a timely and consumer friendly manner. Conclusion: The maintenance of an efficient Solid Waste Management system requires an enormous investment of material, financial, technical, human and other resources. The cooperation and support of all stakeholders cannot be underestimated. A concerted and coordinated effort from all sectors i.e., government, public and private, as well as the entire community must be encouraged and nurtured for the benefit of all.
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Key Words: The main points of this presentation will be presented under the following headings: Introduction Objectives Methodology Constraints & Obstacles Results Conclusions Introduction Solid Waste Management is a major problem in St.Vincent and the Grenadines. It presents a serious threat to the health of the public and, our delicate ecosystems which impacts negatively on the country’s economy. In an effort to address the situation, the Government participated in the OECS Solid and Ship-Generated Waste Management Project. This Project entails the development of Sanitary Landfills, the closure of dumpsites and the provision of equipment and other facilities necessary for the proper management Solid Waste. The dispersed nature for the responsibility for Solid Waste Management (3 agencies were involved), proved to be a major impediment to an efficient system, as was the lack of equipment, facilities, and concerted education/awareness programmes. To correct this situation, government in November 1999, established a Solid Waste Management Unit (SWMU) within the Central Water & Sewerage Authority (CWSA). This Unit was charged with the following: Ø Ø Ø Ø Ø
Closure of existing dumps and the development of sanitary landfills Provision of facilities at major ports for accepting ship generated waste Development and enactment of new legislation Public education, information and community outreach The development of a waste diversion programme using the 4Rs Approach.
The Unit has effectively addressed and continues to implement activities in order to accomplish its objectives. The new Solid Waste Act was passed in the House of Assembly in December of 2000, one of two landfills on mainland St.Vincent has been completed, two rural dumps as well as two thirds of the main Arnos Vale dump have been closed. The remaining one third of the Arnos Vale site has been converted to a landfill.
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Arnos Vale Before
Arnos Vale After
Equipment including the collection vehicles is in use, and the public education/awareness programme is ongoing. Within the last two decades, there has been enormous challenge to maintain what pure and natural environment we have left. An increasing variety of environmental challenges have surfaced worldwide. These include water and air pollution, deforestation, climate change and Solid Waste Management. This paper seeks to address the challenges in Solid Waste Management in small countries such as St.Vincent & the Grenadines, and how we can utilize existing strategies and resources more effectively and efficiently to correct some problems, and confront the presenting challenges, According to Gerwig and Permanente, in an article entitled Waste Management White Paper: “Waste Management” may seem a lowly topic when there are many environmental issues that garner more excitement, or fear.” The fact is, however, that there are no environmental issues more fundamental to building and sustaining environmental responsibility and good health, than effective waste management. I cannot impress upon you more, the urgency of effectively managing our Solid Waste. Proper management of waste impacts importantly on many of these environmental issues/problems, as it does on every other aspect of our being. If we were to continue to dump in our rivers, and pollute the land with Styrofoam and plastics, it will eventually reach the sea polluting the waters and the fish we eat, thus entering our food chain. This means that the same discarded waste will return to us in a far more undesirable way. The effective management of Solid Waste will ensure a safe, healthier environment. The benefits will be seen in the jobs provided in the industry itself, a cleaner, more appealing environment for us to enjoy, as well as for the visitors to our respective countries. Earlier in my presentation I shared some of the consequences of ineffective management of Solid Waste; thus given the changes in consumption patterns and the amount of waste being generated, and the public outcry for better and improved methods of managing waste, Service Providers are left with little choice. It behooves us to utilize all resources necessary
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to confront and overcome the challenges presented to us in order to achieve positive outcomes.
It is paramount that as Service Providers, we fully comprehend the basic concerns, issues and needs of the consumer if we are to establish and nurture the partnerships necessary for working together to arrive at positive solutions to resolving our common problems. We must understand that infrastructural investment alone is not enough. We need to focus on attitudinal changes. We need to convince stakeholders that benefits will be long term. We need to demonstrate that small countries with limited resources can have effective and efficient Solid Waste Management systems by working together and sharing resources. Evidence from successes in developed countries show, that despite all of their financial and other resources, they too have realized the benefits of partnerships to proper Solid Waste Management; and are beginning to utilize that approach. Objectives This approach should result in: 1. Increased consumer knowledge and confidence in us the Service providers 2. A more educated public regarding Solid Waste Management programmes, so that they will be able to have input into, and contribute to the design and structure of such programmes. 3. Consumers who are involved in the development of new projects within their communities taking part in the planning and ownership of these projects. 4. A change in attitudes of the consumer, making them more responsible in the disposal of solid waste. 5. Utilization of the 4Rs Approach by the vast majority of consumers 6. Reduction in the amount of waste going to the landfills as a result of established entrepreneurships in recycling and composting
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Methodology In order to achieve these objectives we need to employ an eclectic approach. We must establish and maintain partnerships and various networks both internal and external. No one method or approach achieves the desired outcomes. There needs to be Quality Assurance Surveys (including customer satisfaction), Community Outreach education Programmes, as well as School based education Programmes, The Solid Waste Management Unit of St.Vincent and the Grenadines has utilized and continues to utilize all of these methods and more including in service training for the private sector. Customer Quality Survey Shortly after it’s establishment in 1999, the Unit with the aid of 30 specially recruited, hired, and oriented young people, conducted a Customer Quality Survey. The objectives of that survey were as follows: 1. To collect baseline data which would be used for further evaluation and improvement of the Solid Waste Management system 2. To obtain information regarding the level of satisfaction of the population, with respect to the Solid Waste Management services 3. To elicit recommendations and proposals for inclusion into a National Strategic Plan for Solid Waste Management as it relates to the Public Awareness and Waste Collection Systems Then survey questioned a total of 2386 people representing 2006 Households and 380 businesses from the 15 constituencies in St.Vincent & the Grenadines. Findings: Plastics were the leading items of waste produced, followed by kitchen and garden waste. We realized from the data that there was a need for more education on Solid Waste Management. In addition more school outreach programmes should be put in place, and all media should be utilized to the fullest. A Profile of each constituency was developed and the collected data was used in designing programmes, so that specific needs would be identified and addressed. The Unit will evaluate its programmes at year-end, and use that data to measure their effectiveness. Community Outreach Community Consultations and Focus Group Discussions have been tremendous, we will continue to use these approaches to solicit ideas and suggestions from consumers and other stakeholders in communities where we will be working. These methods/approaches must never be underestimated. They offer our customers an opportunity to become part and parcel of the planning process. They allow communities, businesses, institutions as well as individuals to apply and utilize their creative skills in: (a) Identifying the needs of the related sector, be it a rural or urban community (b) Drafting policies and (c) Designing programmes for proper Solid Waste Management including waste reduction, thus allowing them to be partners in resulting projects and programmes. An example of how the data is used, is reflected in our focus on the 4Rs approach and in particular composting. The results of the Customer Quality Survey showed that on average, 17 pounds of waste was produced per household, per week, forty seven percent (47%) of this waste came from the kitchen and garden. The emphasis on educating communities on Composting is to prevent such material from ending up in the landfill. When communities
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realize the benefits of the humus yielded from composting, our credibility will be enhanced, and links to the community will be strengthened. Community outreach and educational sessions are also invaluable in reaching residents. They assist in capacity building, and establishing cross – sectoral teams at the community level. This will ensure the appropriate interventions are implemented and hence easily sustained. These community workshops are very often held outside the regular working hours, and on weekends. They should be designed to accommodate the schedules of the participants, culturally sensitive. These Sessions should be kept simple, enlightening, and allow for audience participation. Collaboration with Business Sector Involving the business sector via employee in-service training programmes, sponsorship for special projects, and the encouragement of privatizing recovery/recycling projects will further enhance our efforts. In SVG, our working with local businesses is a priority. Shortly after the establishment of the Unit in 1999, meetings were organized with as many sectors as possible to discuss matters of mutual interest. The Unit also offers free of cost, a special training programme on Solid Waste Management for workers on the job. This was designed to reach those persons who because of distance between work and home find it difficult to attend community consultations. It also provides a unique opportunity to demonstrate waste reduction techniques at the workplace, which can translate into reduced operational costs. Since plastic was identified as the leading waste in the country the involvement of the business sector is crucial. Almost all of our business houses with few exceptions use plastic wrapping. Many consumer goods come in plastic containers or are made from plastic. During workshop sessions particularly with management, issues of re-exportation of plastic, working with suppliers to reduce excess packaging, and use of paper vs. plastic is usually discussed. The required change seems distant, however the Unit will collaborate with groups and agencies with similar interests including the Ministry of Trade to find solutions to these challenges. During these sessions, as in the community outreach sessions, the audience is made aware of opportunities for waste diversion including recycling. Available information on regional recycling concerns is also shared. In an effort to keep in contact, the business sector is kept abreast of the developments in solid waste management through the Unit’s quarterly magazine/newsletter “Trash Talk”, made available to them through the Chamber of Industry & Commerce. Collection & Disposal Service It is imperative that we also provide an efficient and reliable collection and disposal service, and good information management systems, so that queries and requests can be addressed in a timely and consumer friendly manner. In St.Vincent and the Grenadines this presented the greatest challenge, after attitude change, to the Solid Waste management Unit. The reasons for this were many and varied, the major one being, an inadequate and unreliable fleet of collection vehicles. These vehicles were subject to frequent breakdowns resulting in a disrupted collection schedule. Although staff members spent a great portion of the workday answering calls and trying to solve problems,
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the situation created a temporary loss of credibility for the Unit; it did as well, in a small way, erase the success of other activities that were being consecutively undertaken at the time; while at the same time highlighted the seriousness of our waste generation problem. School Outreach Instilling proper attitudes at an early age is priceless in any situation. A school outreach programme therefore could not be left out. The Unit solicited the assistance of the Ministry of Education in this regard for training of teachers, and for permission to establish special projects in select schools. The Unit also developed a special training manual with 8 lessons. The lessons are designed to get the students involved and have fun while learning. The Unit has also developed for children, bookmarkers with Solid Waste messages, as well a colouring book with a story that is designed to reach both children and adults. The idea is that adults who read the story to children, who cannot themselves read, will get the message at the same time. The Unit’s newsletter is also sent to all schools. Currently composting projects are being carried out in 4 rural secondary schools. It is hoped that these will form a base for educating the wider community about composting. Constraints §
§ § §
Negative attitudes of the population and bad habits regarding Solid Waste Management. Many people see the responsibility of managing Solid Waste as the Government’s, thus they continue to litter and dump over banks, in rivers, in drains and on vacant lots, and to put waste out on the streets before collection day. Solid Waste Management Act which does not give the Unit the authority to issue tickets or to use measures within its direct control to deal with offenders. Lack of support in some instances, from relevant agencies and government departments Need for more human and material resources
Results v Involvement of the business sector in public education efforts, including the sponsorship of special events and projects, including promotional walks, billboards and media programmes v Although the anticipated support was not forthcoming from the Ministry of Education for all of the Unit’s initiatives, several teachers have on their own requested the manual for use in their classes, and the unit has established a working relationship with several schools, both primary and secondary.
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v Increase in requests for community workshops, reports of illegal dumping, and assistance for community clean up activities v Cleaner communities Conclusions In conclusion, there are some areas that need to be focused on if we are to achieve the expected outcomes. Ø An effective and efficient public information system be established and maintained. In St.Vincent and the Grenadines we have a hotline dedicated to customers queries, complaints and reporting unlawful activity. Ø There must be on going education/awareness programmes for all sectors of the society. This is critical since education is needed to influence behaviour change, build capacity and effect community involvement at all levels. Ø A reliable, efficient collection and disposal system must be provided, with contingency planning in the event that a truck breaks down. Once this is in place complaints become less, and the public becomes more willing to support activities and initiatives. Ø An annual customer quality survey should be an integral part of our overall plan, and the data gathered used to spot trends and design projects that will meet the needs of our target population.
Bibliography Waste Management White Paper - Author Kathy Gerwig, Kaiser Permanente Author: Valerie Beach, The Solid Waste Management Unit/CWSA, P.O Box 363, Kingstown, St.Vincent & the Grenadines Tel: (784) 456-2946, Fax: (784) 456-2552, E-mail
[email protected] or
[email protected].
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Human Resources and Development as a Value-Added Strategic Business Partner by Gloria Glidden, BBA, CPA Deputy Director, Water Authority – Cayman
“What are you doing?” Inquired the policeman of the drunk crawling on the pavement under the glow of a lamppost. “I am looking for my quarter,” came the reply. “Where did you lose it?” asked the officer helpfully. “I dropped it over there by the payphone,” retorted the drunk. Incredulous, the officer asked, “Then why are you looking in the middle of the street?” “Because there is more light over here,” he replied with his nose nearly to the ground. (Author unknown) Abstract The Human Resources and Development (HRD) function in any organization should be that of a Value-Added Strategic Business Partner. The most effective tools that the HRD function can leverage to produce maximum impact on the overall organizational performance and establish their role as a strategic business partner are management of the organization’s culture and structure; defining and designing strategies for staffing, training and development; performance management, rewards and recognition. These key areas should fall within the realm of the Human Resource (HR) function. HR must take the lead by formulating strategies and designing programs that will encourage the creation of economic value to the organization. By asking for, measuring, recognizing and rewarding behavior that effectively leverages economic value the HR function becomes a vital contributor to organizational success. To successfully utilize these tools the role of the HR function shifts from the traditional transactional and tactical role to assisting management with strategies, policies and practices to ensure that the goals and objectives support the overall mission of the organization. As a result, HRD should understand the business needs of the organization and make every effort to recruit, train and retain employees that will ensure that the business needs are met. HRD should also have the expertise to evaluate and measure HRD programs and processes and provide for rewards and recognition mechanisms. This paper explores these key factors and identifies how HRD as a strategic business partner creates economic value beyond the traditional tactical and transactional role with particular references to the challenges facing the utility industries, especially in the Cayman Islands.
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Employees are the organization’s most important assets and studies have shown that there is a correlation between the effectiveness of the HRD function and the generation of economic value to the business. Key Words Strategic Business Partner, Economic Value, Business Needs, Return on Investment (ROI), Training and Development. Introduction Dynamic forces are transforming societies worldwide and requiring the utilities industry to rethink the way business is done. The dawn of the global economy has raised competition to new heights. In underdeveloped countries the population levels are rising, causing a strain on the existing resources and opening new markets for goods and services. The Internet has revolutionised many aspects of business (Shorney, 2000). Once a tool reserved for scientific and academic exchange, the Internet has surfaced as an appliance of every day life, accessible from almost every point on the planet and creating the world of e-commerce. With new technologies, stricter regulations, changing workforce demographics and requirements, the need for increased operational efficiencies, and the emergence of the environmental conscious movement are all developments that are affecting every aspect of the utility industries from management and operations to consumer information. In addition to these challenges, some utilities are faced with extensive growth while others face the challenge of replacing a decaying or inadequate infrastructure. The rapid growth in the economy of the Cayman Islands over the years has brought about a lot of socio-economic pressures. The limited size of the Caymanian labour pool results in importing of foreign labour to support businesses. With about 58% of the labour imported (Cayman Islands Census, 1999), this poses many challenges to businesses and to the social harmony of the islands. The field of HRD is in transition as well, in conjunction with the increasingly competitive business environment. HRD professionals must continue to streamline organizational functions, while maximizing individual competencies. The HRD process involves teamwork and support from all levels of the organization, integrating HRD into the business environment and culture as never before. In light of the many obstacles the utilities industry is facing, it is evident that organizations must keep an eye on local business conditions while maintaining a global perspective. They must move quickly to incorporate advances in technology. They must find ways to motivate and hold on to superior employees in the workforce. They must improve communication, service, and value for their customers. Today, many utilities are discovering a need to reinvent the HR function. What is necessary is for the HR function to expand its focus beyond its traditional transactional and tactical
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roles to that of helping senior and line managers align HR practices, processes, and strategies with the business needs and focus on HRD as a value-added strategic business partner. According to Greene (2001), when all of an organization’s assets go home on Friday and are free not to come back on Monday, investment analysts wonder what the organization really possesses. As many organizations see their market value exceed ten times their “book” value they struggle to identify ways of effectively managing this “goodwill” item that accounts for the majority of their value. Investment analysts currently base over one third of their valuation of organizations on intangible “assets” or “capital” that the accountants do not enter into their books, which sends the message to management that these things must be managed. The definition of HRD given by Richard A. Swanson (Swanson, 1999) is very relevant in today’s context, “HRD is a process of developing and/or unleashing human expertise through OD [organizational development] and personnel training and development for the purpose of improving performance of the organizational, process and individual or group levels. The process of HRD is made up of five core phases including analyze, propose, create, implement and assess.” Employees are the organization’s most important assets and studies have shown that there is a correlation between the effectiveness of the HRD function and the generation of economic value to the business. Therefore, it is necessary to look at the following key strategies and programs that explore how the HRD function transforms from a transactional and tactical oriented role to a strategic partnering role providing measurable value-added services: · · · · ·
Defining and Designing the Organizational Culture and Structure. Strategies and Programs for Recruiting, Training and Development. Strategies and Programs for Employee Performance Management. Strategies and Programs for Rewards and Recognition. Strategies for Measuring the Impact of Human Resources.
Defining and Designing the Organizational Culture and Structure In examining the culture of an organization, it is necessary to take a macro perspective and examine the type of environment and culture where the organization is operating. In the Cayman Islands, for example, with the restriction on the labour pool resulting in about 58% of the workforce being imported (Cayman Islands Census, 1999) the islands are facing many multicultural socio-economic pressures. For example, the conditions that one individual may agree to work under from one country may be different from the conditions expected of an individual in another country. Therefore, it becomes necessary to balance the value of importing of labour against the social harmony. Even though in most cases the imported labour is necessary and does positively impact the bottom line of an organization, it can cause a strain to the social harmony of the country. Therefore, the HRD function plays a vital role in growth and prosperity at all levels.
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Culture and organizational design frequently do not fall within the domain assigned to the HR function, however there are strong arguments that they should. According to Greene (2001), too many organizations let their culture happen, rather than consciously shaping it and continually reassessing it for effectiveness and appropriateness. Rarely is any function responsible for making decisions relative to organizational design, leaving this critical area to people with no training. It is therefore suggested that HR strategies, programs and processes are the most powerful tools to drive effective performance management (Leonard 1998; O’Dell & Grayson 1998). There is generally no position or function charged with defining, evaluating and shaping the organizations’ culture, HR is therefore the most logical function to assume this responsibility, guided and supported by executive management. Defining the culture, assessing its effectiveness in light of the organizational context, and formulating strategies for reshaping it if it is not optimal given the organizational objectives and priorities naturally fall within the realm of HR. Selecting, developing and rewarding people in a manner that facilitates the creation of the desired culture is the key to getting the job done well, and these strategies and programs are shaped by HR. Direction from executive management in the form of a clear vision and articulated values is also needed, but it will be the HR strategies and programs that will set the stage for developing and maintaining an appropriate and effective culture (Green, 2001). The HRD function should assist management with strategies, policies and practices to ensure that the goals and objectives support the overall mission of the organization. The HR function should also have an HR business plan that outlines the goals and the strategies for achieving the goals as this enables the HR function to go beyond the day-to-day tasks to see the larger purpose of the HR function and how it integrates with the overall business needs of the organization. The absence of a business plan can leave an HR department with a lack of vision and direction. In the Cayman Islands, some of the larger organizations like some of the utilities are encouraged to file their business plan to the Cayman Islands Immigration Board. The business plan should outline the organization’s planned growth with an emphasis on human resource growth to identify where the company is going in the short, medium and long term and its staffing needs to get there. For example, if the organization requests the need for four work permits then the organization has to also show that four Caymanians are in place to be trained for those positions and therefore, you can request those permits for a period of time that is sufficient to train the Caymanians for those posts. This streamlines the process for both the organization and the Immigration Department. As long as organizations follow and update the plan, concerns and unknowns are eliminated as to whether the work permit requests will be granted or not as well as satisfy the country that training of locals is taking place. This helps to eliminate the glass ceiling. Businesses to an extent will no longer have to worry as to whether a work permit in the future will be approved once it is in accordance with the approved business plan. The expatriate worker will also be aware of what is expected of him/her and the period of time he/she is expected to be working away from home.
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A strategic partner must be very knowledgeable and have a “big picture” view of the organization’s business and its needs as well as a close relationship with the key leaders of the organization to align developmental efforts with the organization’s strategic goals. It is not possible for everyone in the HR function to play the part of a strategic partner, but rather only some as HR functions must continue to deliver transactional and tactical services and organizations need to have employees on hand to perform this type of work. Strategies and Programs for Recruiting, Retention, Training and Development HRD as a strategic partner should make every effort to recruit, train and retain employees that will ensure that the business needs are met. Business needs constantly change over time, therefore it is very important that no matter how the HRD function is organized it needs to be robust and responsive to what is happening at all times. Recruiting & Retention Perhaps the greatest challenge to the organization today is attracting and retaining superior employees. Businesses must compete vigorously to attract qualified employees, who are in increasingly short supply and even greater demand. Therefore, business leaders worldwide have attempted to address these challenges and create new definitions of organizational excellence, to delineate the characteristics that will ensure business success in the new millennium. In many cases, especially here in the Cayman Islands, utilities monopolise the market and as a result specialised training in the particular fields are less attractive to potential quality employees. For example, someone with a degree in accounting will have more career choices and mobility than someone in a very specialised field in the utility industry. Therefore, it is essential that the HRD function in utilities constantly focus on innovative ways to attract and retain high calibre, superior employees. A Passion-Driven Organization One strategy to attract and retain top talent according to Chang (2001) is to have a passion plan at work that links process and passion to align employee commitment, capability, and satisfaction with organizational performance and success. Chang defines passion “as personal intensity, or the underlying force that fuels our strongest emotions.” It is the passion-driven organizations that appeal to the superstars of the job market. Motivated and energetic individuals are attracted to environments where their individual passions will be allowed to thrive. They are eager to commit themselves to the shared passion that defines the organization. In this respect organizations that exude a sense of excitement, that are driven by a strong emotional connection to their enterprise, have a distinct edge over those that do not. Talented employees actually seek them out, not the opposite. Passion also builds loyalty as employees remain loyal through the ups and downs of the organization when they are committed emotionally to the success of the business, conversely, when the relationship between employer and employee is based on money loyalty is not an issue because the relationship ends as soon as a better price or more attractive salary appears.
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When leaders, employees, and customers share a core passion, they stand on common ground and stick together even when things get difficult (Chang, 2001). Passion heightens performance as increased energy, focus, and creativity all contribute to heightened performance. Passion drives improvements in both the quality and quantity of work performed as the employees of the organization not only care about what they are doing but they are constantly motivated to do more and do it better (Chang, 2001). Workplace Flexibility Some specific workplace practices are offering flexible work arrangements, encouraging teamwork and cooperation, providing equal benefits, having high employee satisfaction, and generally having a family type but yet professional atmosphere in the office. According to The Global Business Responsibility Resource Centre (Internet Source, 2001) a growing body of evidence points to the connection between work-life programs and bottomline performance measures such as productivity, turnover, recruitment, and retention. Research has also shown that work-life initiatives have a favorable impact in such areas as employee satisfaction, job commitment, and stress levels. Several studies have identified links between work-life benefits and overall employee performance, loyalty, and satisfaction. For example, a 1997 survey of more than 150 executives conducted by the Whirlpool Foundation, Working Mother magazine and Work & Family Newsbrief found a link between 40 work-life programs and practices (including flexible work arrangements, childcare and eldercare, employee assistance programs, and financial assistance) and 16 different business results (including improved productivity, reduced absenteeism and turnover, enhanced employee satisfaction and morale, and decreased health care costs). Therefore, it is clear that organizations must recognize the relationship between employee’s personal lives and their careers. Flexible work arrangements help high performing workers achieve the proper balance. In turn, the organization maximizes a return on the investments made in its employees. With the rapid global changes, utilities that are more flexible and adaptive in their approaches are more likely to thrive when threatened by increased competition, technological advancements, and other global forces. Communication Communicating effectively with employees and always keeping them abreast of issues and events currently taking place within the organization, such as e-mail, newsletters, etc. is the key to generating economic value as well as giving employees the opportunity to offer ideas and suggestions to senior managers, and sharing financial information with employees. According to Nelson (1999), information is power, and employees want to be empowered with the information they need to know to do their jobs better and more effectively. More than ever, employees want to know how they are doing in their jobs and how the company is doing in its business. Organizations should open the channels of communication to allow employees to be informed, ask questions, and share information.
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Training and Development The quality of employees and their development through training and education are major factors in determining long-term profitability of an organization. If an organization hires and keeps good employees, it is good policy to invest in the development of their skills, so they can increase their productivity. The workforce should therefore be provided with training and development for their respective core competency areas. A mistake that many organizations make is to only consider training for new employees, however ongoing training for current employees helps those employees to adjust to rapidly changing job requirements. In the Cayman Islands, for example, the issue of immigrant workers poses another challenge for the HRD function. In most cases, professional and skilled workers are more prepared academically than the local worker and have the required experience. This is due so such persons having exposure and benefiting from larger developed countries where competition for jobs, scholarships, etc. is tough. As a result, companies are less motivated to invest in training locals because it is easier and more cost effective to import a labour force that already has the required education and experience. Therefore, it is the function of HRD to recognize the long term value to the organization, especially utilities where training is very specialised, and to the country overall to make the investments in training and development of the local workforce as well as putting proper succession planning in place. Many utilities, as mentioned earlier, carry out business as a monopoly and as such may be tempted to become comfortable and complacent with the service provided to customers as well as training and development of staff. It is important for the HRD function to encourage training and development in the utility industry to ensure that the best service is provided to customers and, at the same time, to attract and retain the best employees. Therefore, by emphasizing the growth and development of personnel an organization will: ·
Ensure that there are adequate replacements readily available for personnel who may leave or move up in the organization.
·
Enhance the company's competitive position by building a more efficient, effective and highly motivated team, which also improves employee morale and reduces employee turnover.
·
Enhance the company's ability to advance in technology by having trained and knowledgeable staff.
By providing training and development to employees in their respective core competencies, the employee frequently develops a greater sense of self-worth, dignity and well-being as they become more valuable to the firm and generally they will receive a greater share of the financial gains that result from their value added services. These factors give them a sense of
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satisfaction through the achievement of personal and organizational goals that ultimately reflects positively on the organization’s bottom line. Strategies and Programmes for Employee Performance Management One of the greatest tools in any organization is the employee performance appraisal. This tool assists management in helping poor performing employees improve, making decisions about terminating employees who perform below acceptable levels, for recognizing and rewarding those employees that perform at acceptable levels and above, and to set compensation levels. According to Greene (2001), it is important to define performance using criteria that encourage employees to turn capabilities into action. The most commonly used performance criteria are productivity, quality of work and dependability. Although these criteria will promote individual effectiveness, they overlook the contributions of an individual to making others and the unit more effective. Increasingly, organizations are adding additional factors to the performance appraisal that measure “contribution to the effectiveness of others” and “contribution to unit/organizational effectiveness.” When contributions to the effectiveness of others are being measured the use of multi-rater assessment may become desirable. Having the co-workers, subordinates, customers and superiors all evaluate performance can provide a multi-perspective, broader view of how well the employee helps others to be more effective. It also lets the employee know that the views of these parties are valued and that they are considered in the evaluation process (Greene, 2001). Strategies and Programmes for Rewards and Recognition According to Nelson (1994), the results of a survey of employees by the Council of Communication Management confirm the common wisdom that recognition for good work is the top motivator of employee performance. “While money is important, what employees’ value most today is recognition by their supervisors of a job well done.” The three categories of recognition are as follows (Nelson, 2001): 1. Formal Recognition (for example, events and programs). 2. Informal Recognition (for example, tools and activities). 3. Day-to-Day Recognition (for example, practices and techniques). Nelson, Good, and Hill (1997) stipulate that the best employee reinforcers are immediate, sincere, specific, and positive. Ø Be immediate. Positive reinforcement is much more effective when it comes soon after the desired behavior is displayed. Ø Be sincere. Praise is important, however if it lacks sincerity it defeats the purpose.
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Ø Be specific. Avoid generalities and use the details of the achievement. employees know specifically what to do again.
The
Ø Be positive. Managers tend to undercut praise with a concluding note of criticism. The corrective feedback should be done at another time. Study after study has shown that praise and recognition tend to build employee loyalty. People want to feel that what they do makes a difference. Money alone does not do this; personal recognition does. Employers often fail to realize that some of the most effective things they can do to develop and sustain motivated, committed employees cost very little or nothing at all (Nelson, 1999). Strategies for Measuring the Impact of Human Resources Recently a trend has developed toward justifying the expenditures for and the existence of the HR function. HR departments and programs have become an element of the organization’s profit equation to be minimized as a cost and maximized as a value-adding component of firm strategy. Some have characterized HR departments as bureaucratic wastelands and suggested doing away with them (Stewart, 1996). Consequently, HR practitioners have become preoccupied with demonstrating the value of the HR function, particularly through showing its impact on firm performance (Pfeffer, 1997; Ulrich, 1997). Since the 1960s, according to Phillips, Stone, and Phillips (2001), several approaches have been used for the measurement and evaluation of human resources. The following tables show how these measurement approaches have changed over time, the relative cost, and the relative value of the information (from the perspective of the client): Table 1 identifies the early approaches that are still being used by many organizations however other approaches are also being incorporated as organizations work toward more effective measurement processes (Phillips, et al 2001).
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Table 1 Early Approaches, during early 1960s – late 1970s Approach
Description of Approach
Measurement Focus
Relative Cost
1. HR Management by Objectives
The evaluation process of measuring progress toward HR performance objectives. With this approach, the HR department develops specific objectives and evaluates performance against those objectives.
Goal Setting for HR Performance Measures
Low
Relative Value of Information Moderate
2. Employee Attitude Surveys
These are surveys that attempt to link employee attitudes to organizational performance.
Attitudes/ Perceptions
Moderate
Moderate
3. HR Case Studies
This approach presents results in a case study format to selected audiences and are developed using data about HR performance, reaction from individuals, or interviews with participants involved in HR programs or services.
Qualitative Description with Data
Low
Low
4. HR Auditing
A human resource audit is an investigative, analytical, and comparative process that attempts to reflect the effectiveness of the HR function. It undertakes a systematic search that gathers, compiles, and analyzes data in depth for an extended period, usually one year, instead of with daily formal and informal reports.
Efficiency/ Existence of Practices
Low
Low
(Table adapted from Phillips, et al 2001)
According to Phillips, et al (2001) the approaches in Table 2 are being used regularly by most progressive organizations:
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Table 2 Solid, Value-Added Approaches, during late 1970s – late 1980s Approach
Description of Approach
Measurement Focus
Relative Cost
Relative Value of Information
5. HR Key Indicators
Key measures are developed that reflect the major efforts of the HR function and in some cases, these measures are linked to organizational performance. A set of quantitative measures is used such as absenteeism, turnover rate, etc.
Program/ Function Performance Measures
Moderate
Moderate
6. HR Cost Monitoring
In this method HR costs are developed and used in comparison with cost standards. For example, cost per hire or orientation cost as these relate to employment.
Program/ Function
Low
Low
7. HR Reputation
Some HR professionals suggest that the effectiveness of the HR function should be judged by feedback from those it is designed to serve, often referred to as constituencies or clients.
Attitudes/ Perceptions
Moderate
Moderate
8. Competitive HR Benchmarking
A few organizations developed key measures that represent the output of the HR function. The measures are compared with measures from other organizations regarded as having best practices within a given industry.
Performance Measures/ Practices
High
High
(Table adapted from Phillips, et al 2001)
Although some organizations have made progress with these techniques, as described in Table 3 they are still in the developmental stage within the vast majority of organizations (Phillips, et al, 2001)
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Table 3 Leading-Edge Approaches, late 1980s – early 2000s Approach
Description of Approach
Measurement Focus
Relative Cost
9. Return on Investment (ROI)
Probably the most convincing approach to HR evaluation is to compare the cost of the HR programs with the benefits derived from them. This approach is built around the basic financial equation, earning divided by investment, or net benefits divided by costs.
Benefits vs. Costs
High
Relative Value of Information High
10. HR Effectiveness Index
A few organizations have attempted to develop a single composite index of effectiveness for the HR function
Multiple Key Indicators
High
High
11. Human Capital Measurement
This concept attempts to place a value on employees as assets in an organization and to measure improvements or changes in these values using standard accounting principles. It is an extension of the accounting principles of matching cost and revenues and of organizing data to communicate relevant information in financial terms. Human resources are viewed as assets or investments of the organization.
Value of skills/ Capabilities/ Performance of Employees
High
Moderate
12. HR Profit Centre
This concept requires a shift from the traditional view of the HR department as an expense centre in which costs are accumulated, to a view of HR as an investment that can achieve a bottom-line contribution and, in some cases, actually operate as a profit center.
Profit Contribution of Programs/ Services
High
High
(Table adapted from Phillips, et al 2001)
These twelve approaches set out in Tables 1 to 3 provide an array of useful tools to help the HR department develop a comprehensive strategy to show its contribution. However, according to Phillips, et al (2001) of the twelve approaches, the ROI process provides a balanced approach to measuring the bottom-line impact of HR initiatives. In addition, most HR staff members share a concern that they must eventually show a return on the investment in their programs. Otherwise, resources may be reduced, or the function as a whole may lose credibility with the organization.
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Human Resources and Development as a Value-Added Strategic Business Partner
Conclusion Like the drunk in the middle of the street, HR practitioners have spent much effort looking where there is already light; however the HR function must look beyond the light, beyond the traditional tactical and transactional role and assist management with strategies, policies and practices to ensure that the goals and objectives support the overall mission of the organization. HR practitioners must utilize the most effective tools that the HRD function can leverage to produce maximum impact on the overall organizational performance and establish their role as a value-added strategic business partner and must understand the many approaches to measuring the impact on human resources as there are many gaps and thin spots where much more empirical work needs to be done. However, by assuming the responsibility for the end objective of creating economic value for the business, HR can integrate and align the strategies and programs that will facilitate the success of the organization. References Cayman Islands Census (1999). Report of the Cayman Islands 1999 Population & Housing Census. Chang, R. Y. (2001). The Passion Plan at Work: Building a Passion-Driven Organization. San Francisco: Jossey-Bass. Global Business Responsibility Resource Centre (2001). Internet Source. Greene, R. J. (2001). Building Social and Intellectual Capital: Critical Challenge/ Opportunity for Human Resources. Society for Human Resource Management. August 2001. Leonard, D. (1998). Wellsprings of Knowledge. HBS Press. Nelson, B. (1994). 1001 Ways to Reward Employees. New York: Workman Publishing Company, Inc. Nelson, B. (1999). Cost Ways to Build Employee Commitment. Nelson Motivation, Inc. 1st December. Nelson, B., Good, L., and Hill, T. (1997). You Want ToMAYtoes, I Want ToMAHtoes. Training Magazine. June issue. O’Dell, C. & Grayson, C. (1998). If Only We Knew What We Know. Free Press. Phillips, J. J., Stone, R. D., and Phillips, P. P. (2001). The Human Resources Scorecard: Measuring the Return on Investment. Massachusetts: Butterworth-Heinemann
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Pfeffer, J. (1997). Pitfalls on the Road to Measurement: The Dangerous Liaison of Human Resources with the Ideas of Accounting and Finance. Human Resource Management, 36(3), 357. Shorney, F. L. (2000). Forces Transforming the Water Business. Jour. AWWA, 92(1), pp. 88-93. Stewart, T. (1996). Taking on the Last Bureaucracy. Fortune. 133:1, 105. Swanson, R. A. (1999). HRD Theory: Real or Imagined, pp. 2-5. HRD International, Vol. 2, No. 1. Ulrich, D. (1997). Measuring Human Resources: An Overview of Practice and a Prescription for Results. Human Resource Management, 36(3), 303. Author: Gloria Glidden, BBA, CPA Deputy Director, Water Authority – Cayman P.O. Box 1104 GT Grand Cayman Cayman Islands Tel: (345) 949-6352 Fax: (345) 949-0094 Email:
[email protected]
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy) by Bill Melendez, RAMAR LLC Introduction Automatic Meter Reading (AMR) is becoming a reality in Latin America. For many, this new approach to meter reading poses challenges in the areas of understanding the technology and the process essential for successful implementation. The issues that AMR brings to the decision maker require a thorough analysis of what the utility’s needs are and what AMR has to offer towards resolving those needs. This paper deals with the process of assessing and planning AMR deployment for successful project management. There are many AMR implementation schemes based on the technology being used. These technologies place functional constraints due to product specifications and limitations. The decision maker must realize and understand that, due to these limitations in product functionality, it may be necessary to implement various technologies simultaneously in order to accomplish the goals of meter reading. In some cases, methodology and not AMR may be the best solution. Because AMR technologies differ as to functionality, implementation, and sustainability, it becomes imperative that utility managers or decision makers first assess the need for AMR. An assessment can be a simple statement expressing what the need is, or it can be an extensive document outlining every facet of the utility’s meter reading requirement. In small utilities, the need assessment can also become the feasibility study and the cost benefit analysis report. In larger utilities, with multiple departments, the need assessment can be a stand-alone document before the feasibility study is considered. The suggested format for determining whether to implement AMR or not is: · · · ·
Step One: Conduct a Need Assessment (NA) Step Two: Conduct a Feasibility Study (FS) Step Three: Conduct a Cost Benefit Analysis (CBA) Step Four: Conduct a Request For Proposal (RFP)
Need Assessment The first step towards evaluating an AMR implementation strategy is to draft a need assessment. This is the most critical part in the entire process since it is the basis for justifying procurement and delineates the scope of investment. The assessment should clarify what need(s) the AMR solution is addressing. It should also identify short-term and longterm needs, normally by departments or sections. The need assessment’s focus is to identify needs and assign value to each. Value can include tangible and intangible benefits that provide a true picture of costs or savings as a direct result of selecting one AMR system over another as compared to having no system at all. Capturing value can be a subjective exercise since each individual in the approval process
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sees value differently. The best approach is to design a matrix with a number scale relating level of importance (priority) to each need. The final step would be to assign cost values in terms of man-hours or material costs. The following chart illustrates various needs based on what utilities experience in providing services to its customers. Each provides a cost savings associated with either performing tasks or processing tasks. The overall return on investment can be determined using the four categories:
IDENTIFYING VALUE VALUE ITEM
CATEGORY
MAN-HOURS
MATERIAL COSTS
Improve safety of me ter reade rs
Improved Human Resource Management
Time manageme nt improvements (efficient use of employee’s time and limited resource s) Re duce insurance rates and liability factors/insurance claims Improve productivity and reduce staff
100% accurate and equitable monthly billing
Improved Customer Service
On-demand mete r reading for verifying custome r billing Delinquent accounts identified sooner (don’t have to wait until the route is read or manually keyed into database) Improve response time to customer complaints Improve customer’s history of usage
Reduce misre ads or re-reads due to human error
Improved Meter Reading Process
Eliminate e stimates due to personnel shortage or weather pre vention Tamper and fraudulent use notification Water or gas loss calculations (water and gas meters) Le ak detection (wate r and gas mete rs) Reve rse meter notification
Improved Logistics & Maintenance Management
M eter reading data can be used for scheduled maintenance and life expectancy of mete rs Outage information and peak demands (ele ctric) Leak dete ction (water and gas) Forecasting usage
Figure 1. Identifying Value in Man-Hours and Material Costs Identifying the various needs requires understanding how they relate within the work environment and whether they are procedural or resource related.
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
Procedural needs are defined by policies and procedures/processes while resource needs mandate identifying equipment, time, and personnel requirements. Clayton Christensen, author of The Innovator’s Dilemma: When New Technologies Cause Great Firms to Fail, adds a third category, that of values (not to be confused with the act of setting worth). To him, value is the standard by which employees set priority in their daily decisions. Corporate values play an important part in how employees work and think within the workplace. Christensen gives a classic example of this by looking at limits or boundaries set within the strategies of businesses. · ·
Values are defined by what a business CAN DO or is willing to do. Values are defined by what a business CAN’T DO or is unwilling to do.
For example, a company’s overhead requires it to achieve gross profit margins of 40%, then a value or decision rule will have evolved that encourages middle managers to kill ideas that promise gross margins below 40% (Christensen, 2000). Value is a matter of perspective. It is sometimes difficult placing value on intangible benefits. However, in order to reflect the true cost of doing business, intangible benefits need to be included. Intangibles such as improved customer service, improved productivity and reporting, and easier access to meter information are but a few benefits that are inherent in implementing AMR. Couple that with the benefits of data manipulation (forecasting, leak detection, usage, customer history) and the advantages soon outweigh the disadvantages associated with change. A utility manager needs to identify costs savings in all of these areas as a means of enhancing productivity and improving return on investment. Applying man-hours and material costs to determine the value of identified needs is a way of figuring costs associated with implementing an AMR system. Feasibility Study Some systems would provide more or less value over other systems due to features and functions or because of limitations imposed by budget considerations. A feasibility study answers the question as to whether the utility can afford the AMR system and whether the system meets the needs previously identified. It is designed to assess risks and validate assumptions associated with implementing new technology. The study should answer the concerns facing managers when implementing the AMR system and should provide a road map for implementation: · · ·
What the current infrastructure is and the limitations. What the projected AMR infrastructure will accomplish. What the transitional strategy between the current and projected will be.
All technological changes cause constraints on resources and should be evaluated and defined. Depending on how outdated or technology-poor an organization is will determine
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
the level of transition and learning needed for implementing AMR. feasibility, look at certain key issues as drivers of change: · · · ·
When evaluating
Open standards for compatibility, current and future. Knowledge base requirements such as technical expertise and knowledge of the technology. Experience, whether abundant or lacking, that allow for making technological change and sustainability of that technology. When evaluating sustainability, look at training and support requirements.
Sustainability is a critical element of the entire feasibility study. Open standards, knowledge base requirements, and level of experience contribute to an organization’s ability to implement and sustain technology. Things that contribute to poor implementation are: · · · ·
Complicated or sophisticated technology requiring technical or engineering expertise not found at the organization. Low level of technical knowledge or experience within an organization. Lack of understanding of the limitations of the technology being implemented. High expectations and misconceptions associated with the technology.
By identifying these things within the feasibility study, managers can affect a smooth transition between current and projected systems. A decision maker or utility manager needs to know his organization’s capabilities and resources. With that in mind, he needs to ask key questions about AMR and how it fits into constraints of his organization. · · · · ·
Will the AMR system fit into my current infrastructure or will it require changes? Will the AMR system work without additional purchases (software, hardware, or services)? Is the AMR system a proprietary system or an open protocol system? Do we have the necessary expertise for installing, operating, and maintaining the technology? Can we sustain the technology both politically and financially?
Lastly, evaluate the AMR system itself. This can be accomplished by initiating a trial over a set period. The trial should accomplish certain things: · · · ·
Test the practicality of the technology. Educate staff on processes and procedures. Delineate product functionality and limitations. Allow for comparison between like competing products.
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In most cases, a trial consists of inaccessible meters being outfitted with AMR. This will help evaluate the system in a hard-to-read environment and provides instant savings of costs associated with getting those reads. Cost Benefit Analysis The CBA is used when decisions are needed for planning or in support of a series of decisions when evaluating a certain program or proposal. The analysis summarizes for the decision makers the positive and negative impacts of any course of action being contemplated (Schmidt, 1999). The CBA helps justify expenditure associated with purchasing an AMR system. At a minimum, the analysis should provide a range of options or alternatives from which a decision can be made. In most cases, the options consist of comparing AMR to non-AMR alternatives. A cost benefit analysis consists of many components, depending on who is asked. At a minimum, it should contain the following: · · · · · ·
Needs of the utility Current system and impact of AMR changes Proposed AMR comparison Options not being considered and why Identify value(s) and benefits as costs (savings or loss) Assumptions or Expectations associated with Implementing AMR
The needs of the utilities are expressed in the need assessment and are given cost value in the feasibility study. The needs may be simple or complex depending on the hierarchy of the organization. The needs should be of sufficient scope as to justify changes incurred through implementing an AMR system. As part of the need of the organization, outline the current system requirements in a clear and concise manner, defining areas of improvement and the changes that the AMR project will cause. Current costs and proposed savings should be highlighted in this portion. When designing the proposed AMR comparison, identify the risks associated with each system and the benefits derived by implementing that particular AMR solution. Each risk and benefit normally can be assigned a value that makes decision making easier for management. The last portion, that of assumptions and expectations, covers those areas that affect the organization over the life cycle of the project. These include costs associated with human resources, and logistics and maintenance. Included in this is the “what if” aspect of risk assessment. Identify the financial impact an assumption may have on the project if it proves to be false. This process, called “sensitivity analysis,” covers assumptions about the values and trends analyzed.
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
Cost Benefit Analysis Case Study A township in the state of Michigan provided us with an example of a cost benefit analysis, which they used to determine their AMR decision. Their main emphasis in the analysis dealt with meter reader man-hours required to do the quarterly reads by two employees. The accounts totaled 25,225 customers with an annual total reads of 100,900 (4 quarters X number of customers). The accounts were further broken down into three major routes or bill areas as seen in Figure 3 of the chart. The rate of unscheduled reads due to inclement weather or other reasons stayed steady from 1999 to current year. The significance of unscheduled reads is that it pulls employees from tasks that were scheduled and required. This can be viewed as a negative impact on mission accomplishment and, therefore, an incurred negative cost.
Unscheduled Reads Extra employee hours per year
1998 136
1999 97.5
2000 *
2001 *
* Trend shows flat linear progression Scheduled Reads Total 2001 Man-hours = 1,735.59
Figure 2. Unscheduled and Scheduled Reads The charts in Figure 3 and 4 indicate a cost savings in man-hours associated with implementing AMR systems. The chart in Figure 4 breaks down the graphical representation of Figure 3 into numbers demonstrating the differences between AMR and manual reads when computing man-hours.
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
700.00 600.00 Hrs . A nnually to Collec t Data
500.00
Manual
A .M.R.
400.00 300.00 200.00 100.00 0.00 1
2
3
Bille d Custom e r Are a
Figure 3. Manual verses AMR Township Department of Public Works Manual Meter Reading Data Collection Analysis Annual Time Requirements
Billed Area I II III
Number of Accounts 8,115.00 8,132.00 8,978.00
# of Quarters
Manual Time Qrt. (Hrs )
4 4 4
Manual Time Annually (Hrs )
156.89 131.66 145.35
627.54 526.63 581.42
1,735.59
Total Est. Tim e Annually Dedicated to Reading Meters Manually (Hours):
Automatic Meter Reading (AMR) Comparative Analysis Annual Time Requirements Billed Area I II III
Number of Accounts 8,115.00 8,132.00 8,978.00
# of Quarters
Auto Time Qrt. (Hrs )
4 4 4
Auto Time Annually (Hrs )
6.45 6.46 7.13
Total Est. Tim e Annually Dedicated to Reading Meters if Fully Autom ated (Hours):
25.79 25.84 28.53
80.16
AMR Time Savings Ratio over Manual Data Collection: 21.65 to 1
Figure 4. Manual Verses AMR
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
It is interesting to note that the AMR data displayed in the charts is based on meter readers collecting the reads while driving the routes as opposed to walking the routes. In this study, the manual cost per read was $1.06 as opposed to AMR, which equated to $.02 per read. When figuring the manual and AMR cost per read, the township included meter reader salaries, benefits, car leases, gas and oil, insurance, and administrative costs. The benefits in savings amounted to over $105,000 annually. Meter Reading Cost Analysis: (Using Two Meter Readers to Manually Collect Data): Salary:
Benefits: Car Leases: Gas: Oil Insurance: Admin
$61,028.00 $29,893.88 $5,005.44 $194.00 $50.00 $1,838.00 $9,230.77
Provided via Payroll Dept. Provided via Payroll Dept. Car Leases $208.56 per month * Two Vehicles. Based on 4,000 Miles per Yr. 20 Miles per Gal. * $.97 per Gal. Via F&O Based on 2 Oil Changes @ $25.00 per Change. Est. $919.00 per Twp. Vehicle by MMRMA per F&HR Dept. W/S Fund Charged $300,000 for FY 2000 by Gen. Fund to provide Gen Services / 65 Full, Part & Summer Employees.
Total Annual Exp. Related to Reading:
$107,240.09
Number of Accounts Read Annually:
100,900.00
Cost per Manual Meter Read:
$1.06
Meter Reading Cost Analysis: (Using A.M.R. Technology and a Portion of One Employee's Time to Collect Data): Salary: Benefits: Car Lease: Gas: Oil Insurance: Admin:
$1,227.90 $601.47 $100.71 $57.47 $25.00 $36.98 $185.72
1 Emp. Salary / 1992 (Ann. Working Hrs.) * Est. Ann. Time for A.M.R. 1 Emp. Benefits / 1992 (Ann. Working Hrs.) * Est. Ann. Time for A.M.R. Ann. Lease Exp. 1 Car / 1992 (Ann. Working Hrs.) * Est. Ann. Time for A.M.R. 296 Twp. Miles / 20 M.P.G. * .97 per Gallon * 4 (# Times Ann. To Read A.M.R.) Est. 1 Oil Change Annually Approx. 1,184 Miles Annually to Read A.M.R. $919 Est. Ann. Fleet Coverage / 1992 (Ann. Work Hrs.) * Est. Ann. Time for A.M.R. $300,000 (Fee W/S Charged by Gen. Fund for Admin Support) / 65 Employees * 1992 (Ann. Working Hrs.) * Est. Time for A.M.R.
Total Annual Exp. Related to Reading:
$2,235.25
Number of Accounts Read Annually:
100,900.00
Cost per A.M.R. Meter Read:
$0.02
$105,004.84 Est. Annual Cost Savings using A.M.R. over Manual Data Acquisition.
Figure 5. Annual Costs Savings The cost benefit analysis provided by this township applied only the associated costs of reading each individual meter. Some of the benefits in Figure 1 were applied while other intangible benefits were not considered. For example, the hours that were once allocated to meter reading would constitute a cost benefit since they can now be used to eliminate backlogged maintenance or accomplish other tasks normally not considered due to personnel constraints. This increases organizational efficiency and capability.
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
invested that amount over a period. The Cash-Benefit Analysis for the Figure 5., statistics would be depicted as seen below in Figure 6.
Township Cost-Benefit Analysis 1
No. Years Warranty No. of Accounts (units)
10 25225
Cost Savings in Personnel $105,000.00 Annual Get Reads Cost $2,235.00
Cost Savings In Personnel
2
$105,000.00 $105,000.00
Annual Get Reads Cost
$2,235.00
Initial AMR Investment
$868,955.00 6
Initial AMR Investment
3
4
5
$105,000.00 $105,000.00 $105,000.00
$2,235.00
$2,235.00
7
8
$2,235.00
9
$2,235.00
10
$868,955.00 Cost Savings In Personnel Annual Get Reads Cost
$105,000.00 $105,000.00 $105,000.00 $2,235.00
$2,235.00
$2,235.00
$105,000.00 $105,000.00 $2,235.00
$2,235.00
Figure 6. Cost Benefit Analysis Work Sheet The formula for determining whether to go with the project or not is based on how great the benefits are over the costs within the life of the project. In other words, benefits divided by costs should be greater than one.
B / C = Present Worth of Benefit > 1 B / C = Annual Worth of Benefit > 1 Figure 7. Cost Benefit Formula In some instances, if the benefits equal the costs (or break even situation) then the project may be justifiable. In other instances, when the costs outweigh the benefits, the project may be justified as in the case of safety or human welfare. The final analysis would use the interest table for cash flow analysis (or a financial calculator) as depicted in Figure 8 where the resultant is less then one. The interest used was 5% or what a standard CD interest would be. Deciding which interest table to use will depend on how aggressive an organization would be in investing that same amount of cash.
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
Conventional B/C ratio Annualized Investment = $868,955 (A/P,5%, 10) = $868,955(0.12950) = $112,529.67
.91
B/C = Benefits/Costs = ($105,000)/($112,529.67 + $2,235.00) = P= $ at the time 0 A= $ at each period F= $ at a future tim e
(First Cost or Purchase Cost) (Operations & Maintenance, Overhead, Scrap, Direct Costs, Indirect Costs) (Disposal Costs, Salvage )
Figure 8. Final Analysis Formula While this particular project is borderline, it can be feasible to implement. Again that depends on the objectives and viewpoints of the decision makers. Additionally, the total savings and costs were not completely captured in this analysis. Intangible benefits can actually offset the results, making the number above one. Request For Proposal Once the studies have been made and the project for implementing AMR is approved, the normal procedure is to submit a Request For Proposal (RFP). The request lets bidders know that an organization is in need of a service. Note that a Request For Information (RFI) can precede an RFP and the steps outlined above. The request does not obligate any organization since it merely asks data to provide input to an RFP. It does, however, serve as a flag to bidders that there is an interest in their technology as a possible solution to specific needs. It is a good indicator that an RFP is in the making. The RFP should define needs by delineating requirements and criteria for awarding a contract. It should also allow for the trial periods – providing an opportunity for evaluating the products offered. The RFP includes specifications required of the equipment and performance measures it must pass in order to meet the needs of the utility. It would include, if the entire process is being subcontracted, the performance standards expected by the utility and any support conditions necessary to install, operate, and maintain the system. When receiving bid proposals from contractors, look at how they structure their response. Look critically at how they answer your needs: · ·
Do they provide solutions or mere product listings? Do they link features and functions of their product to specific needs addressed in the RFP?
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Assessing Automatic Meter Reading (AMR) Technology (Assessment Strategy)
· ·
Do they offer a relationship verses a sale? Do they provide evidence of timely delivery and budget adherence?
Tom Sant (2001), President of Sant Corporation and author of Persuasive Business Proposals, lists three points for evaluating proposals submitted in response to an RFP: · · ·
responsiveness – are we getting what we need? competence – can they really do it? value – is this the smartest way to spend our money?
Using these general guidelines would increase the utility manager’s ability to determine which responses are tailored to the utility’s needs. Conclusions Determining what type of technology to implement and how much to expend financially can be a difficult process. The key is to do the homework and plan for a successful implementation. By identifying key players early on and defining project parameters, by doing the need assessment, feasibility study and cost benefit analysis, the utility manager will have the tools for making the correct decision and strategy for the organization. Making decisions can be politically difficult. The need assessment should include those employees who have an invested interest in any change. The feasibility study and the cost benefit analysis would provide a basis for decisions based on facts and statistics and not personal choices. These things ensure that the best decision possible is made for the least amount of investment. References Anonymous (2001, January). Automatic Meter Reading (AMR) Feasibility Study and Cost Benefit Analysis Report (Unpublished township report used by permission.) Christensen, C.M. (2000, March-April). Meeting the Challenge of Disruptive Change. Harvard Business Review, Vol. 78, No. 2., p66. Cunningham, J. (2001, January) Internet Meter Reading and the Price of Cabbage. Utility Automation, Vol. 6, No. 1, p6. Fricker, David (2001). The Business Case: Preparing a Cost Benefit Analysis. (On-line) Available: http://members.ozemail.com.au/~dfricker/cba.htm. Sant, Tom (2001, July-August). How to Write Winning Proposals. Electric Perspectives, Vol. 26, No. 4, p30-37. Schlenger, Donald L. (2000, August). Best Meter Management Practices for Water Utilities. Water Engineering & Management, Vol. 147, No. 8, p14-15.
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Schmidt, Marty J. (1999). What’s a Business Case? and other Frequently Asked Questions (On-line) Available: www.solutionmatrix.com. Schmidt, Marty J. (1999). Business Case Essentials: A Guide to Structure and Content (Online) Available: www.solutionmatrix.com. Author: Bill Melendez RAMAR LLC P.O. Box 110127 Research Triangle Park, NC 27709 Tel.: (919) 991-9924 Fax: (919) 991-9946 E-Mail:
[email protected] Internet: www.ramartech.com
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Hydraulic Modeling with GIS, Integration or Import, What are the differences? by Richard N. Stalford, PE/RNS Consulting Abstract Integration of hydraulic model to Geographical Information Systems (GIS) has long been of interest to major utility centers everywhere. The main reason is associated with the maintenance of two or more dataset is time intensive and costly. By maintaining the main GIS and an additional hydraulic model dataset, twice the work and data entry would be involved. This paper will review the advantages and criteria necessary to properly coordinate a GIS program to prevent the double entry of information. Many independent software or modeling packages are available on the market and at least one very powerful free one, EPANET from Environmental Protection Agency. This paper will show that a feature rich environment for hydraulic modeling can still be maintained with only one dataset. Also reviewed will be the popular concept of IMPORTING data to hydraulic models and the issues associated with this approach. What are the advantages and disadvantages of these two main modeling and GIS approaches? You will have the tools to make educated and informed decisions on which approach is correct for your situation. This paper will concentrate the case study examples on water hydraulic modeling, but the same approach is valid for all other utility modeling and data storage. Keywords GIS, Geographic Information System, Utility Modeling, Utilities, Water System Analysis, Open Architecture systems Introduction There has been a long-standing desire to full integrate models with graphics system. The problems have always been which models and which graphic systems. First lets take a closer look at this desire before we get into the nut and bolts of how to accomplish it. Modelers of all kinds have struggled with the concept of simplifying model to make their tasks at hand not so arduous so as to make their goals so unattainable by the mere quagmire of data and paperwork. This paper will concentrate on utility modeling and how open architecture systems allow full freedom to handle data and see results in a variety of ways. By creating an open architecture and keeping open all the doors to different opportunities to view and analyze data, it gives a wider degree of input to properly operating utility companies. At this point is would be beneficial to review what a model is and which type of modeling we are reviewing. Models by nature can be, in this case, either analytical or graphical. The Geographic Information Systems (GIS) community refers to an intelligent mapping as a model and for them it is just that, a model with ability to perform advanced computations resulting in critical problem solving. For engineers, this may be a model, but the classical
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analytical model is of much more importance. While the graphical engine is used to display analytical modeling results, it is a tool not classically refer to as a model. Analytical models are advanced computation programs, which permit a wide range of “what if” trials, which permit a clearer understanding of what happens under plausible circumstances. For the purpose of this paper, a model will refer to an analytical computational definition, which allows engineers to simulate different operational conditions of a utility. I once had a client that wanted to use extended period simulation of a water distribution model to understand their water system better under maximum day demand periods. The goal was very attainable, but the model they were using resulted in a skeleton model of their system generating over 2000 printed computer pages, which then had to be reviewed. While this could have been done with an unlimited quantity of staff hours, the accuracy of dealing with so much data in this manual manor is somewhat questionable. The answer to their problem was easily solved by created an integrated graphics and modeling system, which allowed a significant quantity of data to be reviewed in an easy to handle graphics format, and then concentrating on critical issues resulting from the modeling. In this particular case, pressure was a key indicator of problem areas. Also pump operations running of the ends of their pump curves was another issue. Key issues could easily be reviewed if the output was digital and searchable. Lastly, it is very important to understand the concept of open architecture and also one persons open architecture is not another’s. It is very confusing if you look at the available shrink-wrapped software what they define as open architecture is not what will be used here as open architecture. Open architecture is when complete independent software packages can be tied together in a unified and structure way to allow data to flow from one to the other. Now there is the concept of IMPORTING which many software packages consider a part of their open architecture concept. In this paper IMPORTING will not be considered as part of the concept and in fact that is the major thrust of this paper, that in fact IMPORTING for modeling and graphical purposes of large dataset is not a desirable feature. This concept will be reviewed in detail in this paper. For the purpose of this paper, modeling will not only be considered to be of the analytical variety, but in specific water hydraulic modeling. This should not take away from the concept because modeling can be of any analytical variety. Wastewater, electric, gas, or any other utility modeling could be applied equally to this open architecture concept. It just so happens that most of my experience is with hydraulic modeling of water distribution system and applying them to GIS and open architecture systems. In the interest of fair play, this paper will not list the available commercially available software packages that say they have integrated open architecture system that hydraulically model water distribution system. We will on the other hand use a free software model as a very good example of modeling integration with graphics. This package, EPANET, is available free from the United States Environmental Protection Agency. It models both hydraulically and water quality water distribution (pipeline) system and is available on the Internet at http://www.epa.gov/ORD/NRMRL/wswrd/epanet.html.
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Open Architecture An open architecture is one where data can flow through predetermined paths between integrated modules. This sound easy and frankly it is not that hard to accomplish, but it can’t be accomplish with straightjacketed software that are available from software companies that say they can meet all your needs. The reason this can’t be accomplished truly from software companies is that they are writing software for the masses rather than particular situations and needs. Each project has its own set of requirements and data formats and generic software no mater how flexible they claim to be, have some shortcomings which have to gotten around. Custom software that addresses the specific needs of the project will truly satisfy the need for open architecture and particulars of the project. Figure 1 is an example of an open architecture where the data flows from the graphics to the models. This is an older model but the concept is the same. The models here are older hydraulic model, but the point can be made very simply that substitutions in this type of program is very easy. The models here read an ASCII file for input, which is created by the database application. The application can be changed at any time to meet the need of another model such as EPANET. I think the case can very easily be made that this is an open architecture system because the model can easily be changed. That cannot be said for shrinkwrapped software that completely addresses all the relevant goals of the project. Whatever model is used in the shrink-wrapped software is what you are stuck with, unless you wish to either by an upgrade, which is usually not available on your time schedule or needs or you must convert all the data from one system to another because a different model is desire.
Hydraulic Models
Geographic Information System
Reports
EXKYPIPE BNETQ
Database Application
SCADA Figure 1 – General example of Open Architecture
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So what is the main goal in an open architecture system is to be able to change one of the modules without the need to completely changing the complete system. Some adjustment is required by the database application to meet the needs and coordinate with a new module but the main system is still in tacked and is maintained. It is also important to notice that additional modules not originally considered in the project can be added as requirements change and needs expand. In Figure 1, a maintenance module is added at a later date to coordinate work orders and other information, which may be important to the model. Also SCADA (Supervisory Control and Data Acquisition) can be integrated which is a very powerful feature. Now tank fluctuations can be directly compared to the model result within the database application. This can be very useful in the calibration phase or later what if test. Cost of Custom Software Inevitably, everything comes down to cost and how to pay for projects. In this case, it is without question that custom software solutions are more expensive to implement on a single license system. BUT and there is a big but associated with these approach, almost every five years or so large utilities model their water and other system utilities. Growth demands that detailed analysis be reviewed to ensure that public water systems be able to stand up to the needs of expansion and continue economic growth. In the case of the open architecture approach, more sophisticated models are continuing to be developed and this is where this approach become very cost effective. If the model for water systems change every master plan then only the module needs to be exchanged and the database application adjusted, but the graphics which the model is based which has all the pipelines and the nodes network system can be used with a new model. This is a very powerful feature. Also if desired, two models could be linked to the system. If features from one are not adequate to meet the complete project goals, then two models could be based on the same graphics system. Importing IMPORTING as far as this paper is concerned is a tool to be used at the start of a project only to get all the data from one system and into another. If additional infrastructure is added as the system expands, this information should be added to the system in such a way as to be native to the graphics used and not IMPORTED. A good example of importing is the need to use data in more than one place. If a GIS is used to ensure and support other agency needs, like mapping, then data should be added to only one place one time to meet the complete needs of the system, mapping and modeling and whatever else is required. If live demand analysis is desired from the water meter billing system, then a live link should be made to allow the system to coordinate directly. We should not EXPORT from the meter billing system and then IMPORT to the modeling system unless that is no other way. And there usually are other ways. A good example of a bad data input process is to add pipeline graphic infrastructure to a graphics system then EXPORT and IMPORT into the model. This requires that two systems
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be maintained in order to keep the graphics mapping and model up to date. Here is where the economic really play a large part. Which is more economical, inputting the infrastructure to one system then EXPORTING and IMPORTING or just inputting to a system that meets all the mapping needs. Try doing the former approach over a five-year period and see how many staff hours are wasted. The aspect of EXPORTING and IMPORTING is that software is continually being updated. If the data entry program is updated than in the open architecture approach only one adjustment is necessary, but on a closed architecture or importing/exporting system, two possible upgrades could have double the negative effect. The only constant in the universe is change, and undoubtedly someone will think a feature needs adjustment or for that matter elimination and then you are stuck. A good example is the upgrade from AutoCAD Map Version 4.0 to Version 4.5. This upgrade made a significant change in manor and feature of making shapefiles. This feature changed to the point that the shapefiles that were required by the project could not be create any longer with the new features. Luckily, the older process still worked in the new version, but AutoDesk had to be consulted to figure this out. Support Information In an open architecture system there are many possible ways to analyze data and touch and coordinate with other systems. For major and/or repetitive analysis, a formal data pathway can be defined and setup, but for the on and off type of analysis that occur once in a while, there are several ways to get data out and analyze it. Most systems will allow the user to export data, but an open architecture system usually has the most leeway and latitude in allow this to occur. Software Development There is always the question of what development environment to program and are we going to get stuck using a software language that will tomorrow be obsolete. We always face the questions in terms of who owns the software, who maintain the application, and how much will upgrades cost. First, if you use any development language in the Microsoft Development Suite then you are standing on fairly solid ground. As much as I like options and not supporting a possible future monopoly, there is a lot to be said for using tools that are in general use that have a solid future. All of the applications that RNS Consulting has create for our clients are written in Visual FoxPro. Some would say, why not use Visual Basic, it has a larger following, larger market share, and more programmers are available to code applications. This is true, but Visual Basic does not lend itself to database manipulations as easily as Visual FoxPro does. Tool sets have to added to Visual Basic to get it to do the same things that Visual FoxPro does right out of the box. Once you add these other toolsets you are dealing with third party vendors and then what do you do when new versions and upgrades and you have conflicts between third party packages. You have a mess on your hands.
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RNS Consulting does not license software. We write software for clients and the code is mutually owned. Our clients are free to hire another programmer if they wish and usually find this refreshing attitude much easier and encouraging to actually return to us for additional work. This also allows our clients to install the application on as many machines as they wish. Look for this feature when dealing with contractors. Insist that the code be burned on a CD and a deliverable of the project. Also you may need to do a cost benefit analysis regarding cost of licenses and the number of license you will need. There are some circumstances that require even RNS Consulting to charge for separate machine installations, but these are due to purchased options that are used at the client’s insistence and are required by those software vendors that provide the option. ESRI’s Map Object is a prime example. A Map Object license is required for each machine it is installed on even though the object is used within the application we provided. Always arrange for continue support services to work out any anomalies which arise. You may upgrade a non-associated software package but it may have long ranging effects, which were not foreseen. Install certain version of Microsoft Data Component and you may inadvertently update the ODBC (Open Database Connectivity drivers), which may affect the application. Also there are always little feature changes you will want that need some vehicle of support that were not intended in the original contract for the system. There needs to be some leeway and flexibility for these changes. There is one last thing that needs to be stated. I don’t wish to make a large deal about it, and there will be many people that will not agree with this statement. But like any consultant, my interest is in giving you tools to make informed decisions to help in developing a strong toolset. Microsoft ACCESS is not a development tool; it is not available in the Microsoft Development Suite and for good reason, in is available in the Microsoft Office Suite. Microsoft ACCESS does not support a fully functional development environment. You will find a large group of people who feel that they can code anything in ACCESS and it is probably true, I can code almost anything is the original Basic language that was originally used in the DOS operating system. But talk to any fully qualified developer that has used any of the Microsoft Development Suite toolsets and they will probably agree with this statement. Don’t be fooled by the fact that software vendors are willing to code in ACCESS, they are meeting a market niche not a true development need. There are many other full feature tools that are available to use as a development environment. They can be very usable and we don’t wish to close the door for their usage. Be careful if you go outside the Microsoft Development family. You could build a very strong application or one that will have no development support in the future. Conclusions This paper basically has only once conclusion. Choose coordinating system carefully with a wide degree of latitude and flexibility for future use. As a conclusion to this paper, I will guarantee you that any system you use will be used for a long period of time and by more staff members of any organization if more thought is given to keeping more possibilities open than if settling for a short term solution that meets only the goals that are currently identifiable by close architecture systems. 420
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If you intend to purchase software in a shrink-wrapped package with the goal that only what comes in that box will meet all your needs then you have dug yourself a hole before you even have the opportunity to put the CD in the computer. Customized software is more expensive in the very short term, but has a very short payback period and over the life of the use of the data and the life of the organization, will serve you much better. In 15 years of watching software companies come and go with fluctuating markets, it never ceases to amaze me that people have not learned that short term thinking will not be easier in the long run. Why do you think those software companies did not last. Author: Richard N. Stalford, PE RNS Consulting, Inc. Tel: (704) 821-3842 Fax: (704) 821-3844 E-mail:
[email protected]
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FAST TRACK TO THE TOP - SUCCESSION PLANNING FOR THE CARIBBEAN by Ros Taylor, Plus Consulting, UK
Abstract Leaders and senior managers change jobs, move on or get promoted often leaving a void behind them. This paper looks at succession planning – how the young executive of today can be prepared to take on the senior roles of tomorrow. Fast Track to the Top is based on research conducted with 80 chief executives from Britain and the States which involved interviews and profiling to benchmark the skills that took them to their positions of power. The group included Sir Bob Reid of the Bank of Scotland, Charles Dunstone, Carphone Warehouse, Sir Richard Greenbury, Marks and Spencer and Dame Stella Rimington of MI5. The Ten Commandments for Success rated by this group provide the basis for this session with a particular focus on issues relating to the Caribbean. Introduction: Succession planning is important for any management team be they from the public or private sector. It is especially relevant for the Caribbean as they seek leaders from within their own communities rather than having to import them from outside. So if the Caribbean are going to grow their own leaders, how should that be carried out? What characteristics should be sought, can these be trained and if they can be, at what age should training take place? We decided to interview 80 business leaders to find out what made them tick. We analysed their skills, their attitudes, their backgrounds and their working habits to determine what helped them to reach the top. The results of our interviews are a true guide to the characteristics needed to reach the top of a department, company or profession. We then used the findings to assemble a practical programme so that young pretenders can be trained to take over the reins. We decided to ask questions of the directors themselves face to face. Of interest to us were their offices, the size, the décor, the art on their walls. Their secretaries were a fund of interesting information as they escorted us along corridors and into lifts. Their body language and often their replies spoke volumes as to whether the captain of industry we had just seen was a sweetheart to work for or a swine. We were able to make contact with a wide range of leading executives, far more than expected, and found them to be generally accessible and helpful. When they were not, we
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still attempted to talk to them to ensure that our results were not based on a self-selecting sample of ‘nice’ directors only. In general, we aimed at the top of the organisational tree and spoke to established chief executives, chairmen, managing directors and the like. While you may not aspire to these dizzy heights, the people at the top have mostly passed through the lower ranks of directorship and, we reasoned, are most likely to epitomise the qualities of the ideal director at any level. In embarking on our work, we were particularly assisted by Jim Hindhaugh, formerly of Cranfield Business School. Ten years ago Jim interviewed chief executives in a number of countries. Cranfield have generously given us access to their data and this has been invaluable in setting the parameters for our own investigations. At this point we would like to acknowledge another interesting influence when we were developing the interview. This is the work of Dr Susan Dellinger on ‘Psycho-Geometrics’. Dr Dellinger noted that, when people are asked to select a geometric shape (from a square, triangle, rectangle, circle or squiggle) which best describes them as an individual, their selection closely correlates with certain personality characteristics. While there is no suggestion that this is a comprehensive and analytical personality test, it met the important requirement of taking very little time to complete. It also happens to be intriguing and fun to do. Our interviewees were fascinated with the results. Only one executive thought it too stupid for words. Everyone else has if anything been rather amazed by the accuracy of the results and demanded copies to try out on their team and the family at home. You of course will have a chance to try the test and will have the opportunity to benchmark yourself against the great and the good. The last part of the interview comprised The Personal Profile Analysis by Thomas International. We thought it would be interesting to discover whether there is a cluster of personality characteristics that correlate highly with success. High dominance coupled with high influencing skills were found to be characteristic of this group. Fast Track to the Top is presented as the ‘Ten Commandments’ of business success. This is essentially a distillation of the findings that emerged most strongly and most consistently as the defining characteristics of the people we interviewed. Results Board directors are not a race apart. As we carried out our interviews we found ourselves in the company of bright, hardworking people, but not creatures from another planet. They had a variety of IQ’s, expertise, and backgrounds. In other words, directors are just like the rest of us – and their positions are up for grabs. Interpersonal skills are all-important. Our directors were nearly always charming, persuasive and eloquent. Where they had faced challenges or found they had to acquire new skills, these were mostly behavioural rather than ‘technical’ subjects like computing and finance. These technical areas are like Herzberg’s ‘hygiene factors’ – you have to have them, but more of 423
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them does not lead to more success and does not guarantee success in the absence of interpersonal skills. Energy is essential. We commonly found people working 80-100 hour weeks, with punishing schedules and little time for relaxation. They had a great drive for success, and a commitment to their businesses and their employees. To keep up the pace they needed to be aware of their health and to stay fit. Directors are resilient. They cope with stress well, often saying that their work is not actually stressful. They often use distancing strategies by calling work a game, by retreating to other interests when necessary, or by using their domestic life as a cut off from business pressures. They are also a very healthy group, with only 10% having had any significant illness. John Spence, one of this 10% is a remarkable example of a man who gradually became blind over the last few years. This disability did not deter him from becoming chief executive of TSB Scotland. Male executives need emotional stability to achieve business success, but women don’t. The majority of men claimed that when things went wrong at home, they could not concentrate at work. In some cases their current stability had been hard won as they were into their third marriage. Women were different. When women had trouble with relationships, they channelled their energies into work. In fact, one young female chief executive, Tanya Goodin, who had set up her own website company was worried that her recent marriage would make her so happy that she would lose her competitive edge. Senior people do not set goals. This surprising finding is against the trend of conventional management wisdom. However, the fact is that relatively few of our interviewees had followed a planned road to success based on clearly identified personal goals. Most were essentially clever opportunists able to seize the moment when it came their way. When asked the reasons for their success, by far the most common answer was ‘luck’. However they did set goals for the business just not for themselves! Top people are fun and interesting. Despite their punishing work schedule, our group had a wide range of interests which they actively pursued. From sailing to opera, rollerblading to egg cup collecting, successful people live life to the full. It is clear that part of what they bring to their business is breadth of vision developed from a wide range of experiences. Successful people love work. A real secret of success is undoubtedly loving the job. Our group made no sharp distinction between their working lives and their social lives and did not begrudge the intrusion of work into personal time. Charles Dunstone of Carphone Warehouse when asked how he coped with the pressures of work could not relate to the question. “I just love what I do. There is simply no pressure involved in that”. Self-confidence goes with the job. Some of our interviewees were born confident, for others it came with the job. While few were completely nerveless, virtually all rated their selfconfidence as ‘high’. This seems to be an essential requirement since all recognised the need
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to speak up for themselves, to argue effectively with senior colleagues and to be the focus of attention in a range of business situations. Patience and tolerance had to be learned. When asked what major skills had to be learned to execute their senior posts, overwhelmingly the two most common answers were ‘patience’ and ‘tolerance’. It seems that these characteristics are not the natural behaviour of those who succeed, but simply have to be learned to make progress in the corporate environment. It is understandable that these thrusting, energetic individuals might expect everyone around them to be the same and of course they are not. Claire McGrath, director at Pfizer, put it so succinctly when she said that she had to “stop being a razor blade”. In a nutshell, we did not discover a new species of human being. With the inside knowledge, which this book provides, and a little practice, most people can emulate the skills and approaches needed to make it to the board. The result is ‘The Ten Commandments of Success’ for the aspirant director. Of course, we could have made it nine commandments or eleven commandments. But the top ten actually serve very well to demonstrate the attributes which most strongly and repeatedly emerge as the definers of success. The Ten Commandments 1. Problem Solve Our number-one rated characteristic is the ability to solve problems in a crisis. Business success depends on being the person who stays constructive and creative when the going is tough. You need to see that there is always a way through, even when those around you have given up. 2. Deliver the Goods Successful people know what has to be done. And they need to achieve results. The key is the development of a results focus in which the end point is clearly understood and there is a sense of urgency in striving to get there. Once there, of course, new goals are set and the process begins again. 3. Want to Win Those at the top have a drive to become successful and see this as an objective in its own right. They enjoy winning for the sake of it and often think of business life as a game. Their secret is an understanding of the rules and a real desire to master them. 4. Relate Our survey of leaders shows that they prize the ability to work with a wide variety of people. Leaders have learned to stay close to their customers and their employees. They take time to
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relate to other people and are empathetic, communicative and supportive. They also handle difficult people skilfully and value a happy domestic life. 5. Trust the Team Success is not achieved in isolation. Our directors knew that they had neither the time nor the ability to do everything themselves, and were highly dependent on finding and keeping the right team. Finding business partners and then trusting them is a key business skill. 6. De-Stress Directors consistently give a high rating to their ability to cope with stress and recognise that managing stress is now a business essential. There are many approaches to stress management, but the key is awareness and proactivity. In this, as in other aspects of business, successful people take control. 7. Love Change When we asked our sample of leaders whether they liked change – most people don’t – they told us that not only did they love change but saw their ability to initiate change as crucial to their success. Embracing change, and recognising that it is now a necessary part of business life, is an essential. 8. Know Yourself We were consistently impressed with the responses when we asked our directors what they saw as their strengths and weaknesses. Without hesitation they listed their talents, and then their failings. Confident self-knowledge is the building block for progressing in business. 9. Strike a Deal Our final commandment relates to the ability to negotiate. Leaders need to achieve ‘win-win’ outcomes with partners and providers. They have the creativity to construct a proposition from which everyone will gain, the toughness not to relinquish more than they can afford, and the charisma to steer the encounter to a successful conclusion.
10. Be confident Some of the CEO's in our sample were born confident; for others it came with the job. While few were completely nerveless, virtually all rated their confidence as high. This seems to be an essential requirement since they need to speak up for themselves, to argue effectively with senior colleagues and to be the focus of attention in a range of business situations. Each executive in the sample was asked how they would develop young managers.
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It was rare to find any formal progression planning. However Rentokil, The Marsh Group and Reckitt and Coleman do have structured programmes for the younger executive. Some admitted to having nothing, for example Eurotunnel and The Nationwide Building Society and certainly saw it as a need. Some answers revolved around broadening experience. Channel 5 has secondments with shareholder companies and Astra Zeneca sends young managers on oversees service. Marks and Spencer has a series of key note addresses for their high fliers. Some mentioned mentoring and coaching but very few. ‘Throwing in at the deep end’ featured widely with the caveat of lots of appraisals. When asked what were the key areas to develop in young managers, increasing selfconfidence was mentioned most often. Some executives felt that there were differences between the sexes and it was young women who required an increase in confidence whereas young men needed to know that promotion did not come as a right. Responses also clustered around seeing the bigger business picture, becoming aware of business development and looking at strategic issues. For the most part though, people skills and learning how to motivate and manage others were the main areas senior executives would like to see developed. As David Mitchell of Mitchell Associates in New York said ‘ young people are often great technicians but they need humanising’. A programme based on the Ten Commandments is available for training young people so that leaders can be grown internally to countries in the Caribbean Author: Ros Taylor Plus Consulting UK E-mail:
[email protected]
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UV Inactivation of Microorganisms in Water – A Review by Thomas M. Hargy and Jennifer L. Clancy, Ph.D. Clancy Environmental Consultants, Inc. Abstract Though long recognized as an effective disinfectant of many microorganisms, ultraviolet light has taken a secondary role in this application in the drinking water industry, where the use of chemical disinfectants has been favored. Recent concerns over the safety of chemical use, the health effects of byproducts of chemical disinfectants, as well as their relative ineffectiveness against Cryptosporidium, have caused treatment professionals to look for other means of water disinfection. Until recently, the issue of efficacy vs. Cryptosporidium would also seem to rule out the use ultraviolet light, as past research seemed to indicate the technology had little effect. However, recent studies, using more exacting methodologies, have demonstrated the profound effect which the physical disinfectant has on protozoan pathogens including Giardia and Cryptosporidium. Key words: Ultraviolet light, disinfection, Giardia, Cryptosporidium Introduction Cryptosporidium parvum is a pathogen of concern in water supplies. This parasite causes cryptosporidiosis, a disease causing profuse, watery diarrhea, abdominal cramps, nausea, vomiting and low-grade fever. In most well nourished, immunocompetent individuals, infection may last between 2 and twelve days, and is usually self-limiting. However, in patients with congenital or acquired immune deficiencies or in malnourished individuals, infection can be considerably prolonged, resulting in malabsorption, severe dehydration, and death. The need for removal or inactivation of this and other drinking water pathogens, with minimal reliance on chemicals, has recently brought a new focus on ultraviolet light (UV) and its effect on microorganisms. UV: a Physical Disinfectant UV refers specifically to light in the 40-400 nm wavelength region. Germicidal UV is that portion in the 200-300 nm range, and the most effective disinfecting UV is that at 260 nm, which corresponds to the peak absorption of DNA. As photons of UV are absorbed by DNA, photoproducts are formed which interrupt the ability of the DNA to replicate itself. This effectively prevents infection of a host animal by the microorganism. The amount of UV irradiation reaching a surface is expressed as milliwatts per square centimeter (mW/cm2). The UV dose is a function of irradiation times exposure duration, or mWsec/cm2. This is equivalent to millijoules per square centimeter (mJ/cm2).
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UV is widely used in wastewater treatment, and is slowly increasing in drinking water systems. It was first used in drinking water in France in 1910, and it was first applied in the United States in 1916. (USEPA, 1996). Types of UV Lamps The majority of commercial UV sources are mercury vapor lamps. Low pressure (LP) lamps produce nearly monochromatic light with a peak output at 254 nm, which very closely corresponds to the peak wavelength of DNA absorption. Therefore, these lamps are very germicidally efficient. The output of a second type of lamp, the medium pressure (MP) mercury lamp, is spread throughout the 200 to 300 nm range. While these are less efficient, they are much more powerful LP lamps, so significant bactericidal effects can be achieved with fewer units. A third type of lamp which produces UV is the xenon based pulsed lamp. While a major portion of pulsed lamp output is in wavelengths other than the bactericidal range, including visible (white) light, these also produce remarkable amounts of disinfectant UV. Advantages and Disadvantages of UV One of the major advantages of UV is that no chemicals are required to achieve significant disinfection of microorganisms. Of great significance in view of the Disinfectants and Disinfectants By-Products Rule is the reduction or elimination of any disinfection by-products (DBPs) of chemical treatment. Studies have shown there are no DBPs from the use of UV in drinking water (Malley et al 1996). Another advantage of UV is the minimal space requirements of a UV reactor. As UV lamp assemblies can be built into piping configurations, and because long residence-time contact chambers are not necessary, structural facility requirements may be minimized. A significant disadvantage to UV is that no residual disinfectant remains following treatment for distribution system protection. This lack of residual also makes dose measurement difficult. UV’s Effect on Microorganisms in Water The process by which the absorption of UV by DNA causes inactivation of organisms involves the creation of photoproducts which interfere with an organism’s replication mechanism. The significant photoproducts in UV disinfection are thymine dimers. These are created when certain bonds in the DNA strand are broken and new ones are formed, resulting in inhibition of replication. When microorganisms are incapable of replication, they are also unable to infect a host organism. Different organisms exhibit differing sensitivities, so that one species exposed to a given dose of UV will be inactivated by orders of magnitude more or less than another species exposed to the same dose. Generalizations can be made regarding the sensitivities of various types of organisms: Bacterial cells are quite vulnerable to UV; while most species may be inactivated by as many as 4 log10 with as little as 3 to 10 mJ/cm2, particularly resistant species may require up to 34 mJ/cm2 for that same inactivation. Some bacteria, such as Bacillus subtilis, endure harsh
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conditions by producing environmentally resistant spores. These bacterial spores may be quite resilient to UV irradiation, requiring 60 mJ/cm2 for 4 log10 inactivation. Viruses exhibit significant resistance to UV disinfection, relative to bacterial cells. Many, such as poliovirus Type 1 and Hepatitis Type A, will be inactivated by 4 log10 with 7 to 30 mJ/cm2. Others, such as rotavirus strain WA and the coliphage MS2, require 50 to 80 mJ/cm2 for that same level of inactivation (Chang et al, 1985, Wilson, et al, 1992, Battigelli et al. 1993). Finally, one of the most UV resistant organisms of public health concern to be identified is adenovirus. Present assay methods have shown adenovirus to require 120-140 mJ/cm2 for 4 log10 inactivation (Meng and Gerba, 1996). Protozoan cysts and oocysts pose a special concern to the water treatment industry due to the significant adverse health effects of Giardia and Cryptosporidium, their ability to pass through conventional treatment systems, and their resistance to chemical disinfectants, a characteristic especially pronounced by the latter pathogen. The efficacy of UV for the inactivation of Cryptosporidium has long been doubted by the microbiological and water treatment communities. This in large part has been fostered by the greater resistance of Cryptosporidium oocysts to chemical disinfection when compared to other microorganisms. The notion has been strongly reinforced, however, by inadequacies of the assays used to assess oocyst viability following UV treatment. Studies conducted in the mid to late 1990s using in vitro surrogate viability techniques indicated that relatively high UV doses are required for oocyst inactivation: UV/Cryptosporidium studies using in vitro surrogate methodology reference Ransome, et al, 1995 Campbell, et al, 1995 Clancy, et al, 1998
lamp type
dose (mJ/cm2)
LP LP LP
120 8700 180
log10 inactivation 2 >2 <1
During this time period, several researchers examined the actual infectivity of oocysts following UV irradiation, but only following high doses: UV/Cryptosporidium studies using infectivity methodology reference
lamp type
Dunn, et al, 1995 Clancy, et al, 1998
pulsed LP
dose (mJ/cm2) 1000 4380
log10 inactivation >6 >4
Finally, an exhaustive comparison of the in vitro surrogate methods against the more definitive animal infectivity techniques was carried out, and showed that the surrogates are not sensitive to low doses of UV (Bukhari et al, 1998). As a result, inactivation is underestimated by these surrogate methods. A review of more recent bench scale studies using cell or animal infectivity to assay UV efficacy identifies UV’s ability to achieve high log inactivation of Cryptosporidium at low doses.
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More recent UV/Cryptosporidium studies using infectivity methodology reference
lamp type
Bukhari, et al, 1998 Finch & Belosevic, 1999 Clancy, et al 2000 Clancy, et al 2000 Shin, et al, 2000
pulsed MP MP LP LP
dose (mJ/cm2) 40 10 3 3 3
log10 inactivation >3 3.2 3.4 3.0 >3
These results indicate that the UV dose response of Cryptosporidium oocysts is actually similar to that of bacterial cells, rather than being more resistant than viruses, as was previously thought. Giardia: While the above studies were primarily concerned with Cryptosporidium, two of these also examined the effect of UV on Giardia. Finch and Belosevic (1999) reported the response of Giardia muris to UV to be similar to that of Cryptosporidium. An evaluation of the dose response of Giardia lamblia found this human pathogen to be quite vulnerable to UV, exhibiting greater than 4 log inactivation at 2 mJ/cm2 (Shin et al, 2000). Pilot Demonstration Studies of UV vs. Cryptosporidium With the understanding that appropriate methodologies could quantify the significant effect of UV on protozoa, studies were designed to assess the ability of UV to inactivate Cryptosporidium in flowing pilot systems. A summary of these demonstration tests is provided here: Flowing system evaluations of UV inactivation of Cryptosporidium reference Bukhari, et al, 1999 Hargy et al, 2000 Drescher, et al, 2000 Mackey, et al, 2000 Klevens, 2001 Klevens, 2001
lamp type MP MP LP LP LP MP
system flow (gpm) 215 40 4 200 75 150
dose (mJ/cm2) 19 10 120 45 50 50
log10 inactivation 3.9 >4.4 >5.7 >4.7 >5.7 >5.7
These pilot studies were conducted on finished drinking waters, with one exception. In all cases, significant inactivation of Cryptosporidium was achieved. The study by Hargy et al, 2000 used recreational water from a Florida water park, following 3 days of heavy use. Oocysts which were added to this water and allowed to combine with its constituents were still inactivated by greater than 4 log10 by UV doses as low as 10 mJ/cm2.
431
UV Inactivation of Microorganisms in Water – A Review
Conclusions Balancing the need to provide effective microbial disinfection of drinking water while diminishing dependence on chemical disinfectants has been a difficult dilemma for the water treatment industry. Ultraviolet light has long been recognized as an effective disinfectant of bacteria and viruses, but not for protozoan pathogens. The present understanding of this physical disinfectant’s capabilities against these chemically resistant organisms opens the door for increased application of this technology in drinking water treatment processes. References Battigelli, D. et al (1993) The Inactivation of Hepatitis A Virus and Other Model Viruses by UV Irradiation. Water Science Technology. 27(3-4):339-342. Bukhari, Z., et al (1998) Proceedings, AWWA Water Quality Technology Conference, San Diego, CA. Bukhari, Z., et al (1999) Medium-pressure UV light for oocyst inactivation. J. American Water Works Assoc. 91(3):86-94. Campbell, A.T., et al (1995) Inactivation of oocysts of Cryptosporidium parvum by ultraviolet irradiation. Water Res. 29 (11) 2583-2586. Chang, J.C.H., et al (1985) UV inactivation of pathogenic and indicator microorganisms. Appl. and Environ. Microbiol. 49(6):1361-1365. Clancy, J.L., et al (1998) UV Light Inactivation of Cryptosporidium oocysts. J. American Water Works Assoc. 90(9):92-102. Clancy, J.L. (1999) Ultraviolet Light – A Solution to the Cryptosporidium Threat? UV News 1(1):18-22, International UV Association Clancy, J.L., et al (2000) Using UV to inactivate Cryptosporidium. J. American Water Works Assoc. 92(9):97-104. Drescher, A. et al (2000) Cryptosporidium Inactivation By Low Pressure UV In A Water Disinfection Device. Proceedings of the Small Drinking Water and Wastewater Systems Conference, Phoenix, AZ. Dunn, J., et al (1995) Pulsed light treatment of food and packaging. Food Technology, 49, 95. Finch, G.R., et al (1997) Effect of Various Disinfection Methods on the Inactivation of Cryptosporidium. AWWA Research Foundation and American Water Works Association. Finch, G.R. and M. Belosevic (1999) Inactivation of Cryptosporidium parvum and Giardia muris with Medium Pressure Ultraviolet Radiation. Proceedings, USEPA Workshop on UV Disinfection of Drinking Water, Arlington, VA.
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UV Inactivation of Microorganisms in Water – A Review
Hargy, T.M., et al (2000) Shedding UV Light on the Cryptosporidium Threat. Journal of Environmental Health, July/August 2000, 19-22. Klevens, C. (2001) Parameters for UV Disinfection of Surface Water. International UV Association Poster Session. Washington, DC.
Proceedings
Mackey, et al (2001) Comparing Cryptosporidium and MS-2 Bioassays: Implications for UV Reactor Validation. J. American Water Works Assoc. (in press). Malley, J.P., et al (1996) Evaluation of the By-Products Produced by the Treatment of Groundwaters with Ultraviolet Radiation (UV) and Post Disinfection Following Irradiation. Denver, CO: AWWA and AWWARF. Meng, Q.S. and C.P. Gerba (1996) Comparative inactivation of enteric adenovirus, poliovirus and coliphages by ultraviolet irradiation. Wat. Res. Vol.30 No. 11 pp. 2665-2668 Ransome, M.E., et al (1993) Effect of disinfectants on the viability of Cryptosporidium parvum oocysts. Water Supply, 11,75. Shin, et al (2000) Comparative Inactivation of Cryptosporidium parvum oocysts and coliphage MS2 by Monochromatic UV Radiation. Proceedings, Disinfection 2000: Disinfection of Wastes in the New Millennium. New Orleans, LA. USEPA (1996) Ultraviolet Light Disinfection Technology In Drinking Water Application - An Overview. Office of Water., EPA 811-R-96-002. Wilson, B.R, et al (1992) Coliphage MS-2 as a UV Water Disinfection Efficacy Test Surrogate for Bacterial and Viral Pathogens. Proceedings, AWWA Water Quality Technology Conference. Toronto, Ontario. 219-235. Authors: Thomas M. Hargy and Jennifer L. Clancy, Ph.D. Clancy Environmental Consultants, Inc. P.O. Box 314 St. Albans, VT 05478 USA Tel: (802) 527-2460 Fax: (802) 524-3909 email:
[email protected] [email protected]
433
Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions by D. S. McCorquodale, Jr., Spectrum Laboratories, Inc. Abstract Traditional water quality indicators such as E. coli and enterococci may be unreliable in marine environments. E. coli and enterococci are capable of re-growth in soils of tropical and subtropical regions causing elevated levels in the water column from land run-off. Bacterial indicators also have reduced survival in marine waters compared to viruses, such as coliphage. Coliphage, a virus that infects E. coli, can be used as a conservative tracer of pollution because they only proliferate in the presence of susceptible host bacteria. Coliphage enumeration has proven to be useful for the detection of recent fecal contamination. Developments of molecular biology techniques have allowed water quality microbiologists to assess the hygienic quality of water by detecting microorganisms that are difficult to culture. Studies have evaluated the use of a method for Bacteroides fragilis group (BFG), a group of bacteria present in high numbers in the feces of humans. Researchers at the University of Hawaii and several European researchers have proposed the use of C. perfringens as a microbial indicator of water quality. Analytical techniques are referenced for fecal coliform, enterococci, coliphage, Clostridium and Bacteroides. Studies in Biscayne Bay, Miami-Dade County, Florida show coliphage as a superior indicator as compared with fecal coliform and coprostanol. Analyses in Bell Channel Bay, Freeport, Bahamas used coliphage and fecal coliform to monitor a contamination event. Coliphage were detectable longer than fecal coliform. A combination of indicators (fecal coliform, enterococci and coliphage) was used to determine the source and extent of fecal pollution. Regrowth of bacterial indicators was indicated. The use of multiple microbial indicators in the Las Olas Isles in Broward County, Florida showed the need for multiple indicators. Detection of point source pollution was most successful when mutiple indicators were abundant with and surrounded by additional coliphage hot spots. The data suggests that various indicators are sensitive to different types of contamination, therefore it is important to select the indicator(s) best suited for a given situation. This paper is designed to describe these new indicators and methodologies and how they can be used by water managers to evaluate water quality Key Words: coliform enterococci coliphage bacteroides clostridium indicator
434
Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Waterborne enteric illness remains a major source of worldwide human morbidity and mortality. It has been estimated that one-half of the world’s population has suffered from diseases caused by polluted water, and over 10 million die annually from these diseases (McFeters and Singh, 1991). Not only is this seen in developing nations, but an increasing trend in waterborne illnesses has also been reported in industrialized nations. In the Florida Keys, microbial pathogens in sewage include Salmonella and Shigella spp., Vibrio cholera, enterotoxigenic Escherichia coli, and over 100 different types of pathogenic viruses. Fifty percent of all waterborne diseases are attributed to contaminated groundwater. Outbreaks of hepatitis, gastroenteritis, and Norwalk virus dysentery have been attributed to groundwater contamination from septic tanks (Paul et al., 1995). Well over 140 different virus types excreted in human feces and urine find their way into sewage and become water pollutants including enteric viruses that are pathogens of humans. Many enteric viruses can initiate an infection in humans even if present in low numbers. An infected person can shed up to 1010 infectious virus particles per gram of feces (Ricca and Cooney, 1998). Potential exposure to pathogens from contact with contaminated beach sand is being evaluated by the U.S.E.P.A.. It is impossible to attempt to identify all enteric pathogens present in a water sample. An indicator organism that is always present in fecal material and is readily identified is needed. There are three requirements necessary for a reliable indicator. First it should be native to the intestinal tracts of man and enter the water with fecal discharge. While relatively harmless, themselves, it is found in the company of other enteric pathogens. Secondly, it should normally survive longer than its disease-producing companions. Thus, once they have diedoff, the danger is normally past. Thirdly it should be relatively easy to isolate and identify because of specific biochemical or culturable reactions. Traditionally, total coliform bacteria are used as an indicator of fecal pollution. This group includes the aerobic and facultative anaerobic, gram-negative, nonspore-forming, rod shaped bacteria that ferment lactose in 24 hr at 35 C. The group include the genera: Escherichia, Citrobacter, Enterobacter and Klebsiella. It has been demonstrated that the feces of coldblooded animals contain certain bacteria that are in the coliform group. Soil run-off contains non-fecal bacteria that are also part of the coliform group. A sub-group of the total coliforms termed “fecal coliforms” grow mainly in the intestines of warm-blooded animals including man. These are predominately E coli and E. coli varieties. Since the coliform group exhibit rapid die-off in marine waters, their use as indicators of the presence of feces-derived pathogenic bacteria and viruses that can make them untrustworthy indicators in a variety of situations. Once an enteric pathogen of human origin enters a marine or estuarine environment, there are various factors affecting its survival. These include sedimentation, predation, parasitism, inactivation by sunlight, temperature, osmotic pressure, and toxic chemicals (McCorquodale and Burney, 1996). In addition, sampling and handling procedures before enumeration can affect the viability of injured bacteria. All of these factors can contribute to low false estimates of their numbers. Injured coliforms may comprise 90% or more of certain populations. Die-off of Escherichia coli is particularly evident in seawater in which, after an initial lag, up to 90% mortality may be observed in 3 to 5 days (Pettibone and Cooney, 1986). In addition, it has been shown that some fecal coliforms persist and even grow in certain environments. E. coli are capable of re-growth in soils of tropical regions causing elevated levels in the water column from land run-off.
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Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Therefore, the reliability of these particular indicators in marine waters is very conditional. At the moment coliforms and fecal coliforms stand as the universal indicators, despite their clear drawbacks (Armon and Kott, 1995). Clearly, a more source specific indicator is needed (Kreader, 1995). Fecal streptococci are another traditional indicator used to detect fecal contamination. Since fecal streptococci are more abundant in nonhumans than humans, fecal coliform to fecal streptococcus ratios have been used to distinguish between human and nonhuman feces (Kreader, 1995). However, fecal streptococci has been shown repeatedly to be very limited in marine tropical waters as an indicator, especially in the presence of recent contamination, due to their lack of numbers as a result of degradation. Their decrease can be explained by the rapid inactivation of the fecal streptococci species with low survival rate outside of animal intestines (Borrego et al., 1990). The use of the ratio of fecal coliform to fecal streptococci to predict sources of pollution is suspect in all waters and storm drains (McCorquodale and Burney, 1996). In addition, it has been shown that some fecal coliforms and fecal streptococci can persist and even grow in certain environments, and free-living coliforms may be indigenous to some tropical waters. Enterococci, a subgroup of fecal streptococci, have been promoted by the USEPA as a better indicator of heath risks in marine waters (Griffin et al., 1999). Coliphage/bacteriophages have been getting a great deal of attention for their effectiveness as indicators of enteric viruses in fecal pollution. Most studies seem to agree that these phages have surpassed the traditional coliforms as indicators due to their survivability in seawater, their inability to reproduce outside their host, and their similarity to human viruses. Because they are viruses, coliphage also exhibit a high resistance to water purification processes (Borrego et al., 1990), such as disinfections and other environmental stresses which coliforms are very sensitive to. Bacteriophages are also abundant in wastewater and, as such, were proposed as an appropriate fecal pollution model organism (Armon and Kott, 1995). Also, the quantitative phage assays are cheap, easy and rapid (Borrego et al., 1990). These advantages are due to the fact that coliphages are a type of bacteriophage, which are actually viruses that infect and replicate in bacteria, namely the E.coli bacteria. The somatic coliphage, which are the most common, initiate their infectious process by adsorbing to surface receptors on the bacteria. In contrast, the less common F male-specific bacteriophage is attached to the sex pilus coded by the F gene on the chromosome or plasmid. The F phages cannot be considered fecal indicators in the conventional sense since they are not consistently present at high levels in human fecal wastes. However, they are consistently and abundantly present in sewage and sewage polluted waters. The presence of these phages in a water sample could be used as an index of sewage contamination, making them a valuable tool for the assessment of water quality (DeBartolomeis and Cabelli, 1991). The somatic coliphage seem to be found more consistently in human fecal wastes, thereby making them more advantageous for other cases of fecal contamination that may not be necessarily related to sewage related problems. Several researchers have proposed the use of Clostridium perfringens as a microbial indicator of water quality (Fujioka, 1997). In Hawaii, the value of less than 50 colony forming units per one hundred milliliters (cfu/100ml) has been suggested as the recommended number for freshwater, and less than or equal to 5 cfu/100ml for shoreline waters. C. perfringens are common bacteria in human and animal feces. 436
Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Bacteroides spp. is another kind of bacteria that is used to evaluate fecal pollution. Bacteriodes spp. are obligate anaerobes that dominate the human fecal flora, and because some species may live only in the human intestine, these bacteria might be useful to distinguish human from nonhuman sources of fecal pollution (Kreader, 1995). The most abundant Bacteroides spp. in human feces has been detected only at low levels or not at all in feces from other animals (Kreader, 1995). Because they are obligate anaerobes, Bacteroides spp. does not survive in oxygenated waters, meaning they do not persist on their own giving false readings. The need to maintain anaerobic conditions during growth, isolation, and biochemical identification has discouraged their use as an indicator. However, detection methods that use DNA probes make it possible to discard the need to culture organisms in order to obtain detectable limits of DNA. By using polymerase chain reaction (PCR), specific DNA sequences can be amplified in vitro from a few copies to approximately a million copies in just a few hours. Furthermore, since each species has a unique DNA sequence, choice of the correct probe sequence and use of sufficiently stringent assay conditions can make DNA sequence-based detection very selective. The use of PCR detection of Bacteroides species to identify human sources of fecal pollution has several advantages over other tests for fecal pollution. The results of the survey indicate that the Bacteroides probes would be more useful than fecal coliform assays to distinguish sewage from farm runoff (Kreader, 1995). Molecular approaches have become popular and efficient methods for characterizing and tracking changes in the community structures of microbial populations (Bernhard and Field, 2000). Not only are molecular tests used for anaerobes such as Bacteroides, but PCR can be used to detect coliphage as well. Specifically, RT (reverse transcriptase)-PCR has been used for the detection and/or differentiation of enteric viruses in freshwater, marine waters, and shellfish (Rose et.al, 1997). New and improved methods in molecular testing will certainly improve the accuracy of quantifying indicator species. Combinations of indicators seem to be the most effective means to evaluate and qualitate fecal contamination on both a large and small scale. Simultaneous monitoring of water samples for alternate indicators, F-specific RNA coliphage, enterococci, and Clostridium perfringens, as well as direct pathogen monitoring for enteroviruses and enteric protozoa (Cryptosporidium and Giardia spp.) enables better assessment of fecal contamination and public health risks (Griffin et al., 1999). Other combinations have been found to be useful as well, some depending on the specific site that is tested. Microbial Indicator Methods Fecal coliform. Standard Methods 9222D - Fecal coliform membrane filter procedure uses an enriched lactose medium and incubation temperature of 44.5 +/- 0.2 C for detection of coliforms from warm-blooded animals and those from other environmental sources. Enterococci. EPA Method 1600 – Enterococci membrane filter procedure provides a direct count of bacteria based on the development of colonies on the surface of the membrane filter. A selective medium, mEI agar, incubated for 24 h at 41 C develops enterococci colonies with blue halo.
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Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Coliphage. Standard Methods 9211D – A five-milliliter water sample is mixed with five milliliters of tryptic soy agar and one milliliter of the host E. coli C culture. The mixture is poured into a petri dish and incubated. If the coliphage are present, the resultant infection of the host E. coli allows the virus to replicate and the viral particles burst out of the cell and infect adjacent host cells. The infection results in the formation of visible clear areas within the lawn called plaques. These plaques are counted and reported as plaque forming units per 100 milliliter of sample. Clostridium perfringens. EPA/600/R-95/030. The enumeration of Clostridium perfringens spores is achieved by using a membrane filtration technique as specified by the USEPA in 1995. Volumes of 10 ml and 30 ml are filtered and both used for calculation of the concentration. The purpose of two sample volumes is to overcome both low concentration and excessive turbidity. Colonies are usually well defined with little interference. Bacteroides fragilis group (BFG). Species belonging to the Bacteroides fragilis group (BFG) are analyzed using the polymerase chain reaction (PCR). Serial dilutions of the water sample are passed through a 0.45 um filter to trap the bacteria. The DNA in the sample is isolated and purified using a protocol from Ausubel, et al. (1990). The BFG-specific DNA is amplified and detected in each dilution. The highest dilution that resulted positive for BFG is used to estimate the concentration. Case Studies Biscayne Bay, Miami-Dade County, Florida. A comparison of fecal coliform bacteria and coliphage virus levels was conducted in fresh, brackish and saltwater. In fresh water (<10 ppt) the relation between fecal coliform and coliphage gave a correlation coefficient of 0.91 and at saltwater locations the correlation coefficient was 0.45. Coliphage proved to be a logical choice for a fecal indicator in marine waters since their titers are closely related to fecal coliform in freshwater, survive much better than coliforms in seawater, and can be enumerated by a simple method which is not subject to salinity artifacts Coliphage titers greater than 10,000 pfu/100 ml were detected in one northern Biscayne Bay station eleven days after a reported raw sewage discharge into a tributary creek, while total and fecal coliforms indicated no violation of water quality standards. Analysis of samples taken shortly after the discharge by the Dade County Health Department in the fresh water creek where the spill occurred, detected total coliform counts exceeding 24,000 cfu/100 ml. Comparison of coliform, coliphage and coprostanol (a highly labile component of mammalian feces) levels in the Miami River, Little River and Haulover Inlet were made. All three parameters showed severe sewage contamination at seven stations along the rivers. An additional five stations showed high sediment coprostanol levels and high coliphage titers, but were within state water quality standards for coliforms. An additional nine stations had elevated levels of coliphage without elevated coprostanol or coliforms. These stations were all associated with obvious sources of fecal pollution such as live aboard boats, marinas and surface runoff. Spectrum Laboratories, Inc. conducted analyses under contract with the Department of Environmental Resource Management, Dade County, Florida.
438
Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Bell Channel Bay, Freeport, Bahamas. This bay consists of five interconnecting sections. This study was conducted in the central section that is surrounded by private homes, a sport diving club, and resort condominiums. There were complaints of dirty water, bad odors, algal blooms, and fish kills. Coliform analyses of bay water conducted by the Bahamian Health Service showed no violation of water quality standards. The Grand Bahama Development Company contracted Spectrum Laboratories, Inc. to evaluate the problem. A package sewage treatment plant was located adjacent to the south bank of the bay. The sewer plant was designed for aerobic treatment and deep well discharge, but was later found to be discharging directly into the bay. Initial sampling revealed high levels of coliform bacteria (>1000 cfu/100 ml) and coliphage (>100 pfu/100 ml) adjacent to the sewage treatment plant. Coliphage was detected throughout the bay system. An illegal discharge pipe was located in the area of the highest fecal indicator counts. A steady flow of sewage was observed and sampled. The sample was partially diluted with bay water and had a five day biochemical oxygen demand of 69 mg/l and a total suspended solids of 75 mg/l. The sewer plant was taken over by the development company, quickly renovated and the effluent was chlorinated. After seven days of chlorination, the coliform levels were below 1000 cfu/100 ml, however the coliphage were still detectable at high levels throughout the bay. On day 7, all effluent was diverted from the bay to the redeveloped deep well. Ten days later, coliforms were undetectable in the bay, however, coliphage were still easily measurable. This is indicative of the potential survival of enteric viral pathogens well after coliform standards have been met, even in the case of well-chlorinated effluents. The level of fecal contamination in Bell Channel Bay rapidly depurated within about three weeks after upgrading of the sewer plant and the cessation of effluent discharge into the bay. Landfill, Broward County, Florida. The purpose of this study was to determine the extent of fecal pollution at a sanitary landfill where landscape trash and clean building materials are dumped. The local county environmental quality board found elevated coliform levels in the brackish water canals on the site. Spectrum Laboratories, Inc. used a series of microbial indicators and determine the potential sources of fecal pollution and the impact the site on the surrounding waters. Analyses for total coliform, fecal coliform, enterococci and coliphage were conducted throughout the site. High levels of coliform bacteria were found in the groundwater and canals. No enterococci or coliphage were detected. Levels of coliforms were highest where large amounts of yard material had accumulated underground under anaerobic conditions. There was an indication of regrowth of the coliforms within these pockets of rotting organic matter. If fecal material was present, enterococci and coliphage would have been present. Las Olas Isles, Broward County, Florida. A water quality study was conducted in a series of canals connecting intracoastal and ocean water in Ft. Lauderdale, Florida. Levels of E. coli, enterococci, coliphage, Clostridium and Bacteroides were evaluated to detect potential sources of fecal contamination. High levels of E. coli and enterococci alone were sporadic, yet when analyzed in conjunction with hot spots of coliphage they were found to correlate well with suspect areas. Areas adjacent to coliphage hot spots showed gradual decreasing levels in the direction of the receding tide. Conversely, during the incoming tide, elevated coliphage levels penetrated further inland than did E. coli or enterococci. Detection of a point
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Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
source was most successful when all three indicators were abundant at a specific site and surrounded by additional coliphage hot spots in the path of area tidal flow (Davidian, et al. 2001). The PCR assay for Bacteroides fragilis group identified some hot spots of possible contamination in the intracoastal waterways of Ft. Lauderdale, FL. Results from the E. coli and enterococci determinations revealed significant fluctuations in microbial levels between high tide and low tide, while the BFG-PCR and C. perfringens results demonstrated less variation between high and low tide. At low tide, the levels of E. coli were significantly higher in both the surface and the bottom water. The enterococci levels were statistically higher in the surface water but not in the subsurface water. In previous studies on the rivers connecting to the Intracoastal Waterway, it has been demonstrated that the riverbank soil is a source of E. coli (Solo-Gabriele, 2000). This current study demonstrates that as the tide recedes, the E. coli are transported to the Intracoastal Waterway. The PCR results did not indicate that there is a similar environmental source of Bacteroides spp. in the natural environment (Bonilla, et al. 2001). There appears to be multiple sources of the indicator microbes within the Las Olas Isles area. E. coli and enterococci may originate from upstream river water sources and/or from groundwater. Coliphage data suggests that there may be a source near a sewage pump station on Las Olas Boulevard. The stability of Bacteroides and Clostridium suggests that the contamination is diffuse. The data suggests that various indicators are sensitive to different types of contamination and respond differently to different types of environmental stimuli. It is important to select the indicator(s) best suited for a given situation. In this study coliphage enumeration proved to be useful for the detection of recent fecal contamination. In conclusion, one indicator does not provide the entire microbial water quality profile for the Las Olas waterways. This study was conducted by Nova Southeastern University and the University of Miami, and was funded by the City of Fort Lauderdale, Florida. Discussion Recent studies indicate that the various microbial indicators of fecal pollution that have been evaluated in tropical marine waters respond differently to different environmental factors. This suggests that the use of only one individual indicator could mask patterns or trends (problem of regrowth, rapid die-off and false positives). A water manager must survey potential sources of pollution and choose indicators that are appropriate for those sources. The following table compares the microbial indicators used in the described case studies in tropical marine waters.
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Microbial Indicators of Fecal Pollution in Marine Waters in Tropical Regions
Positive and Negative Traits of Some Microbial Indicators Indicator
Positive Traits
Negative Traits
F coli (E. coli)
Accepted freshwater indicator Indicate recent fecal contamination Potential for typing
Regrowth in soil and water Rapid die-off in marine water
Enterococci
More persistent than coliform Used as marine indicator
Regrowth in soil and water
Clostridium
Present in sewage impacted water Settle in sediments Correlated with parasitic protozoa
May come from animal feces May be too conservative Requires anaerobic culture
Bacteroides
High numbers in human feces
Requires anaerobic culture PCR techniques expensive
Coliphage
Method well established Samples may be frozen and shipped Behave like enteric viruses
Not specific to humans Not detectable in fresh feces
References
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DeBartolomeis, J., and V.J. Cabelli. (1991) Evaluation of an Escherichia coli host for enumeration of F Male-Specific Bacteriophages. Applied and Environmental Microbiology, Vol.. 57, pp1301-1305. Fujioka, R.S. (1997) Appropriate recreational water quality standards for Hawii and other tropical regions based on concentrations of Clostridium perfringens. Proceedings of the 70th Annual Conference & Exposition of the Water Environment Federation, Vol. 4, pp 405-411. Griffin, D.W., Gibson, C.J., Lipp, E.K., Riley, K., Paul, J.H., and J.B. Rose. (1999) Detection of viral pathogens by reverse transcriptase PCR and of microbial indicators by Standard Methods in the canals of the Florida Keys. Applied and Environmental Microbiology, Vol. 65, pp 4118-4125. Kreader, C.A. (1995) Design and evaluation of Bacteriodes DNA probes for the specific detection of human fecal pollution. Applied and Environmental Microbiology, Vol. 61, pp 1171-1179. McCorquodale, D. S. and C. M. Burney. (1996) Indicators for the determining the sources and extent of fecal contamination in coastal waters: An annotated bibliography. Broward County Department of Natural Resource Protection, Technical Series. McFeters, G.A. and A. Singh. (1991) Effects of aquatic environmental stress on enteric bacterial pathogens. Journal of Applied Bacteriology Symposium Supplement, Vol. 70, pp 115S-120S. Paul, J.H., Rose, J.B., Jiang, S., Kellogg, C., and E.A. Shinn. (1995) Occurrence of fecal indicator bacteria in surface waters and the subsurface aquifer in Key Largo, Florida. Applied and Environmental Microbiology, Vol. 6, pp 2235-2241. Pettibone, G.W. and J.J. Cooney. (1986). Effect of organotins on fecal pollution indicator Organisms. Applied and Environmental Microbiology, Vol. 52, pp 562-566. Ricca, D.M. and J.J. Cooney. (1998) Coliphages and indicator bacteria in Boston Harbor, Massachusetts. Environmental, Coastal and Ocean Sciences Program, Univ. of Massachusetts Boston, pp 404-408. Rose, J. B., X. Zhou, D. W. Griffin and John Paul. (1997) Comparison of PCR and plaque assay for detection and enumeration of coliphage in polluted marine waters. Applied and Environmental Microbiology, Vol. 63, pp 45644566. Author: D. S. McCorquodale, Jr. Spectrum Laboratories, Inc., Fort Lauderdale, Florida and Oceanographic Research Center Nova Southeastern University, Fort Lauderdale, Florida
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Drinking Water Quality Monitoring, The Cayman Islands Perspective by Antoinette Johnson, Department of Environmental Health, Cayman Islands Government Abstract Potable water in the Cayman Islands is provided by a number of sources with 90% of residents having access to piped water. However, only 72% of householders cite the piped supply as their primary source. This paper examines the results of the drinking water quality monitoring programme of the Department of Environmental Health (DEH) over the years 1996 – 2000. Samples were collected from higher risk establishments in the three islands, analysed for bacterial quality and assessed using the World Health Organization Guidelines (1993) and DEH policy. Sample results were divided into piped (point of use samples) and non-piped sources with 90% of piped water samples (point of use) over the five years testing satisfactory compared to only 40% of non-piped supplies. Approximately 30% of samples collected by the DEH over the five-year period were from non-piped supplies Reasons for the continued use of these alternative sources in areas where safer piped water is available are considered. Key Words: drinking water, piped, thermo-tolerant coliform Introduction The Cayman Islands includes the three islands of Grand Cayman, Cayman Brac and Little Cayman with a population of 39,020 as of the last census in October 1999. Drinking water in the Cayman Islands is supplied by a variety of sources including groundwater, rain water catchment, two municipal suppliers, private reverse osmosis plants, two bottled water companies and bottled water imports. While the greater part of Grand Cayman and part of Cayman Brac is now serviced by a piped water supply, the remaining areas of the islands still rely on other methods. Even in those districts where the piped supply is available, cost or other considerations may factor into the consumer’s decision on (1) whether or not connect to the municipal water supply, or (2) even if connected, how much is consumed. Both companies that supply piped water in Grand Cayman and Cayman Brac use reverse osmosis. This can be a costly process and in the Cayman Islands results in rates of between CI $15 and CI $19 per thousand gallons for domestic consumers and CI $18 and CI $19 per thousand gallons for commercial customers. Due to higher energy costs in Cayman Brac rates are higher there at approximately CI $21 per thousand gallons for both domestic and commercial customers (Water Authority Cayman Rate Sheet, 1998; Cayman Water Company Rate Sheet, 2001). In the early seventies, piped water was introduced to the district of West Bay on Grand Cayman. The Cayman Water Company now supplies the district of West Bay and the Seven Mile Beach area. In 1988, the Water Authority Cayman started the pipeline that by
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2001 extended from George Town to Gun Bay in East End (H-J van Genderen, WAC, pers. comm. 2001). In Cayman Brac, the Water Authority supplies piped water to a 6 km pipeline in the West End of Cayman Brac. In Grand Cayman and Cayman Brac, the volumes of desalinated water sold have shown a steady increase over the past five years (See Figure 1) as population has increased and the pipeline extended eastward on Grand Cayman. According to the last census in 1999, it was estimated that nearly 90% of the population of the Cayman Islands lived in areas with access to piped water. However, only 72% of households surveyed then used the mains supply as their primary source of water.
Figure 1. DAILY WATER SALES IN THE CAYMAN ISLANDS 6,000
Volume Water Sold (cubic metres/day)
5,000 4,000 3,000 2,000 1,000 0 1996 WAC
CWC
1997
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Data supplied by Water Authority-Cayman (Annual Reports)
Moreover, many older buildings have wells and cisterns in addition to the more recent piped water systems. While the information on the percentage of households or business using sources other than the piped supply is not available, anecdotal evidence suggests that a significant percentage do employ dual systems. These dual systems may be utilized by switching back and forth as needs arise or by using the non-piped supply for flushing toilets, showering, gardening and other domestic purposes. Under its mandate to “monitor and control any environmental conditions which may adversely affect human health”, the Department of Environmental Health (DEH) is responsible for ensuring that the drinking water in the Cayman Islands is wholesome and poses no risk to the population. As part of this responsibility, the DEH conducts a routine monitoring programme which collects samples at point-of-use for a number of establishments considered as higher risk. These include schools and day care centres, homes for the elderly, government hospitals and clinics and government office buildings.
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In addition, all food establishments and tourist accommodations are sampled at minimum once per year, and a satisfactory water sample is a requirement of licensing approval. The rationale for collecting at point-of-use rests on the finding that even in the presence of satisfactory chlorine levels in the municipal supply it was possible to obtain unsatisfactory levels of bacteria in the water sampled at the tap. Moreover, in some cases, the consumer was not certain as to the source. The responsibility of the DEH is to ensure the public safety and hence the emphasis of the monitoring programme is on the water used rather than that supplied. Under this monitoring programme, samples collected at the point-of-use are examined for bacterial water quality according to World Health Organization Guidelines for Drinking Water Quality as defined by total coliform and thermo-tolerant coliform counts (WHO, 1993). Methods Water samples are collected by the DEH: as monthly samples from approximately 150 routine monitoring sites; annual or more frequent samples collected at food establishments and tourist accommodations; or in response to consumer complaints. Samples are collected at point-of-use, i.e. at kitchen taps, hand wash sinks, water coolers etc. According to WHO guidelines the minimum sampling frequency is 1 sample per 5000 population monthly. However, these guidelines also suggest taking into consideration any increased risk of contamination due to cross-connections and back siphonage as well as the un-piped supplies and untreated water (WHO, 1993). Taking these factors into consideration, the result was some 2500 water samples collected and analysed by the DEH in 2000. Samples were collected and analysed according to the Standard Methods for Water and Wastewater for coliform and thermotolerant coliform organisms, using the membrane filtration method. In addition, free chlorine readings were taken at the site at the time of sampling (Standard Methods, 19th Edition). Results are assessed according to the WHO guidelines for water intended for drinking which specifies that no E. coli or thermotolerant bacteria must be detectable in any 100 ml sample. For treated water in a distribution system, WHO additionally specifies that total coliform bacteria must not be present in any 100 ml sample or in 95% of the samples take throughout a 12-month period. (WHO, 1993) Piped water samples that do not meet these guidelines are submitted at minimum to a resample. If results continue to be unsatisfactory, then a sanitary investigation is warranted. In addition, samples that show a significant number of non-coliform bacteria are also submitted to further scrutiny. (Non-coliform bacteria are defined by the Environmental Health Laboratory as those bacteria that do not show the positive reaction as defined in the total coliform or thermotolerant coliform membrane filtration test but that do grow on the same plate.) There are two reasons for this stance: the first is that the
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presence of a large number of other organisms on the membrane filter may mask a positive result. Secondly, chlorination may result in the suppression rather than elimination of coliform bacteria and hence affect their ability to give a positive reaction in the 24-hour membrane filtration tests. While there are methods for the resuscitation of such bacteria as outlined in Standard Methods, the DEH laboratory does not routinely carry out this type of pre-analysis procedure on drinking water samples. In the absence of adequate chlorination, suppressed coliform bacteria may subsequently recover. Thus samples with significant numbers of other non-coliform bacteria are therefore assessed as borderline, i.e. satisfactory as to WHO Guidelines but warranting further examination according to DEH internal policy. Non-piped supplies which do not meet WHO or DEH guidelines are recommended for further action such as the cleaning or disinfection of cisterns, tanks, and bottled water coolers. If the sample is from a well (groundwater) it is recommended that the water be treated before potable use. Results (1) Piped vs. Non-Piped Supplies Results of analysis are presented for the years 1996 through 2000. Non-piped sources include cisterns, wells, tanks, locally bottled water and reverse osmosis plants. Piped sources include the two piped water suppliers on the islands and results refer to samples collected at point-of-use. These results demonstrate that the piped water samples are consistently safer than the other sources with a mean 90% of piped water samples assessed as satisfactory compared to 40% for non-piped sources. (Table 1, Figure 2 and 3) Table 1: Results of bacterial analysis on water samples collected 1996 - 2000 Year
Satisfactory Unsatisfactory Borderline (No. of samples) Piped Supplies (Collected at Point-of Use) 1996 598 41 4 1997 1025 29 18 1998 1123 134 66 1999 1285 69 35 2000 1456 201 102 5-Year Mean Non-Piped Supplies (Collected at Point-of-Use) 1996 143 250 12 1997 195 212 119 1998 131 249 108 1999 251 115 85 2000 307 245 119 5-Year Mean
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% Satisfactory
93 96 85 93 83 90 35 37 27 56 46 40
Drinking Water Quality Monitoring, The Cayman Islands Perspective
Figure 2 Bacterial Quality of Piped Water Samples (1996 - 2000) 1600
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1000
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600
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200
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1997
1998
1999
2000
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Unsatisfactory
Satisfactory
* Samples collected at point-of-use
Figure 3. Bacterial Quality of Non-Piped Water Samples (1996 - 2000) 350
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* Samples collected at point-of-use
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Drinking Water Quality Monitoring, The Cayman Islands Perspective
(2) Effects of Free Chlorine The data for the year 2000 is presented as an example to demonstrate that even with adequate chlorination in piped supplies it was possible to get unsatisfactory samples. (Table 2) Table 2: Bacterial quality of cistern and piped water showing the relationship with free chlorine levels measured at site. All results refer to water samples collected at point-of-use. Free Chlorine (mg/l) Cistern 0 (None Detected) 0.1 (Detection Limit) 0.2 – 0.5 (WHO Guideline) > 0.5 Piped Supply 0 (None Detected) 0.1 (Detection Limit) 0.2 – 0.5 (WHO Guideline) > 0.5
Satisfactory
Unsatisfactory
Borderline
76 12 73 47
133 4 11 2
56 2 11 1
180 166 926 5
32 34 102 0
15 13 63 1
In some cases resampling established that the problem was temporary, and due to sampling or analytical error or perhaps work on the pipeline. In a few cases, however, there were repeated unsatisfactory results of water samples collected at point-of use from piped supplies, even in the presence of adequate chlorine residuals. In these cases, further investigation often identified one of the following reasons for the problem: · There were cross linkages to another source – either cistern or well - and although the alternate source may have been designated for non-potable purposes, leaky or open valves resulted in mixing of the two supplies. · An alternate supply using the same lines may have been switched on for a short period to carry out a specific purpose, e.g. filling a washing machine, but was so contaminated that when the supply was switched back to the piped water, the lines were still contaminated enough to give an unsatisfactory result. In the case of cisterns it was found that the results of analysis were more dependent on whether a cistern was clean and free of debris than if the cistern had been recently treated. Since the sampling method requires the use of a chlorine neutralizing agent in the sampling bottles, results are true indicators of the bacterial load at the time of sampling (Standard Methods 19th Edition, 1995). (3) Use of alternative sources. In spite of the fact that nearly 90 % of the population has access to piped water, only 72 % of householders listed it as their main water source. The DEH monitoring programme targets
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mainly public and commercial establishments but figures are similar with 26 % of water samples in 1999 collected from non-piped sources and a mean of about 30 % over the 5 years assessed. Some of the reasons given by consumers for using alternate sources are: · Cost – For commercial establishments where utilities constitute a significant portion of their overhead, cost is a prime consideration. Some larger establishments operate their own reverse osmosis plants, five under license from the Water AuthorityCayman and two independent operations. (H-J van Genderen, WAC, pers. comm., 2001). Cost is also an issue for domestic consumers, with more persons opting to use cisterns during the rainy season. The problem with this is that few consumers clean or maintain their cisterns adequately and the water collected by rainwater catchment from the roof may be contaminated with bacteria. In fact, older residents refer to a phenomenon known as “change of water time” where it is expected that at the onset of the rainy season, there is spike in the number of persons affected by gastrointestinal illnesses. · Taste, preferences – Some persons find the taste and odour of the piped water unsatisfactory. We have found that as a population, Cayman Islanders are more sensitive to chlorine and dislike the taste in water. Several offices and homes are switching to bottled water for drinking for this reason. However, we have also found that if bottled water coolers are not properly maintained, numbers of bacteria can reach unsafe levels. Secondly, piped water tends to be higher in chloride than cistern water. For those consumers used to the low chloride levels of rainwater, the perceived “brackishness” of piped water is a deterrent. · Perception of safety and quality – Piped water has been available in the West Bay area of Grand Cayman less than 30 years. In George Town, the main population and commercial centre, this period is even shorter at 13 years. As a result, especially for the older residents, there is a reluctance to switch from a known and trusted source to a new one, especially one that costs much more. Conclusions · ·
·
While the majority of the population of the Cayman Islands now has access to piped water, not all avail themselves of the opportunity, and if they do so, may not do so exclusively. Piped supplies sampled at point-of-use in the Cayman Islands can be considered safe, as 90% of samples collected tested satisfactory for bacterial water quality. While this number falls short of the WHO recommendation of 95% of samples annually (WHO 1993), the factors of sampling at point-of-use, possible cross-contamination from unsatisfactory sources and the sampling and handling error may account for the shortfall. The DEH monitoring programme collects well in excess of the numbers of samples suggested by WHO for normal piped supplies (WHO 1993). However, the availability of the various sources and the uncertainty of knowing for sure which is being used require that samples be collected at least monthly at high-risk establishments. Since samples are collected randomly within each month, this
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·
increases the possibility of identifying problems caused by seasonality and consumer decisions. Public education on the importance of safe drinking water is essential in ensuring that residents of the Cayman Islands not only have access, but also utilize safe water supplies. In conjunction with such agencies as the Water Authority Cayman, the Public Health Department and the water producers, the DEH will continue provide information to educate the public in making sound decisions on their choices for drinking water.
References ·
World Health Organization (1993) Guidelines for Drinking Water Quality, 2nd Edition Volume 1, Recommendations.
·
APHA Standard Methods for the Examination of Water and Wastewater (1995), 19th Edition. Eaton, Andrew D., Clesceri, Lenore S. and Greenberg, Arnold E. Editors.
·
Cayman Islands Statistics Department. The Report of the Cayman Islands 1999 Population and Housing Census.
·
Water Authority-Cayman (1996, 1997, 1998) Annual Reports of the Water Authority of the Cayman Islands.
Author: Antoinette Johnson, Department of Environmental Health, Cayman Islands Government Tel: (345) 949-2454 Fax: (345) 949-4503 E-mail :
[email protected]
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E. coli 0157:H7, A Deadly Emerging Waterborne Pathogen by Jennifer L. Clancy, Ph.D. Clancy Environmental Consultants, Inc.
Abstract E. coli 0157:H7 is a pathogenic strain of E. coli that produces cytotoxins and causes serious disease in humans. First recognized as a unique strain of E. coli in an outbreak of foodborne illness in 1982, it is now recognized as a serious emerging pathogen in both food and water. Sources are cattle and other animals, and sewage. E. coli 0157:H7 is associated with eating undercooked beef, but has caused disease in contaminated cider, raw milk, fruits, salad vegetables, yogurt, mayonnaise, salami, recreational water and drinking water. Symptoms of the disease caused by E. coli 0157:H7 range from a mild non-bloody diarrhea to severe bloody diarrhea (hemorrhagic colitis), sometimes resulting in hemolytic uremic syndrome (HUS) can lead to renal failure. Secondary spread has been noted in many outbreaks. Young children (<5 years) are particularly susceptible, as are the elderly. The pathogenesis of the disease is still unclear. Studies indicate that the infectious dose is as low as 10 organisms. The recommended treatment is supportive therapy (rehydration, dialysis) as opposed to antibiotic therapy, which may exacerbate the progression of the disease to HUS. There have been hundreds of cases reported worldwide attributed to both food and water. Several outbreaks have been associated with recreational water (pools, fountains). The notable North American waterborne disease outbreaks from tap water include: Cabool, Missouri in 1989 – 243 cases, 4 deaths; Alpine, Wyoming in 1998 – 114 cases, no deaths; Greenwich, New York in 1999 - 781 cases, 2 deaths, and Walkerton, Ontario, Canada in 2000 – 2300 cases, 7 deaths. These outbreaks occurred in public water systems that were meeting the drinking water standards for total coliform bacteria and turbidity at the time of the outbreak. All were small groundwater systems where contamination occurred as a result of intermittent or no treatment. The paper discusses the outbreaks and provides treatment and monitoring recommendations to avoid these contamination events from occurring in the future. Key Words: E. coli 0157:H7, water treatment, disinfection, waterborne disease outbreaks Introduction E. coli is generally considered a harmless commensal bacterium found in the gut of all warmblooded animals. It is not considered a pathogen except under certain conditions where it gains entry into the host and causes infection under unusual conditions (e.g. weakness in the immune system). Bacteria that are not normally pathogens but can cause disease in special circumstances when the opportunity arises are known as opportunistic pathogens. E. coli 0157:H7 is one of several pathogenic strains of E. coli that produce cytotoxins and causes serious disease. E. coli 0157:H7 was first recognized as a human pathogen in 1982 (Reilly et
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E. coli 0157:H7, A Deadly Emerging Waterborne Pathogen
al, 1983). E. coli 0157:H7 is one of a group of E. coli known as verotoxin-producing E. coli (VTEC). E. coli 0157:H7 is one of over 100 serotypes of VTEC. Within the 0157 serotype, a small group of isolates (3%) have antigens other than the H7 antigen, and about 12% do not have the H antigen at all and are referred to as E. coli 0157:NM (Strockbine et al, 1998). Through active surveillance by public health professionals, infection with E. coli 0157:H7 is now recognized as an important public health problem in the developed world due to its increasing incidence. Approximately 10% of infected individuals in outbreaks and family studies are asymptomatic, that is, infected but showing no signs of disease (Dundas and Todd, 2000). Human infections have been reported in over 30 countries on six continents, with Scotland, Canada, and the US reporting the highest disease incidences (Reilly, 1997). In the US there has been a yearly increase in the number of outbreaks, but it is not possible to determine if this is a genuine increase in disease incidence or is due to better detection and reporting (Griffin, 1995). The majority of outbreaks in the US and UK have been due to foodborne illness, often from eating undercooked beef. Other modes of infection include transmission through water (recreation and drinking water), contact with animals, and person-to-person spread. Secondary spread, the spread of infection from persons initially infected from a particular source to others, is an important route of infection. During the large hamburger-associated outbreak in the US in 1993, 11% of the identified cases were secondary (CDC, 1993) Occurrence in Animals and Humans E. coli 0157:H7 has been isolated from a variety of animals including dairy and beef cattle, sheep, pigs, goats, horses, deer, rats, pigeons, and seagulls (Chapman, 2000; Cizek et al, 2000). E. coli 0157 does not seem to cause any obvious clinical symptoms in cattle and usually colonization is for a short duration, often less than two months (Hancock et al, 1998). A number of studies have examined carriage rates in herds. In the northern US, prevalence of E. coli 0157:H7 infection in cattle has been shown to range from 1% to 9.5% (Ostroff et al, 1990; Shere et al, 1998). In Ontario, the prevalence of VTEC infection is estimated to be 9.5% for cows and 24.7% for calves (Wilson et al, 1992; Wilson et al, 1993), supporting the hypothesis that age affects carriage rate in cattle. The farm-level prevalence of pathogenic E. coli ranges from 41% to 50% (Clark and Grayman, 1998; Waltner-Toews et al, 1986), where a prevalence rate of 41% has been observed in Holsteins in southwestern Ontario. Ontario on-farm infection rates range from 0-60% for cows and 0-100% for calves, with VTEC demonstrated to persist in herds for up to two years (Shere et al, 1998). Chapman et al (1997) showed that at slaughter the prevalence of E. coli 0157:H7 in samples of cattle feces was between 4.8% and 36.8%. The wide variation in carriage rates of E. coli 0157 may be explained partly by the variable efficiencies of the isolation methods used by different investigators and the transient nature of carriage in cattle. Human carriage of E. coli 0157:H7 was studied in Sweden in three large meat-processing plants (Stephan et al, 2000). A prospective study was carried out between October 1997 and May 1999 by collecting and analyzing 5590 stool samples from workers. The study found that 3.5% of the stool samples were positive for verotoxin-producing E. coli 0157:H7 in 452
E. coli 0157:H7, A Deadly Emerging Waterborne Pathogen
asymptomatic carriers. This carriage rate is far higher than for other pathogens relevant to food hygiene. Stephan and Untermann (1999) have predicted the prevalence of asymptomatic carriers in slaughterhouses to be as high as 9% due to increased exposure and exposure to higher numbers of VTEC organisms. A study of Canadian dairy farm families showed 6% of the individuals to be VTEC carriers (Wilson et al, 1996). Transmission and Survival of E. coli 0157:H7 E. coli 0157:H7 can be transmitted through various routes to cause infection. These include: transmission from animals to humans by direct contact with animals or animal manure; person-to-person transmission, foodborne transmission, and transmission through contaminated recreational or drinking water. Contaminated Food Since it was first recognized as a pathogen in 1982, E. coli 0157:H7 has become one of the most significant foodborne pathogens (Meng and Doyle, 1998). A variety of foods have been identified as vehicles of E. coli 0157:H7-associated illness: ground beef, roast beef, venison jerky, salami, raw milk, yogurt, lettuce, unpasteurized apple cider or juice, cantaloupe, potatoes, radish sprouts and alfalfa sprouts. The largest foodborne outbreak occurred in Osaka, Japan in 1996 when 6000 school children became infected (Michino et al, 1998). E. coli 0157:H7 has an unusual tolerance to high acid content which allows it to survive in some foods. Food previously considered safe and ready to consume due to high acidity, such as apple cider and dry-cured salami, have been vehicles of outbreaks. Storage temperature, pH, salt content, and water activity are major factors affecting survival and growth of VTEC in food. Undercooked beef is the most commonly recognized means of transmission. Person-to-Person Transmission Person-to-person transmission can occur by direct contact or by the fecal-oral route, i.e. when changing diapers of infected children in homes or daycare centers. The low infectious dose makes this route of transmission difficult to control unless scrupulous handwashing is practiced. It is not always possible to practice the degree of hygiene necessary to disrupt the chain of pathogen transmission in a household where young children are ill with diarrhea. Two outbreaks occurred in hospitals in the UK in 1990 and 1992 that were attributed to person-to-person transmission. In 1995 person-to-person transmission was responsible for an outbreak in North Wales in a nursery. One of the important aspects in the epidemiological investigation of an outbreak where person-to-person spread is possible is determining which cases are primary (those who acquired the infection from a source(s) in the outbreak) and which are secondary (the result of person-to-person spread from the primary cases. Manure and Soils E. coli 0157:H7 can enter the environment in animal feces shed directly onto the land. Cattle and sheep are considered to be an important source of environmental transmission. Animal wastes can contain up to 106 E. coli 0157:H7 per gram of feces, and these organisms can 453
E. coli 0157:H7, A Deadly Emerging Waterborne Pathogen
survive in manure piles for months. These wastes can serve as an important route of disease transmission. E. coli 0157:H7 can also enter the environment in animal wastes (manure), septic tank contents, and slaughterhouse wastes (Maule, 2000). E. coli 0157:H7 can survive for long periods in soil. Maule (1999) inoculated laboratorybased soil and grass microcosms with E. coli 0157:H7 and found the test organisms still detectable in high numbers after 130 days. E. coli 0157:H7 has been shown to survive inside soil protozoa (Acanthamoebae polyphaga), indicating that this protozoan may serve to disseminate E. coli 0157:H7 and allow it to survive in the environment. There have been at least two incidences of food poisoning caused by eating or handling vegetables contaminated with soil containing E. coli 0157 (Morgan et al, 1988; Cieslak et al, 1993). These outbreaks illustrate that E. coli 0157 can survive long enough in sufficient numbers in soil to transfer to and infect humans (Maule, 2000). Fresh produce is now well recognized as a significant source of E. coli 0157; 14% of E. coli 0157 outbreaks in the US since 1982 were linked to fruits and vegetables (Anonymous, 1997). Several researchers have studied survival of E. coli 0157 in animal wastes and feces. Cattle and sheep artificially infected with E. coli 0157 were shown to contain up to 106 organisms per gram of feces (Wang et al, 1996; Kudva et al, 1998). There appears to be considerable variability in rates of excretion, and seasonal variability, with peaks of excretion in warm weather. Kudva et al (1998) describe survival of E. coli 0157 in manure and manure slurry. They found that E. coli 0157:H7 survived for extended periods in manure piles under farm conditions. In sheep manure, isolates of E. coli 0157 survived for 21 months at levels from <102 to 106 per gram feces. An E. coli 0157 positive bovine manure pile was culture positive for 47 days. When manure piles were aerated by mixing, there was a decline in E. coli 0157 survival. It was suggested that the decline in numbers in aerated feces was due to drying. E. coli 0157 was not recovered from the dry top layer of manure piles, another indication of the susceptibility of this organism to drying or exposure to light. Wang et al (1996) showed that incubation temperature and inoculum levels had a significant effect on survival in feces. Higher levels of E. coli 0157 persisted when the initial inoculum was higher and samples were held at lower temperatures. However, the levels found to persist were high, in the range of 103 to 105 per gram of feces. An outbreak occurred in June 1997 in the UK after a large music festival held on a dairy farm. The people affected had camped on the land on which 600 dairy cows had grazed recently. Water A number of outbreaks have been associated with transmission of E. coli 0157 via water, including recreational and drinking water. Survival of E. coli 0157 in water appears to be prolonged, even though the aquatic environment is seemingly unsuitable for a gastrointestinal bacterium. Hancock et al (1998) found that E. coli 0157 survived for up to four months in
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water troughs on farms. When a strain of E. coli 0157 was inoculated into pond water it survived for 21 days at 13°C, indicating that water troughs and ponds may play a role in transmission of E. coli 0157 in farm animals (Porter et al, 1997). Experiments by Rice et al (1992) were conducted to determine the persistence of E. coli 0157 strains in drinking water. The water used in the study was taken from the system in Cabool, MO where a waterborne outbreak occurred in 1989-90. In this outbreak, over 240 people were infected and four died (Geldreich et al, 1992). When the water samples were incubated at 20°C two strains of E. coli 0157 survived for more than 40 days. At 5°C the cell death rate was much less and large numbers (103 CFU mL-1 of an initial inoculum of 106 CFU mL-1) were still detectable after 70 days. Wang and Doyle (1998) determined the persistence of 103 CFU mL-1 of a mixture of five strains of E. coli 0157 in samples of potable, reservoir, and lake water at 8°C, 15°C, and 25°C. Persistence of E. coli 0157 was consistently longer at lower temperatures. At 8°C a 100-fold increase in viable numbers of E. coli 0157 over a 91-day incubation period was observed. In some lake water samples held at 15°C and 25°C, cell numbers fell to undetectable levels in 14-21 days. In municipal water samples, survival was greatest where there was minimal competition from other microorganisms (Maule, 2000). A study by Lisle et al (1998) showed that E. coli 0157:H7 was made significantly more resistant to chlorine disinfection when it was held under starvation conditions such as suspension in natural water. The strain used in the study developed resistance to chlorine concentrations up to 0.5 mg/L, a level significantly higher than the detectable disinfectant residual level mandated for drinking water distribution systems in the US. Detection of E. coli 0157 in Water It is difficult to detect E. coli 0157 in water for several reasons. The concentration of organisms may be low, and sublethal injury of cells may occur due to osmotic pressure changes in the aquatic environment. Special techniques must be used to enhance recovery of E. coli 0157 in water samples. This includes a pre-enrichment step after initial concentration by membrane filtration to allow recovery of injured organisms, followed by a special immunomagnetic separation step to separate the E. coli 0157 from other E. coli (Chalmers et al, 2000). Routine drinking water tests for total coliforms and E. coli do not always detect E. coli 0157. Several commonly used test methods are based on detection of the enzyme ß-glucuronidase, which is found in the majority of E. coli strains. In those methods, E. coli is identified based only on the presence of this enzyme (APHA, 1998). However, E. coli 0157 does not possess this enzyme and samples containing E. coli 0157 will appear negative in tests based upon detection of ß-glucuronidase (De Boer and Heuvelink, 2000). This means that routine water testing for compliance under the Total Coliform Rule could yield satisfactory bacteriological results when in fact E. coli 0157 is present. If a water sample is suspected to contain E. coli 0157, specialized detection methods must be used to recover it. However, even when specialized techniques are used, recovery and detection in water remain elusive.
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Disinfection Chlorination of water supplies is very effective against most bacteria and many viruses when applied to relatively high quality water. Chlorination of microorganisms is most easily described using a relationship between chlorine concentration (in mg/L) and contact time (in minutes) known as the CT value. CT relationships are developed under stringently controlled laboratory conditions, and when applied to real world situations often require a great deal of judgment and past experience. White (1972), Jarroll (1981), and Rice et al (1982) have all developed CT value tables for a range of common pH values. The United States Environmental Protection Agency (USEPA) published CT tables for Giardia and virus inactivation in the Surface Water Treatment Rule (SWTR). The effectiveness of chlorination depends on several water quality parameters including pH, temperature, contact time, turbidity, chlorine concentration, and chemical content (organic and inorganic materials) of the water. These factors contribute to the chlorine demand, i.e. the difference between the amount of chlorine added to the water and the amount of residual chlorine remaining at the end of a specified contact period. Those factors that contribute to the demand ‘use up’ the chlorine so that it is not available for disinfection. It is the free chlorine residual (what remains in the water after demand is met) that disinfects. While some microorganisms will be inactivated as the demand is being met, this is minimal. When water quality is compromised due to high turbidity or other biological or chemical contaminants, chlorination is less effective due to the demand from these other contaminants in the water. Disinfection potential can be compromised with a variety of disinfectants when particulates are present in the water. Microorganisms are negatively charged particles and tend to aggregate with other particles (particle-associated) in fluids rather than remaining alone in suspension (planktonic). Bacteria aggregated to other microorganisms (i.e. algae, diatoms) or microscopic particulate debris can be shielded from disinfection. Particle-associated microorganisms have been shown to be harder to disinfect as the particles shield them from disinfectants and can exert a disinfectant demand (Emerson et al, 1982; Hoff and Akin, 1986; Berman et al, 1988). Cabool, Missouri - 1989 The first waterborne outbreak of E. coli 0157:H7 in the US occurred in Cabool, Missouri in 1989. There were 243 cases of disease and four deaths (Geldrich et al, 1992). The cause of the outbreak was attributed to sewage contamination of a non-disinfected ground water supply that was subject to water main breaks during winter. Isolates of E. coli 0157:H7 were obtained both from patients and the water supply Swerdlow et al, 1992). Alpine, Wyoming - 1998 In the summer of 1998, a waterborne disease outbreak caused by E. coli 0157:H7 occurred in Alpine, Wyoming. A total of 114 persons were suspected of having E. coli 0157:H7 infections. At least 11 cases of secondary illness were reported which were acquired from
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family members who were previously ill. Confirmed cases were found in six states. Two epidemiological studies undertaken to determine the cause of the outbreak showed that illness was associated with consumption of Alpine tap water. The environmental investigation uncovered three potential sources of contamination of the water supply. No definitive conclusion was made as to the source of the contamination, but a spring that was under the direct influence of surface water (GWUDI) and was not disinfected was a likely source. Alpine had two sources of water – a spring and two drilled wells. Neither source was treated although chlorination equipment had been installed some time previously. The spring was the preferred source as it was gravity fed and did not require pumping, keeping water rates low. The wells were used only in summer when additional water production was needed. The primacy agency, USEPA Region 8, had determined that the spring was not GWUDI, so while disinfection was recommended, it was not required. The town had never used the disinfection equipment after it was installed. After the outbreak was detected and water became a suspected source, a boil water order was put in place and likely prevented additional disease cases. The rapid detection of the outbreak was due to the reporting by several local area physicians to the health department. Once E. coli 0157:H7 was suspected, the Wyoming departments of Health and Agriculture went to Alpine to begin investigating, followed by investigative teams from the US Centers for Disease Control and Prevention (CDC) and USEPA. The water system was disinfected using temporary equipment to shock chlorinate the storage tanks and water lines. Extensive sampling and analysis of the system by the USEPA team failed to recover E. coli 0157:H7 from any of the samples. Genetic fingerprinting of the E. coli 0157:H7 isolates from the stools of infected patients showed it to be the same strain. An investigation of potential sources of contamination of the water supply was conducted. Several factors were noted which could have contributed to fecal contamination of the Alpine water supply. These include 1) the spring source itself which was GWUDI, 2) a cattle corral tap in a feedlot which could have acted as a cross connection, and 3) private wells which may not have been disconnected from the system. In addition, weather and geology could have been contributing factors to fecal contamination. The winter snows were heavy and knocked down the protective fencing surrounding the spring, allowing elk and other wildlife to enter the spring area. The Spring season in Alpine was unusually wet, allowing vegetation to become lush and dense and possibly encouraging grazing animals to remain in the spring area later than normal. A series of earthquakes in Alpine in late June could certainly have caused changes in the local geology. The outbreak investigation never determined how the E. coli 0157:H7 entered the water system, but after the boil orders were enacted followed by continuous chlorination, no further cases occurred. On 5 October 1998, the USEPA notified Alpine that they had determined the spring was GWUDI and required that it be disconnected from the public water supply system. The spring was severed from the system in November 1998. No new cases of disease were reported Clancy, 1998).
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Washington County, Greenwich, New York - 1999 In late August and early September 1999, an outbreak of E. coli 0157:H7 and Campylobacter jejuni infections occurred among attendees at the Washington County Fair in Greenwich, New York. This fair, which has been held in the same location for more than a century, was the source of the largest outbreak of E. coli 0157:H7 in US history. There were 127 cultureconfirmed E. coli 0157:H7 infections and 45 cases of C. jejuni identified. In all, 781 persons were identified with culture confirmed or suspected infections. Seventy-one individuals were hospitalized, 14 cases proceeded to HUS and two people died (Novello, 2000). No single definitive cause of the outbreak was determined, although drinking water from Well #6 was implicated. Potential sources of contamination of drinking water wells included runoff from a manure pile due to unusually heavy rains and septic tank seepage from a dormitory. There were three wells that supplied the fairgrounds; two were chlorinated and the third, Well # 6, was not. Well # 6 was found to contain E. coli 0157:H7 as was the dormitory septic system, which may have been hydraulically connected to the well. Walkerton, Ontario - 2000 The rural community of Walkerton in northern Ontario experienced an outbreak of E. coli 0157:H7 due to the drinking water supply in May 2000. An estimated 2300 individuals were sickened with gastrointestinal disease. Sixty-five were admitted to hospital as a result of infection with E. coli 0157:H7 or Campylobacter. Twenty-seven people developed HUS, and seven deaths were attributed to the outbreak. A public inquiry into the outbreak was ordered by the government to investigate and report on: Circumstances that caused the outbreak leading to hundreds of cases of illness and several deaths in May and June 2000, The cause of the events including the effect, if any, of government policies, procedures, and practices, Any other relevant maters concerning the future assurance of Ontario drinking water safety. The inquiry learned in months of public testimony that the water system suffered from a number of serious deficiencies and adverse microbiological contamination of the system was common. The system had been warned for years about the need to improve performance, but no mandatory control was ever exercised. The well suspected as the source of the outbreak was noted to be vulnerable to surface water contamination for 20 years, but recommended protection measures were not implemented. In addition to a failing system, witnesses testified that chlorine residual monitoring records were falsified and the system often run without chlorination due to the pressure to limit chlorination due to taste. The operators of the system were poorly trained and did not understand the implications of their actions on public health. The full details of this outbreak can be found at www.walkertoninquiry.com. (Anonymous, 2000).
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Summary An overriding similarity in these outbreaks is small system size, inadequate training of operations staff, and lack of proper oversight by regulatory officials. All were considered ground water systems and practiced no disinfection by design (Cabool, Alpine) or inadequate disinfection by practice (Walkerton, Washington County Fair). Each system was regulated differently by governmental oversight bodies, but the result – significant waterborne disease and in many cases deaths – was similar. In the US, regulation of drinking water supplies is a mandate of each state unless the state chooses to forego its control, in which case it reverts to the federal primacy agency, the USEPA. Cabool, MO is regulated by the state of Missouri. Alpine is the unique case where the state of Wyoming has never taken primacy for drinking water regulation, and the regulatory authority is the USEPA regional office, USEPA Region 8. In the New York Washington County fair case, the system fell through the regulatory guidelines – the fair was not considered a public water system since it was in operation for only a few days per year and as such, not subject to NYS regulations. In Ontario, the regulations are guidelines and generally not enforceable unless a negative situation occurs, in which case the province can mandate corrective action. One of the problems is all cases is system size. Small systems are plagued by lack of skilled operators and often by lack of well-trained management. Regulatory bodies frequently tend to ‘look the other way’ on small systems regulation as the systems are poorly funded and often struggling to provide water to consumers. In both Alpine and Walkerton, there were years of historical reports showing that 6the systems were inadequate and required upgrades in treatment. The USEPA (Alpine, WY) and Ministries of Environment and Health (Walkerton, Ontario) did not act upon this information even though repeated sanitary surveys and field report showed the systems to be at risk of waterborne disease. However, it is these very small systems that can and do fall into serious problems leading to public health crises. Operations staff were inadequately trained in proper system operation and did not understand the consequences of improper operation of their system was a factor in all cases. Public pressure to minimize chlorinous taste was a factor in Alpine and Walkerton. Maintaining low water rates were a factor in Alpine which led to increased use of the untreated spring. One interesting note. The US regulations focus on large- (serving >100,000 population) and medium- (10,000 to 100,000 population) size systems. The regulations frequently differ on treatment requirements, monitoring, regulatory compliance, requiring a different and often less burdensome compliance regime for small systems. The idea of focusing on large systems is that since they serve many more people, the public health risk to those served by large systems is greater. On the other hand, medium and large-sized systems have teams of water professionals with expertise in engineering, treatment processes, water transmission and distribution, biology, chemistry, public health, and regulations to oversee and manage the effective operation of the system. Small water systems typically have no such team of professionals; they operate with local staff who generally have multiple duties and who have varying levels, if any, of water treatment training or expertise. For these systems it is imperative to have adequate assistance from regulatory agencies to assure water quality for public health protection. Although the population of Alpine is 420 people, it is located near the Teton Mountains near Jackson, WY, a very popular tourist spot. People regularly drive 459
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through the Jackson area to visit other areas of the western US. Although the water system serves only 420 locals, the outbreak was traced to over 100 people in six states. In Walkerton, the population was 5,000, and nearly half, 2,300 were victims of the outbreak. Small systems cannot be overlooked as significant sources of public health risk simply because they have low populations and limited resources. The regulatory agencies must begin to provide training and assistance to assure that small and large systems are able to provide high quality drinking water to all consumers. References APHA. Standard Methods for the Examination of Water and Wastewater, 20th edition. 1998. APHA, AWWA, and WEF. Washington, DC. Anonymous (1997) Prevention and control of enterohaemorrhagic Escherichia coli (EHEC) infections. Report of a WHO Consultation Geneva, Switzerland 28 April-1 May 1997. Geneva: WHO. Anonymous (2000) The investigative report of the Walkerton outbreak of waterborne gastroenteritis. Bruce-Grey-Owen Sound Health Unit. 10 October 2000. Berman, D.A. E.W. Rice, and J.C. Hoff (1988) Inactivation of particle-associated coliforms by chlorine and monochloramine. Appl. Environ. Microbiol. 54: 507-512. CDC (1993) From the Centers for Disease Control and Prevention. Update: Multistate outbreak of Escherichia coli O157:H7 infections from hamburgers – Western United States, 1992-93. The Journal of the American Medical Association 269, 2194-2196. Chalmers, R.M., H. Aird and F.J. Bolton. (2000) Waterborne Escherichia coli O157. Journal of Applied Microbiology Symposium Supplement 88,124S-132S. Chapman, P.A. Sources of Escherichia coli O157 and experiences over the past 15 years in Sheffield, UK. (2000) Journal of Applied Microbiology Symposium Supplement 88,51S-60S. Chapman, P.A., Siddons, C.A., Cerdan Malo, A.T. and Harkin, M.A. (1997) A year study of Escherichia coli O157 in cattle, sheep, pigs and poultry. Epidemiology and Infection 119,245-250. Cieslak, P.R., Barrett, T.J., Griffin, P.M., Gensheimer, K.F., Beckett, G., Giffington, J., and Smith, M.G. (1993) Escherichia coli O157:H7 infection from a manure garden. Lancet 342, 367. Cizek, A., I. Literak and P. Scheer. (2000) Survival of Escherichia coli O157 in faeces of experimentally infected rats and domestic pigeons. Letters in Applied Microbiology 31,349352.
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Clancy, J.L. (1998) Field Investigation of a Waterborne Disease Outbreak at Alpine, Wyoming. USEPA. Clark, RM and Grayman, WM. (1998) Modelling Water Quality in Drinking Water Distribution Systems. AWWA, Denver. De Boer, E. and Heuvelink, A.E. (2000) Methods for the detection and isolation of Shiga toxin-producing Escherichia coli. Journal of Applied Microbiology Symposium Supplement 88,133S-143S. Dundas, S. and W.T.A. Todd. (2000) Clinical presentation, complications and treatment of infection with verocytotoxin-producing Escherichia coli. Challenges for the clinician. Journal of Applied Microbiology Symposium Supplement 88, 2430S. Emerson, M.A., O.J. Sproul, and C.E. Buck (1982) Ozone inactivation of cell-associated viruses. Applied and Environmental Microbiology. 43:603-608. Geldrich, E.E., Fox, K.R., Goodrich, J.A., Rice, E.W., Clark, R.M. and Swerlow, D.L. (1992) Searching for a water supply connection in the Cabool, Missouri disease outbreak of Escherichia coli O157:H7. Water Research 26,1127-1137. Griffin, P.M. (1995) Escherichia coli O157:H7 and other enterohemorrhagic Escherichia coli. In Infections of the Gastrointestinal Tract ed. Blaserr, M.J., Smith, P.D., Ravdin, J.I., Greensburg, H.B. and Guerrant, R.L. pp.1-11. New York: Raven Press. Hancock, D.D., Besser, T.E. and Rice, D.H. (1998) Ecology of Escherichia coli O157:H7 in cattle and impact of management practices. In Escherichia coli O157:H7 and other Shiga Toxin-Producing, E. coli Strains ed. Kaper, J.B. and O’Brien, A.D. pp.85-91. Washington: ASM Press. Hoff, J.C. and E.W. Akin (1986) Microbial Resistance to Disinfectants: Mechanisms and Significance. Environ. Health Perspectives 69: 7-13. Jarroll, E.L., Bingham, A.K. and Meyer, E.A. (1981) Effect of chlorine on Giardia lamblia cyst viability. Applied and Environmental Microbiology. 41:483. Kudva, I.T., Blanch, K. and Hovde, C.J. (1998) Analysis of Escherichia coli O157:H7 survival in ovine or bovine manure and manure slurry. Applied and Environmental Microbiology 64,3166-3174. Lisle, J.T., Broadway, S.C., Prescott, A.M., Pyle, B.P., Fricker, C. and McFeters, G.A. (1998) Effects of starvation on physiological activity and chlorine disinfection resistance in Escherichia coli O157:H7. Applied and Environmental Microbiology 85,177-186. Maule, A. (1999) Environmental aspects of E. coli O157. International Food Hygiene 9,2123. 461
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Maule, A. (2000) Survival of verocytotoxigenic Escherichia coli O157 in soil, water and on surfaces. Journal of Applied Microbiology Symposium Supplement 88,71S-78S. Meng, J. and M.P. Doyle. (1998) Microbiology of Shiga toxin-producing E. coli in foods. In E. coli 0157:H7 and other Shiga-toxin producing E. coli strains. J.B. Kaper and A.D. O’Brien (eds) ASM Press. Michino, H., K. Araki, S. Minami, T. Nakayama, Y. Ejima, K. Hiroe, H. Tanaka, N. Fujita, S. Usami, M. Yonekawa, K. Sadamato, S. Takaya, and N. Sakai (1998) Recent outbreaks of infections caused by E. coli 0157:H7 in Japan. In E. coli 0157:H7 and other Shiga-toxin producing E. coli strains. J.B. Kaper and A.D. O’Brien (eds) ASM Press. Morgan, G.M., Newman, C., Palmer, S.R., Allen, J.B., Shepard, W., Rampling, A.M., Warren, R.E., Gross, R.J., Scotland, S.M. and Smith, H.R. (1988) First recognized community outbreak of haemorrhagic colitis due to verotoxin-producing Escherichia coli O157 in the UK. Epidemiology and Infection 101,83-91. Novello, A.C. (2000) The Washington County fair outbreak report. New York State Health Department. Ostroff, SM et al. (1990) A statewide outbreak of Escherichia coli O157:H7 infections in Washington State. American Journal of Epidemiology 132:239-47. Porter, J., Mobbs, K., Hart, C.A., Saunders, J.R., Pickup, R.W. and Edwards, C. (1997) Detection, distribution and probable fate of Escherichia coli O157 from asymptomatic cattle on a dairy farm. Journal of Applied Microbiology 83,297-306. Rice, E.W., Johnson, C.H., Wild, D.K. and Reasoner, D.J. (1992) Survival of Escherichia coli O157:H7 in drinking water associated with a waterborne disease outbreak of hemorrhagic colitis. Letters in Applied Microbiology 15,38-40. Reilly, W.J. (1997) E. coli O157 in Scotland-an overview. Scottish Centre for Infection and Environmental Health Weekly Report (Suppl. 1,97-13),4-5. Reilly, W.J., Remis, R.S., Helgerson, S.D., McGee, H.B. Wells, J.G., Davis, B.R., Herbert, R.J., Olcott, E.S., Johnson, L.M., Hargrett, N.T., Blake, P.A., and Cohen, M.L. (1983) Hemorrhagic colitis associated with a rare Escherichia coli serotype. New England Journal of Medicine 308,681-685. Shere JA, Bartlett KJ, Kasper CW. (1998) Longitudinal study of Escherichia coli O157:H7 dissemination on four dairy farms in Wisconsin. Applied and Environmental Microbiology 64:1390-9. Stephan, R., S. Ragettli and F. Untermann (2000) Prevalence and characteristics of verotoxin-producing Escherichia coli (VTEC) in stool samples from asymptomatic human carriers working in the meat processing industry in Switzerland. Journal of Applied 462
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Microbiology 88,335-341. Stephan, R. and Untermann, F. (1999) Virulence factors and phenotypical traits of verotoxinproducing Escherichia coli strains isolated from asymptomatic human carriers, Journal of Clinical Microbiology 37,1570-1572. Strockbine, N.A., J.G. Wells, C. A. Bopp, and T. J. Barrett (1998) Overview of Detection and Subtyping Methods. . In E. coli 0157:H7 and other Shiga-toxin producing E. coli strains. J.B. Kaper and A.D. O’Brien (eds) ASM Press. Swerdlow, D.L., Woodruff, B.A., Brady, R.C., Griffin, P.M., Tippen, S., Donnell, H.D., Geldrich, E., Payne, B.J., Meyer, A., Wells, J.G., Greene, K.D., Bright, M., Bean, N.H. and Blake, P.A. (1992) A waterborne outbreak in Missouri of Escherichia coli O157:H7 associated with bloody diarrhea and death. Animals of Internal Medicine 117,812-819. Waltner-Toews D et al. (1986) An epidemiological study of selected calf pathogens on Holstein dairy farm in southwestern Ontario, Canadian Journal of Veterinary Research 50:307-13. Wang, G., Zhao, T. and Doyle, M.P. (1996) Fate of enterhemorrhagic Escherichia coli O157:H7 in bovine feces. Applied and Environmental Microbiology 62,2567-2570. Wang, G. and Doyle, M.P. (1998) Survival of enterohemorrhagic Escherichia coli O157:H7 in water. Journal of Food Protection 61,662-667. White G.C. (1972) Handbook of Chlorination. For Potable Water, Wastewater, Cooling Water, Industrial Processes and Swimming Pools. Van Nostrand Reinhold Company, New York. Wilson, J.B., Clark, R.C., Renwick, S.A. (1996) Vero cytotoxigenic Escherichia coli infection in dairy farm families. Journal of Infectious Diseases 174,1021-1027. Wilson JB et al. (1992) Risk factors for bovine infection with verocytotoxigenic Escherichia coli isolated from Ontario dairy cattle. Epidemiology and Infection 108:423-39. Wilson JB et al. (1993) Risk factors for bovine infection with verocytotoxigenic Escherichia coli in Ontario, Canada. Preventative Veterinary Medicine 16:159-70. Jennifer L. Clancy, Ph.D. Clancy Environmental Consultants, Inc. P.O. Box 314 St. Albans, VT 05478 USA Tel: (802) 527-2460 Fax: (802) 524-3909 email:
[email protected]
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The Road to Laboratory Accreditation Using ISO/IEC 17025 – A Cayman Islands Case Study by Brenda Mac Aree, MSc MCIWEM Water Authority-Cayman Abstract
Due to changes in the regulatory environment worldwide and the increasing internationalisation of the marketplace, laboratory accreditation that can be recognised around the world will soon be counted as the key to corporate survival. Grand Cayman is no exception to the rule since the increased demand for piped water over the past decade has resulted in an ever-increasing demand on the Water Authority-Cayman Laboratory to provide accurate, timely and reliable monitoring data on the Authority’s water distribution systems. Data credibility and quality assurance have been the focus of the Authority’s management team since the establishment of the laboratory in 1983. It is for this reason that the company voluntarily decided to strive for laboratory accreditation status. This paper will outline the accreditation process, our progress so far and what we have yet to achieve. Keywords: accreditation, ISO/IEC 17025, accuracy, proficiency testing, A2LA. Introduction
In 1983, funded by the United Nations Development Programme (UNDP), the Water Authority Laboratory started out with ‘humble beginnings’ in a small ‘one room operation’ in the Water and Sewerage Project Office, a Government owned three-bedroom house. Space was limited but enough to provide for wet chemical analysis on a limited number of groundwater samples originating mainly from around the capital of the Cayman Islands, George Town. Data was recorded in a simple but adequate hard-backed notebook which served only one important purpose; to document the sample collection date and time, the sample source, the parameter(s) to be analysed and the sample calculations and results. Quality assurance was as important then as it is today with the focus of the Authority’s monitoring programmes being on establishing the state of groundwater used in various parts of the island. The data generated by the laboratory in those early days gave support and foundation for decisions leading to the provision of piped water and public sewerage infrastructure in Grand Cayman. The laboratory continued to play a significant role in supporting several major research projects relating to groundwater and wastewater treatment. Like all relatively new organisations the Water Authority-Cayman (WAC) has gone through a period of continuous change and development in order to keep up with new technologies, remain competitive and provide a consistently safe and reliable water supply to consumers. The laboratory has been ‘part and parcel’ of this change, continuously trying to improve methods and procedures in an effort to prove the laboratory’s credibility and benchmark it against other laboratories locally and overseas. It is through the laboratory accreditation process that the laboratory has been able to achieve the high level of quality assurance that
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exists there today. This paper discusses the accreditation process followed by the Authority to date, the progress so far and what yet has to be achieved. The steps taken by the WAC on the path to accreditation together with a summary of the progress so far is given in the following sections : A. B. C. D.
Selection of an Accreditation Body Selection of an International Standard The A2LA Accreditation Process WAC Laboratory - Progress Towards Accreditation
A.
Selection of an Accreditation Body
WAC management wanted to choose an accreditation process that would best suit the needs of a small organisation and be internationally recognised. Initially management looked at EPA Certification however this was considered to be outside of the organisation’s reach since the Cayman Islands are not a US territory and therefore are outside of EPA’s jurisdiction. ISO 9000 Certification was not considered an option since the certification process did not involve testing the accuracy or proving the credibility of results. ISO 9000 is merely a ‘document what you do and do what you document’ process. The National Environmental Laboratory Accreditation Programme (NELAP) was not considered to be an accreditation option either since the programme was based on USEPA analysis methods. It was then that WAC management turned to the A2LA accreditation process. It was found to be exactly what the organisation wanted! It would give us international recognition, accredit the laboratory according to the provisions of the international standard ISO/IEC 17025 (1999), while at the same time allow it to use its own methods. B.
Selection of an International Standard
All laboratories accredited by A2LA are required to comply with ISO/IEC 17025 (1999). Laboratories are assessed against the full text of this standard. The WAC decided to compile their own document entitled “WAC Compliance Document with ISO/IEC 17025 (1999) so as to ensure that every requirement of ISO 17025 was addressed and documented. General Requirements of ISO/IEC 17025 The general requirements of ISO/IEC 17025 can be divided into two sections, (a) management requirements and (b) technical requirements, which are outlined below: (a) Management Requirements Management requirements involve providing documented information on the following: 1. 2. 3. 4.
Organisation Quality System Document Control Review of Requests, Tenders and Contracts where Applicable
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5. Subcontracting of Tests 6. Purchasing Services and Supplies 7. Service to the Client 8. Complaints 9. Control of Nonconforming Testing and /or Calibration work 10. Corrective Action 11. Preventive Action 12. Control of Records 13. Internal Audits 14. Management Reviews Organisation In the WAC’s case since the laboratory was considered part of a larger organisation the WAC Laboratory had to provide a written statement that the WAC was legally responsible for laboratory operations. It was also necessary to document in some form that laboratory personnel were insulated from work-related undue pressures, which could be seen to compromise the quality of their work. The organisation and management structure of the laboratory had to be documented by means of an organisation chart. Quality System The laboratory had to have a documented and communicated quality system. This meant compiling a quality manual detailing quality objectives and policies. For the WAC this was one of the most time-consuming parts of the accreditation process. Presently the WAC Laboratory Quality Manual consists of a twenty-one page document detailing the laboratory’s quality objectives, quality assurance management policy, corrective and preventive action procedures, qualifications of staff, laboratory equipment lists, data management procedures etc. Document Control Documented procedures must be in place to determine how quality system documents are compiled, numbered, reviewed and approved. This section relates mainly to the documentation of laboratory methods/procedures as defined in the WAC Laboratory Standard Operating Procedures (SOP’s). Each SOP should be clearly identified with an identification number and the date on which the SOP was compiled/revised. Invalid or obsolete documents should be taken out of circulation and stamped accordingly. Amendments to documents must be done according to an agreed procedure. Review of Requests, Tenders and Contracts This applies to laboratories that have specific contracts with individual clients to provide a testing service. In these cases the laboratory would have to show the accrediting body that it had the capability and resources to meet the client’s requirements. This does not apply to the WAC Laboratory at present, as it does not carry out contract work.
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Subcontracting of Tests and Calibrations This refers to cases where the laboratory seeking accreditation subcontracts a portion of its workload for a particular test or part of a test included in its scope of accreditation on an ongoing basis. It would then have to provide to A2LA a copy of the subcontractor’s quality manual, procedures for the tests and a copy of training records for the personnel responsible for the subcontractor’s work. The WAC Laboratory does not subcontract out any of its work. Purchasing Services and Supplies The laboratory is required to identify the inputs to its processes in terms of equipment, materials and services that affect the integrity of its tests and develop appropriate specifications and quality control measures. A2LA require that calibration services be obtained from laboratories accredited to ISO/IEC 17025 or another accrediting body recognised by A2LA. Reference material suppliers should be accredited if possible, and all suppliers of other outside support services and products should have a registered quality system. The WAC Laboratory uses twelve different laboratory suppliers who have provided us with products and reagents for testing for more than ten years. The majority of these suppliers are ISO 9000 approved companies. In order to meet with the requirements of the Standard we have to provide A2LA with a list of all the laboratory’s suppliers, its procedures for ordering and obtaining quotes including procedures for checking and validating the orders once they are received. Most of the laboratory’s suppliers have provided a history of good quality service and this is what A2LA wants to see in the laboratory’s supporting documentation. Service to the Client Some laboratories have written contracts with clients to perform a service. In this case the laboratory seeking accreditation must provide the client with reasonable access to relevant areas of the laboratory for the witnessing of tests performed for the client. Communication with the client should be maintained throughout the work. It is the responsibility of the laboratory to inform the client of any major delays or major deviations in the performance of the tests. The WAC Laboratory has a number of clients, which it deals with on a regular basis however it does not presently have any written contract with any of our client base. If the laboratory experiences problems with a test or there is a delay in communicating the results the client is informed accordingly. Complaints The laboratory must have a policy and a procedure for the resolution of complaints received from clients and other parties. Records should be maintained of all complaints and the investigations and corrective actions taken by the laboratory. If a complaint is received to the WAC about water quality the Customer Services’ department generates a complaint form, which is passed on to the laboratory for processing. The laboratory informs the customer services manager of a mutual agreeable time that the laboratory staff can go out to the customer’s location, accompanied by a meter reader, to investigate the complaint and take the necessary samples. On completion of the investigation the laboratory informs the customer of the analysis results and mails out a laboratory analysis report.
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Control of Nonconforming Testing If after the completion of a test procedure a mistake had been made in so far as the procedure was not carried out according to the documented procedure or SOP then this is classed as a ‘non-conformance’. The responsibility and authority for the management of non-conforming work must be identified. An evaluation of the significance of the nonconforming work is made, corrective actions are taken immediately and if applicable the client is notified. The responsibility for authorising the resumption of work is defined. All laboratories come across ‘non-conforming’ work from time to time such as observing positive growth on negative control plates, incorrect incubation temperatures, expired media, etc. Corrective Action The laboratory must provide documentation on the policy, procedure and the designated authorities for corrective action. The root cause of the problem must be identified including the corrective action deemed appropriate to the magnitude and risk of the problem. Any changes to a process or procedure needs to be documented and implemented. Corrective actions require careful monitoring in the form of a follow up. The WAC Laboratory has a file designated only for Corrective Action Forms. The forms document all of the issues mentioned above. Preventive Action This is not to be confused with corrective action! Preventive actions refer to documented procedures for potential sources of non-conformances. For instance the WAC Laboratory assigns one staff member to record the fridge and incubator temperatures for a one-month period. This ensures that there is continuity in the recording process. The laboratory has also initiated a Quality Control Report document, which details non-conformances to laboratory staff and the Head of Department. This cuts down on future potential non-conformances. Control of Records The laboratory is required to maintain documented procedures for identification, collection, indexing, access, filing, storage, maintenance and disposal of quality and technical records. This includes providing information on retention times for files, back up procedures for electronic data etc. The WAC Laboratory stores all analysis data in both hard copy and electronic form. Note that files are backed up on the network server daily and tapes are stored off site. The current two years hard copy files are stored in a filing cabinet in the laboratory office. All other hard copy files are stored in heavy-duty cardboard boxes in a storage warehouse. Staff that input data electronically are required to insert their initials on to the appropriate section of the spreadsheet where data has been entered. Internal Audits The laboratory is required to be audited internally by trained and qualified personnel who are independent of the activity being audited. The audit should address all components of the laboratory quality system and the findings and corrective actions should be recorded. A follow-up audit is also necessary to monitor identified necessary corrective actions. The WAC Laboratory will schedule an internal audit by the Director of Water Authority-Cayman later on this year.
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Management Review The laboratory’s executive management is required to periodically conduct a review of the laboratory’s quality system and testing activities to ensure their continued suitability and effectiveness and to introduce necessary changes and improvements. The audit takes account of assessments by external bodies, corrective actions, proficiency testing results, etc. The WAC Laboratory will schedule a management review in November 2001. (b) Technical Requirements Technical requirements involve providing documented information on the following: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Personnel Accommodation and Environmental Conditions Test and Calibration Methods and Method Validation Equipment Measurement Traceability Sampling Handling of Test and Calibration Items Assuring the Quality of Test and Calibration Results Reporting the Results
Many of the factors listed above can determine the correctness and reliability of the tests performed by a laboratory. These factors need to be taken into account by the laboratory when developing test methods and procedures, in the training and qualification of personnel and in the selection and calibration of equipment used in the laboratory. Personnel The laboratory needs to employ competent personnel to perform its tests. Technical personnel should have demonstrable knowledge and skills to perform tests. They may be asked to demonstrate tests or specific techniques during an assessment. The qualifications and experience required for senior staff are reviewed during the assessment. Factors to be considered include the technical complexity of tests, the frequency at which specific tests are conducted, the contact that the senior staff maintains with the development of methodology and adoption of new methodology within the laboratory. In all cases senior staff need to demonstrate appropriate understanding of the test areas in which they exercise supervision. In assessing qualifications, the balance between relevant academic qualifications and test experience is considered in the light of the range, complexity and accuracy required. In addition the laboratory is required to maintain current job descriptions for all laboratory staff. The WAC Laboratory has compiled a list of the above requirements including staff resumes in the WAC Quality Manual. Accommodation and Environmental Conditions Laboratory conditions for testing i.e. lighting and environmental conditions (dust, temperature etc.) should be such as to facilitate the correct performance of tests. The laboratory has to control and monitor environmental conditions as required by the relevant method or procedure. In the case of microbiological testing, for example, incubation
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
temperatures and the sterility of the surrounding environment is crucial. Measures should be taken to prevent cross contamination. In addition access to and use of areas affecting the quality of tests should be controlled. The WAC Laboratory separates areas used for microbiological and wet chemistry testing. Entry to the laboratory is restricted to laboratory staff and senior staff only who have a special access code for the door. Test and Calibration Methods and Method Validation The laboratory must use appropriate test methods and procedures for tests within its scope. These include sampling, handling, transport, storage and preparation of the items to be tested and where appropriate an estimation of the measurement of uncertainty as well as statistical techniques for the analysis of test data (UKAS, 2000). All methods whether standard or nonstandard methods have to be properly documented and validated. The WAC Laboratory uses an SOP template document on which all other SOP’s are derived. This provides continuity and consistency to our documentation system. Methods are validated by performing tests using commercially prepared reference standards in place of the sample. The laboratory also validates tests by its participation in the Aquacheck (WRc) Proficiency Testing Scheme. Equipment The laboratory is required to have a list of equipment used for testing and documented procedures specifying how the equipment is maintained and calibrated. Instrument log-books should include the instrument serial number, information on how the instrument is operated and maintained in addition to records of calibrations and repairs. All out-of-service equipment must be isolated and identified. The WAC Laboratory maintains an up-to-date file on all testing equipment. Repair reports are filed with the equipment instruction manual. Calibrations performed on TDS, pH, EC meters are logged separately in an instrument calibration book. Measurement Traceability The laboratory is required to have an established programme and procedure for the calibration of its equipment (A2LA, 2000). This includes a system for selecting, using, calibrating, checking, controlling and maintaining measurement standards, reference materials used as measurement standards and measuring and test equipment used to perform tests. All calibration of testing equipment should be made to SI units. Currently the WAC Laboratory uses only NIST traceable reference standards for calibration. Balances are sent back to the manufacturer once every two years for complete calibration. Pipettors are calibrated overseas by Rainin Company once per year. Calibration certificates are kept in the WAC Quality Assurance Manual. Sampling The laboratory should have a sampling plan and procedure for collecting water samples. The plan should be available at sample locations. Sampling documentation should include sample preparation and at least information on how the sample is collected, the parameters to be tested, date and time of sample collection and the sample collector’s initials. All revisions to sampling procedures should be documented. The WAC Laboratory has incorporated sampling procedures for microbiological and chemical testing into its SOP Manual.
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
Handling of Test and Calibration Items The laboratory must have procedures in place for the transportation, receipt, handling, protection, storage, retention or disposal of test samples. This means that there must be a ‘paper trail’ of documentation to provide information from the time the sample was received in to the laboratory to the time it was disposed (WELAC, 1993). The WAC Laboratory gives a unique identification number to all samples received into the laboratory. The laboratory has a specific SOP created for that purpose which defines how numbers are assigned to each sample. Other SOP’s have been created to document sample storage conditions, methods of preservation and sample retention times. Assuring the Quality of Test Results The laboratory must document all established quality control procedures. It is a requirement of ISO/IEC 17025 that the laboratory participate in a recognised proficiency testing programme to assure the quality of results and where necessary expand/improve on quality control procedures. Statistical quality control charts or equivalent tabulations should be provided for monitoring accuracy and precision performance. The use of reference materials/standards can be used for the monitoring of accuracy performance. Replicate testing of duplicate samples and repeated measurements provides for the monitoring of precision performance. The WAC Laboratory has participated in the Aquacheck WRc (UK) Proficiency Testing programme since June 2000. Statistical quality control charts have been part of our quality assurance programme since the early 1990’s. Reporting the Results The laboratory must report test results accurately, clearly, unambiguously and objectively, and in accordance with specific instructions of the test method. Test reports must include all of the information requested by the customer and necessary for the interpretation of the test. Test reports must have a title, name and address of the laboratory, unique sample ID number, name and address of the customer, identification of the method used, test results and units of measurement, the name, function and signature of the person authorising the test report and an opinion or interpretation of the report where applicable. The WAC Laboratory uses a standardised form called a ‘Laboratory Analysis Report’ for reporting test results. Initially the report did not include information on test methods so we had to revise the report recently to include this. The format of the calibration certificates received by the WAC Laboratory to date has been in accordance with the requirements of the ISO/IEC 17025 test report format. C.
The A2LA Accreditation Process
A laboratory applies for accreditation by obtaining the application package from A2LA headquarters and completing appropriate application sheets (6 in total). All applicants must agree to a set of conditions for accreditation, pay the appropriate fees set by the A2LA Board of Directors, and provide detailed supporting information on: ·
Scope of testing in terms of fields of testing, testing methods and relevant standards. If a laboratory is using its own methods it must provide details on the origin of the
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
method, validation data and a comparison with the standard methods that they replace. · Organisational structure · Proficiency testing Once the application information is completed and the appropriate fees are paid, A2LA staff identifies a suitable assessor to conduct an on-site assessment. Before an assessment is conducted, the assessor requests copies of the quality manual and related documentation (i.e., SOP’s related to ISO/IEC 17025) in order to prepare for the assessment. Prior to scheduling the full assessment, the assessor reviews the draft scope to determine the tests to possibly witness, and checks on the availability of technical personnel who perform the tests. (A2LA, 2000). The assessor provides an assessment agenda. The full assessment generally involves: ·
An entry briefing with laboratory management
·
Interviews with technical staff
·
Demonstration of selected tests
·
Examination of equipment and calibration records
·
Audit of the quality system to verify that it is fully operational and that it conforms to all sections of ISO/IEC 17025, including documentation
·
A written report of the assessor’s findings
·
An exit briefing including the specific written identification of any deficiencies
A2LA take about six weeks to process an application once it has been submitted to their headquarters. During this period the assessor requests the appropriate documentation from the laboratory and once it has been viewed to be complete the assessor schedules an appointment to visit the laboratory concerned and make the final assessment. In some cases laboratories like to have a pre-audit done by A2LA before the final assessment. Although this adds to the final cost it is worthwhile if only to ‘iron out’ any compliance issues before the final assessment. A summary of the A2LA accreditation process is outlined in the flowchart in Figure 1.
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
Figure 1. Flowchart of the A2LA Accreditation Process Adapted from A2LA General Requirements for Accreditation (2000)
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
D.
WAC Laboratory - Progress Towards Accreditation
Accreditation Timeline It was not a sudden decision for the WAC Laboratory to strive for accreditation. It was a rather slow process, which because of workload and staff constraints really only became a reality in 1998. This is when the laboratory first selected how it was going to be accredited. It was decided that the laboratory would seek accreditation in a limited number of drinking water parameters i.e. Total and Faecal Coliform, Heterotrophic Plate Count, pH, Total Dissolved Solids (TDS), Conductivity (EC), pH, Total Chlorine and Free Chlorine. Since drinking water is the most important commodity sold by the WAC it was therefore important to select the parameters for accreditation that best fitted the Authority’s monitoring needs. From a practical point of view it was also known that the accreditation process was not easy and therefore it was crucial for the WAC Laboratory to take its time. Most of 1999 was spent documenting SOP’s and working on the Quality Manual. Small changes in procedures were implemented piece by piece. It was not until the year 2000 that the laboratory made most headway towards accreditation due mainly to the availability of an increased laboratory budget. The WAC Laboratory completed its Quality Manual in February 2001. To date it has compiled twenty-four SOP’s to cover the range of tests for which it is seeking accreditation. At the moment the WAC Laboratory is presently compiling a WAC Compliance Manual for ISO/IEC 17025. This is not a specific requirement of A2LA however it seems to be the best way to ensure that the laboratory covers all of the ISO/IEC 17025 requirements. The Cost of A2LA Accreditation for the WAC Actual costs can vary significantly depending on a laboratory’s size, desired scope of accreditation, and adequacy of its preparation for the assessment. The WAC Laboratory is seeking accreditation in the following limited number of tests: pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Total and Free Chlorine Residual, Total Coliform Bacteria, Faecal Coliform Bacteria and Heterotrophic Plate Count. All of these tests are grouped under the A2LA Environmental Field of Testing. The approximate accreditation cost for the laboratory is summarised in Table 1 below. Table 1 Approximate Cost of Accreditation in US$ for the WAC Laboratory, Grand Cayman (2001). Fee Calculation for 2001
US$
Initial Application Fee for 1 Field of Testing Annual Fee for 1 Field of Testing Assessor Deposit for First Field (estimate)
1,000 1,300 4,000
Total Cost US$ Source: A2LA Fee Schedule, January 1, 2000.
6,300
Proficiency Testing The laboratory enrolled in the Aquacheck (UK) Proficiency Testing Programme for Microbiology and Chemical Testing in June 2000. Apart from being a requirement of 474
The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
ISO/IEC 17025 (1999) to participate in such a programme, WAC management considered this an opportunity to benchmark the laboratory against other laboratories around the world since all participating laboratories in the programme are required to perform the same analysis and submit final results. Proficiency testing adds strength to any quality assurance programme and boosts the confidence and morale of staff. It requires a team effort and promotes continuous improvements in quality control. The laboratory has had good success with the programme so far although it has experienced some difficulties with the transit times involved for the transportation of samples by courier to Grand Cayman. Table 2 illustrates the type of success, which the WAC Laboratory has had with the programme to date, and identifies some areas for improvement. Table 2 WAC Laboratory Percentage Proficiency Testing Results in Compliance with Aquacheck Specified Reference Standards June 2000 – August 2001. Parameter Analysed Total Coliform cfu/100ml Faecal Streptococci cfu/100ml E. Coli cfu/100ml Heterotrophic Plate Count @ 37oC pH (units) in Poorly Buffered Water Magnesium mg/L as CaCO3 Chloride mg/L Sulphate mg/L Conductivity mS/cm
No of tests carried out 42 39 39 6 4 4 4 4 4
WAC Laboratory % Compliant Results 93 72 87 99 100 75 75 50 100
Source: Aquacheck Proficiency Programme Summary of Results 2000-2001. NOTE: All microbiological analysis was performed using the membrane filtration method. Chloride analysis was performed by argentometric titration with AgNO3. Sulphate analysis was performed in accordance with the adapted method of USEPA 375.4 Conductivity analysis was performed with a conductivity meter referenced to 20oC. pH analysis was carried out using an Orion 230A pH meter and triode probe.
The WAC Laboratory is striving to achieve 100% compliance in all of the parameters tested. Presently there are approximately 200 laboratories from around the world participating in the Aquacheck Proficiency Testing Scheme. A2LA requirements are that a laboratory must participate in an A2LA recognised proficiency testing programme at least twice per year and that proficiency testing samples must be related to the laboratory’s scope of accreditation. The Aquacheck scheme complies with both of these requirements. According to A2LA, if a laboratory obtains unacceptable results in two successive rounds of proficiency testing accreditation status for that parameter can be revoked unless the laboratory can supply quality control samples on its own, perform the requisite tests, and report the results of these tests, indicating that it has obtained acceptable results. So far the WAC Laboratory has not had two successive rounds of unacceptable proficiency testing results. The main problem that the WAC laboratory faces at the moment concerns the condition in which the samples are received in Grand Cayman. Samples take approximately three working days to arrive in Grand Cayman via courier from the UK. The samples are usually at room temperature by this
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
stage, which is not a good situation for microbiological analysis since samples must be preserved at 4oC. Aquacheck is working with the WAC Laboratory to improve the situation. Table 2 shows that sulphate analysis results need to be improved. Investigations into the laboratory’s sulphate analysis method has shown us that there is a large variation in the results between one analyst and the next although results on reference standards are good. Further investigation is being done by reviewing the analysis procedures involved. . Pre-Audit Assessment In late 2000 WAC management decided that due to the continuous progress that was made towards accreditation throughout the year it was time to get the laboratory evaluated by an external assessor in order to determine where the laboratory was ‘at’ in terms of achieving accreditation goals. In March 2001, Clancy Environmental Consultants from Vermont performed a pre-audit of the WAC Laboratory at a cost of approximately $5,900. According to the auditor’s report (Clancy, 2001) “the WAC Laboratory team had done an excellent job of preparing for the audit” and overall were considered to be “an excellent group of skilled workers dedicated to quality in their work”. This boosted staff morale and encouraged the laboratory staff to strive even harder for the ultimate goal of accreditation. Of course the laboratory had to improve in certain areas for example, keeping better control of the laboratory’s corrective action procedures or lack thereof, being more consistent in SOP terminology, the establishment of routine pipette calibrations and providing more documentation on dilution water records. Figures 2, 3, 4 and 5 create a ‘picture’ of what the WAC Laboratory looks like today. Like so many other laboratories we started off as ‘humble beginnings’ and developed with time.
Figure 2 Wet Chemistry Area of the WAC Laboratory July 2001.
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
Figure 3 Conductivity and pH Testing Area of the WAC Laboratory, July 2001.
Figure 4 Microbiological Testing Area of the WAC Laboratory July 2001.
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The Road to Laboratory Accreditation using ISO/IEC 17025 – A Cayman Islands Case Study
Fig 5 Fume Hood, Safety Shower and Eye Wash Station Areas of WAC Laboratory, July 2001. In September 2001 the WAC Laboratory submitted an application to A2LA for accreditation. The laboratory is currently waiting for an A2LA assessor to request our quality system documentation and schedule a time for the final audit assessment which it is hoped will be towards the end of November 2001. What is the value of laboratory accreditation? Whom does it benefit? And what are those benefits? There are at least three groups that benefit from laboratory accreditation, the laboratory, users of laboratory services and the general public. (Unger, 2000). The value of laboratory accreditation is that it enables laboratories to develop a standard of service quality that encourages continuous improvement. (Turner, 2000). The main benefits of laboratory accreditation are listed below: · · · · ·
A ‘credential’ that designates the laboratory as qualified to provide services in the fields in which it is credited. A regular, objective ‘check-up’ that helps laboratory management to make continuous improvements in its operation. Improved performance by laboratory staff. Undergoing regular assessments enhances staff discipline and its sense of professionalism. Accreditation assessments help the laboratory staff to stay on the ‘cutting edge’ of technology developments in its field. In the case of A2LA, an international recognition of the accredited laboratory’s competence.
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Conclusions Laboratory accreditation is not ‘rocket science’ but a simple common sense tool for promoting continuous improvement in the management and quality control of the modern laboratory. It must not be viewed as simply a ‘means to an end’ in terms of achieving compliance but a proactive approach to quality management. Laboratory accreditation is achievable by all laboratories both big and small. The key to successful accreditation lies with the dedication and commitment of staff to adopt improved techniques and work standards. For the WAC Laboratory the accreditation process has promoted professionalism among staff and the adoption of better work practices. It has increased productivity and enhanced the quality and reliability of the WAC’s laboratory data. WAC Laboratory staff are committed and dedicated to providing accurate and reliable results in a timely manner. All of the benefits received to date as a result of the laboratory’s participation in the A2LA Accreditation Programme have far outweighed the costs. References A2LA (2000). Applications for Laboratory Accreditation Overview. Document No. 100199. Pg 1. A2LA (2000). A2LA Policy on Measurement Traceability. August 2000. pp 1-9. A2LA (2000). General requirements for Accreditation of Laboratories. August 2000. pp 1-35. Aquacheck WRc (UK) Proficiency Testing Summary of Results 2000-2001. Clancy, J. (2001). Audit report of the Water Authority – Cayman Islands Testing Laboratory. pp 2-9. ISO/IEC 17025 (1999). General Requirements for the Competence of Testing and Calibration laboratories. pp 1-26. Turner, B.G. (2000). Utility Management in the 21st Century – Benefits of Accreditation. AWWA Journal. Vol. 92. No 1., pp 54-55. UKAS (2000). The Expression of Uncertainty in Testing. Edition 1. pp 1-13. Unger, P.S. (2000). President’s Report at A2LA Annual Meeting 2000. Unger, P.S. (2000). An Overview of the Changes to Guide 25. ISO/IEC 17025: The Standard for Laboratory Competence. American Society for Quality Journal. Vol.5.No.10. pp 1-6. Water Authority-Cayman Laboratory SOP Manual (2000). pp 1-72. Water Authority-Cayman Training Log, May 2000. Water Authority-Cayman Quality Assurance Manual 2000. WELAC (1993). Accreditation for Chemical Laboratories. WELAC Guidance Document No. WGD 2. 1993 Edition 1. pp 1-34. Author: Brenda Mac Aree, MSc MCIWEM Water Authority-Cayman P.O. Box 1104GT, Grand Cayman, Cayman Islands Tel: (345) 814-2127 Fax: (345) 949-0094 Email:
[email protected] 479
Innovative Technologies in the Water and Waste Industries in the 21st Century
REGISTERED DELEGATES (as of 25 September 2001)
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Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT Ackbarle
Emil
Adams, Jr.
ORGANISATION Signetix
ADDRESS
E-MAIL
P.O. Bag 458
Point Lisas
Trinidad
[email protected]
E. Lawrence Camp Dresser & McKee Inc.
6365 N.W. 6th Way, Suite 320
Fort Lauderdale, FL 33309
USA
[email protected]
Alessi
Ken
Smith-Blair, Inc
P.O. Box 5337
Texerkara, TX 75505
USA
[email protected]
Alleyne
Kenyatta
C.W.S.A
P.O. Box 1809
Kingstown
St. Vincent
Andrews
W.T.
DesalCo Ltd.
48 Par-La-Ville Rd Suite 381
Hamilton HM 11
Bermuda
Astwood
Lea
Ministry of Works & Utilities
Grand Turk
Awai
Jesse
Tracmac Engineering
Uriah Butler Highway
Chaguanas, P.O. Box 945, Port of Spain
Trinidad
[email protected]
Baggerly
Preston
LifeSource Engineering, Inc.
P.O. Box 3153
Seminole, FL 33775-3153
USA
[email protected]
Baloeo
Sam
Century Eslon Ltd.
1 Century Drive, Trincity
P.O. Box 808 Port of Spain
Trinidad
Banks
Burnstein
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Barendsen
Rin
DesalCo (Barbados) Ltd.
P.O. Box 3087 S
Sr. James P.O.
Barbados
[email protected]
Barnes
Sandy
Barnes Industrial
217Hobbsst Suit 107
Tampa, Fl 33619
USA
rickbarnes46@hotmail,com
Barnes
Rick
Barnes Industrial
217Hobbsst Suit 107
Tampa, Fl 33619
USA
rickbarnes46@hotmail,com
Baynes
Ian
S.I.R Water Management Ltd. Bloomsbury
St Thomas
Barbados
[email protected]
Beach
Valerie
Central Water and Sewerage Authority
P.O Box 363
Kingstown
St. Vincent
[email protected]
Belshaw
Doug
Solinst
35 Todd Rd.
Georgetown, ON L7G 4R8
Canada
[email protected]
Belshaw
Jean
Solinst
35 Todd Rd.
Georgetown, ON L7G 4R8
Canada
[email protected]
Bender
Scott
Shannon & Wilson Inc.
400 N 34th St. Suite 100
Seattle, Washington 98103
USA
[email protected]
Bennett
Doc
Cues
3600 Rio Vista Ave.
Orlando, FL 32805
USA
[email protected]
Bergstrom
Debi
Caribbean Utilities Company
P.O. Box 38 GT
Grand Cayman
Cayman Islands
[email protected]
Bergstrom
Robert A.
Seven Seas Water Corp.
6200 Frydenhoj Suite 4
St. Thomas VI 00802
US Virgin Islands
Bisson
Robert
Earthwater Technology International
206 S. Lee Street
Alexendria, VA
USA
Bodden
John
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Bowman
Christine
Earthwater Technology Trinidad and Tobago LLC
20 Woodlands Rd., Valsayn North
Bradshaw
John
Antigua Public Utilities Authority
P.O Box 416
Brown
Timothy
Heath Consultants Inc.
9030 Monroe Rd.
[email protected]
Turks & Caicos Islands
481
[email protected]
Trinidad
[email protected]
Cassada Gardens, St. Johns
Antigua
[email protected]
Houston TX 77061
USA
[email protected]
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION
ADDRESS
E-MAIL
Brunot
Benoit
Vinci Environment
1, Cours Ferdinand de Lesseps
92851 Rueil Malmaison
France
[email protected]
Burton
Jane
Bio-Service International
1849 25th Street
Vero Beach, Fl 32960
USA
[email protected]
Callahan
Neil V.
R.W. Beck Inc.
PO Box 9344
Framingham, MA 01701-9344
USA
[email protected]
Carter
Sophia
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Carter
Roydell
Environmental Health Department
P.O. Box 1820 GT
Grand Cayman
Cayman Islands
[email protected]
Castillo
Abel
Consilidated Water Company
P.O. Box 1114 GT
Grand Cayman
Cayman Islands
Chacho
Lilia
Thames Water Puerto Rico, Inc.
P.O. Box 373
Sabana Hoyos, PR 00688-0373 Puerto Rico
[email protected]
Charles
Carlye
Lennox Petroleum Services Limited
21 Princess Margaret Street
San Fernando
Trinidad
[email protected]
Clancy
Jennifer L.
Clancy Environmental Consultants
PO Box 314
St. Albans, VT 05478
USA
[email protected]
Clarke
Ken
7636 N. Ingram, Suite 104
Fresno,CA 93711
USA
[email protected]
Collins
Ronald
JCM Industries Inc.
P.O.Box 1220 Nashville
TX 75569
USA
[email protected]
Coppet
Eric
SEEN
ZI La Lezarde
97232 Lamentin
Martinique
[email protected]
Cosley
Dennis
A.Y. McDonald
4800 Chavenlle Rd.
Dubuque, IA 52002
USA
[email protected]
Cosley
Mary
A.Y. McDonald
4800 Chavenlle Rd.
Dubuque, IA 52002
USA
[email protected]
Crabb
Catherine
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Crane
James E.
Camp Dresser & McKee Inc.
6365 N.W. 6th Way, Suite 320
Fort Lauderdale, FL 33309
USA
[email protected]
Crittenden
Prof. Barry
Department of Chemical Claverton Down Engineering, University of Bath
Bath, BA2 7AY
UK
[email protected]
Crowley
Kenneth
DesalCo Ltd.
48 Par-La-Ville #381
Hamilton HM 11
Bermuda
Cummings
Daniel
Central Water and Sewage Authority
P.O. Box 363
Kingstown
St. Vincent
[email protected]
de Verteuil
Laurent
10c Golf Course Rd.
Fairways, Maraval
Trinidad
[email protected]
Denmon
Felix
Southern Sewer Equipment Sales
3409 Industrial 27th St.
Ft. Pierce, Florida 34946
USA
[email protected]
Dookie
Michael
Signetix
P.O. Bag 458
Point Lisas
Trinidad
[email protected]
Duberry
Emile
Montserrat Water Authority
P.O. Box 324
Davy Hill
Montserrat
[email protected]
DumasHarewood
Sherry Ann
University of the West Indies
University of the West Indies
St. Augustine
Trinidad
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REGISTERED DELEGATES REGISTRANT
ORGANISATION
ADDRESS
E-MAIL
Ebanks
Michelle
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Eden
Andrew
Aqua Design Ltd.
P.O. Box 119 SAV
Grand Cayman
Cayman Islands
Edwards
Teddy
Ionics, Incorporated
65 Grove Street
Watertown, MA 02472
USA
Eyzaguirre
Angiecarla
Motorolla Inc.
8000 W. Sunrise Blvd.
Ft Lauderdale, FL 33322
USA
[email protected]
Fisher
Ralph
Fisher Pryce and Associates
26 Haining Rd.
Kingston 5
Jamaica
[email protected]
Foster
Maria
Waste Water Solutions International, Inc.
3238 Old Fence Rd.
Ellicott City, MD 21042
USA
[email protected]
Foster
Tom
WWSI
3238 Old Fence Rd.
Ellicott City, MD 210442
USA
[email protected]
Foxley
Helen
Trouvay & Cauvin S.A. France 58, Rue General-Chanzy
76097 Le Havre
France
Frederick-van Genderen
Gelia
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Fricke
Gary
Heath Consultants Inc.
2085 Piper Lane
London ON N5V 3S5
Canada
Gadsby
Joseph
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Galbraith
Peter
Reid Crowther International
No. 13 Block "C" The Garrison
St. Michael
Barbados
[email protected]
Galbraith
Cheryl
Reid Crowther International
No. 13 Block "C" The Garrison
St. Michael
Barbados
[email protected]
Garbutt
Chris
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Gibson
Cyprian A.
Water and Sewage Corp.
87 Thompson Blvd
Box N3905, Nassau
Bahamas
Glidden
Gloria
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Glidden
Sean
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Grayson
Patrick
ABB Kent Meters Inc.
P.O. Box 225, Isabela
Puerto Rico 00662
Puerto Rico
Grimes
Errol
Water and Sewage Authority
Farm Rd.
St. Joseph
Trinidad
Gulizia
Lynne
Toray Membrane America
3525 Del Mar Heights Rd.
PMB 463 San Diego, CA 92130 USA
[email protected]
Hargy
Thomas
Clancy Environmental Consultants
P.O. Box 314
St. Albans, VT 05478
USA
[email protected]
Hicks
Doug L.
U.S . Filter Distribution
1101W 17th St.
Riviera Beach, FL 33404
USA
[email protected]
Hill
Thomas
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Hoag Jr.
Roland
Earthwater Technology Trinidad and Tobago LLC
20 Woodlands Rd., Valsayn North
Hodge
Vanroy
Anguilla Water Authority
Crocus Hill, P.O. Box 60
The Valley
483
[email protected]
[email protected]
[email protected]
Trinidad
[email protected]
Anguilla
[email protected]
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION
Hoekinas
Rob
Talbot
Hotchkies
James E.
Hughes
ADDRESS
E-MAIL
Winchester S023 OLL
UK
[email protected]
Zenon Environmental Services 3239 Dundas St. W
Oakville, ON L6M4B2
Canada
[email protected]
Joanne
Raven Lining Systems
1024 N. Lansing Ave.
Tulsa, OK 74106
USA
[email protected]
Hunte
Rory D.
PDT Investments Inc.
Cottage Plantation, Cottage
St. Georges
Barbados
[email protected]
Hunter
E.G.
National Water Commission
#14-16 Trinidad Terrace
Kingston 5
Jamaica
Hutchinson
Andrew P.
Associated Consulting Engineers Ltd.
Winslow House, Black Rock
St. Michael
Barbados
[email protected]
Ingari
Joseph
P.O. Box 609,26 Winter Street
Ashland NH 03217
USA
[email protected]
Jacobsen
Carlo
Flonidan Gas Division A/S
Islandsvej 29
8700 Horsens
Denmark
[email protected]
Jadoo
Laerie
Water & Sewerage Authority
Farm Rd.
St Joseph
Trinidad
Jailal
Winston
Century Eslon Ltd.
1 Century Drive, Trincity P.O.Box Port-of-Spain 808
Trinidad
[email protected]
James
Marie
Office of Utilities Regulation
3rd Floor PCJ Resource Centre
36 Trafalgar Rd., Kingston 10
Jamaica
[email protected]
Johnson
Antoinette
Dept. of Environmental Health P.O. Box 1820 GT
Grand Cayman
Cayman Islands
[email protected]
Johnson
Lyle
Spectrum Laboratories Inc.
Ft. Lauderdale, FL 33309
USA
[email protected]
Jones
Dr. Brian
Dept of Earth and Atmospheric University of Alberta Sciences
Edmonton, Alberta T6G 2E3
Canada
[email protected]
Jowett
Robin
Waterloo Biofilter Systems Inc. 143 Dennis Street
P.O. Box 400 Rockwood, Ontario, N0B 2K0
Canada
[email protected]
Jowett
Craig
Waterloo Biofilter Systems Inc. 143 Dennis Street
P.O. Box 400 Rockwood, Ontario, N0B 2K0
Canada
[email protected]
Karallus
Janet
Argo American
4610 Hiatus Rd.
Sunrise, FL 33351
USA
[email protected]
Karallus
Argo
Argo American
4610 Hiatus Rd.
Sunrise, FL 33351
USA
[email protected]
Kuczynski
Teresa
Dept. of Environmental Health P.O. Box 1820 GT
Grand Cayman
Cayman Islands
[email protected]
Lanotti
Frank
Cues
3600 Rio Vista Ave.
Orlando, FL 32805
USA
Lasserre
Jean-Claude Saint Gobain PAM/PAM Colombia
Carrerra 13 A No 89-38 Officina 314
Edif. Nippon Center, Santafe de Colombia Bogata
Lawson
Leo
10 Holborn Rd.
Kingston 10
LeSage
Darell
Vac-Con
969 Hall Park Drive
Green Cove Springs, FL 32068 USA
Leverett
Billy
Ocean Conversion (BVI) Ltd.
P.O. Box 122
Road Town, Tortola
Lawson & Assocs -Consul. Engs.
Winnall Valley Rd.
1460 W. McNab Rd.
484
Jamaica
BVI
[email protected]
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION
ADDRESS
E-MAIL
Lewis
O' Reilly
Central Water & Sewerage Authority
P.O. Box 363
Kingstown
St. Vincent
[email protected]
Lightbourne
Kenneth
Waterfields
P.O. Box CR 54030
Nassau
Bahamas
[email protected]
Lindeman
Don
Tampa Bay Water
2535 Landmark Drive, Suite 211 Clearwater, FL 33761
USA
[email protected]
Lines
Alan
Dyka Plastic Pipe Systems
65-69 Ellingham Way,
Ashford, Kent TN23 6JU
UK
[email protected]
Little
Dee
Aqua Smart Inc.
4445 Commerce Dr., Suite A-4
Atlanta, GA 30336
USA
[email protected];
Little
Lyle
Aqua Smart Inc.
4445 Commerce Dr., Suite A-4
Atlanta, GA 30336
USA
[email protected];
Lloyd
Barry.
Centre of Environmental Health Engineering
Dept. of Civil Engineering, University of Surrey, Guildford GU25XH
UK
[email protected]
Lopes
Antonio
ZI La Lezarde
97232 Lamentin
Martinique
[email protected]
Lorenzo
Pedro
P.O. Box 13455
San Juan PR 00908
Puerto Rico
[email protected]
Ludvigsen
Kim
A.V.K. Overseas
7636 N. Ingram Suite 104, 7637
Fresno CA 93711
USA
[email protected]
Lytle
Tom
Vermeer Caribbean Sales & Service
6970 Wallis Rd. Suite 1C
West Palm Beach, FL 33413
USA
[email protected]
Lytle
Pam
Vermeer Caribbean Sales & Service
6970 Wallis Rd. Suite 1C
West Palm Beach, FL 33413
USA
[email protected]
Mac Aree
Brenda
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Magee
John
Motorolla Inc.
8000 W. Sunrise Blvd.
Ft Lauderdale, FL 33322
USA
Maharaj
Utam
Water & Sewerage Authority
c/o WASA, Farm Rd.
St. Joseph
Trinidad
Makky
Julius
Foremost Industries
1225-64 Avenue NE
Calgary AB, T2E89P
Canada
[email protected]
Malpass
Greg
Biwater International
Dorking,
Surrey RH4 ITZ
UK
[email protected]
Mara
Duncan
School of Civil Engineering
University of Leeds
Leeds LS2 9JT
UK
[email protected]
Marino
Frank
Semsco International
140 Commerce Rd., Boynton Beach
FL 33426
USA
MartinezEbanks
Marcela
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Mc Callum
George
GDM Lindex Ltd.
The Courtyard Long Row
Newark, Notts., NG24 112W
UK
[email protected]
Mc Callum
Hamish
GDM Lindex Ltd.
The Courtyard Long Row
Newark, Notts., NG24 112W
UK
[email protected]
McCorquodale
Donald
Spectrum Laboratories Inc.
1460 W McNab Rd.
Ft. Lauderdale, FL 33309
USA
[email protected]
..University Of Surrey
SEEN
485
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION
ADDRESS
E-MAIL
McCoullough
Robert
Dept. of Environmental Health P.O. Box 1820 GT
Grand Cayman
Cayman Islands
[email protected]
McKinney
Jerry
Clearstream Wastewater Systems
PO Box 7568
Beaumont, TX 77726-6500
USA
McLaughlin Cuzzi
Martie
Ionics, Incorporated
65 Grove St.
Watertown, MA. 02472
USA
McTaggart
Frederick
Consolidated Water Company PO Box 1114 GT
Grand Cayman
Cayman Islands
[email protected]
McTaggart
Greg
Consolidated Water Company PO Box 1114 GT
Grand Cayman
Cayman Islands
Ft Lauderdale, FL 33322
USA
[email protected]
Mederos
Milton
Motorolla Inc.
8000 W. Sunrise Blvd.
Meekings
Helen
Dept. for International Development (Montserrat)
Manjack
Melendez
William
Ramar
P.O. Box 110127,Research Triangle Park
NC 27709-0127
Mercado
Victor
Thames Water Puerto Rico, Inc.
P.O. Box 373
Sabana Hoyos, PR00688-0373 Puerto Rico
[email protected]
Merideth
David
ABB Water Meters Inc.
P.O. Box 225 Isabela
Puerto Rico 00662
Puerto Rico
[email protected]
Morgan
Kenneth C.
KCM Consulting Services, Inc. 4723 Chandler Services, Inc.
Denver, CO 80239
USA
[email protected]
Morris
Jim
Clearstream Wastewater Systems
P.O. Box 7568
Beaumont, TX 77726-7568
USA
[email protected]
Nance
Stewart
Raven Lining Systems
1024 N. Lansing Ave.
Tulsa, OK 74106
USA
[email protected]
Nicholson
Robert
Sea Solar Power International 1115 Calvert St. Suite 2300
Baltimore, MD 21202-6174
USA
[email protected]
Noel
Jean-Mark
Trouvay & Cauvin S.A. France 58, Rue General-Chanzy
76097 Le Havre
France
Nunes
Joseph
Equipment & Supply (W.I.) Limited
Lady Hailes Avenue
San Fernando
Trinidad
[email protected]
Oudit
Lennox
Process Components Ltd.
#17-19 Maharaj Avenue
Marabella
Trinidad
[email protected]
Paul
Lydia
Signetix
P.O. Bag 458
POINT LISAS
Trinidad
[email protected]
Pepe
Frank J.
Bio-Service International
P.O. Box 1773
Hope Sound, FL 33425
USA
Pereira
Gerard
Ocean Conversion Ltd.
P.O. Box 30614 SMB
Grand Cayman
Cayman Islands
[email protected]
Persad
Lennox
1st Avenue South
Western Main Rd San Fernando
Trinidad
[email protected]
Philippeaux
Harry
Dayrall Rd., P.O. Box 508
Bridgetown
Barbados
[email protected]
PAHO-Barbados
486
Montserrat
[email protected]
USA
[email protected]
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION ESRI
ADDRESS
Pittman
Adam
Ramjeet
Jerrybandan Ocean Conversion Ltd.
Ramrattan
Bill
Trinidad and Tobago Solid 34 Independence Square Waste Management Company Limited
Ramroop
Clement
Redhead
Judith
E-MAIL
380 New York Street
Redlands, CA 92373-8100
USA
[email protected]
P.O. Box 30614 SMB
Grand Cayman
Cayman Islands
[email protected]
Port of Spain
Trinidad
[email protected]
Trinidad and Tobago Solid 34 Independence Square Waste Management Company Ltd.
Port of Spain
Trinidad
[email protected]
S.I.R. Water Management Ltd. Bloomsbury
St. Thomas
Barbados
[email protected]
Cayman Islands
[email protected]
Reid
Antoney
CMEC, LTD
P.O. Box 10589 APO
Grand Cayman
Rijmers
Peter
Dyka Plastic Pipe Systems
Deccaweg 25
1042 AE Amsterdam
Holland
Robinson
Stacy
Ministry of Works & Utilities
Grand Turk
Turks & Caicos Islands
Rojanskiy
Henrikk
IDE Technologies, Ltd.
13 Zarchin Rd.
P.O. Box 591 Raanana, 43104
Israel
Rudolph, PhD
John
Clemson University
Wastewater Engineering Dept. Clemson University
Clemson SC
USA
[email protected]
Sankar
Randolph
Water & Sewerage Authority
c/o WASA, Farm Rd
St. Joseph
Trinidad
[email protected]
Santha
Brent
Consolidated Water Company P.O. Box 1114 GT
Grand Cayman
Cayman Islands
Satney
Martin
General Manager Water & Sewage Authority
P.O. Box RB2310
Gros Islet
St. Lucia
[email protected]
Sealy
Hugh
Stantec Consulting International Inc.
Warrens Great House
Warrens, St. Micheal
Barbados
[email protected]
Sherman
Godfrey
Water and Sewage Corp.
P.O. Box N-3905
Nassau
Bahamas
[email protected]
Siung-Chang, PhD
Avril
Pan American Health Organization
P.O. Box 898
Port-of-Spain
Trinidad
[email protected]
Smith
Bob
Caribbean Utilities Company
P.O. Box 38 GT
Grand Cayman
Cayman Islands
[email protected]
Smith
Henry
University of the Virgin Islands #2 John Brewers Bay SFC Room 204
St. Thomas VI 00802-9990
US Virgin Islands
[email protected]
Smith
George M.
U.S . Filter Distribution
1101W 17th St.
Riviera Beach, FL 33404
USA
[email protected]
Stalford
Richard
RNS Consulting
121 Wellington Drive
Matthews, NC 28104
USA
[email protected]
Meyer-Steele
Shawn
Ionics, Incorporated
65 Grove Street
Watertown, MA 02472
USA
[email protected]
Stephens
Marian
CWWA Secretariat
C/O WASA
Farm Rd.,St Joseph
Trinidad
[email protected]
487
Innovative Technologies in the Water and Waste Industries for the 21st Century
REGISTERED DELEGATES REGISTRANT
ORGANISATION
ADDRESS
E-MAIL
Sullivan
Lori
ESRI
380 New York Street
Redlands CA 92373-8100
USA
[email protected]
Sweeney
Vincent
Caribbean Environmental Health Inst
P.O.Box 1111
Castries
St. Lucia
[email protected]
Tedd
Martin
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Telliard
William
US Enviromental Protection Agency
Engineering and Analysis Division (4303)
1200 Pennsylvania Avenue, Washington DC 20460
USA
[email protected]
Thompson
Ed
J.C.M. Industries Inc
P.O. Box 1220, Nashville
TX 75569-1220
USA
[email protected]
Tota-Maharaj
Tawarie
Water &Sewerage AuthorityTrinidad
c/o WASA Farm Rd.
St. Joseph
Trinidad
Trippensee
Fred
Trippensee & Co.
4906 Us Highway 27, S
Sebring, FL 33870
USA
van Genderen
Hendrik
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
van Zanten
Tom
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Vicente Paganacci Wallace
Manuel
Ineco International
P.O. Box 29006
San Juan, 00929
Puerto Rico
Jerome
Caribbean Utilities Company
P.O. Box 38 GT
Grand Cayman
Cayman Islands
[email protected]
Warren
Wendy
Water Authority-Cayman
P.O. Box 1104 GT
Grand Cayman
Cayman Islands
[email protected]
Watler
David
Caribbean Utilities Company
P.O. Box 38 GT
Grand Cayman
Cayman Islands
[email protected]
Watson
Clement
National Water Commission
24-48 Barbados Avenue
Kingston 5
Jamaica
[email protected]
Watts
Michelle
Water Resources Authority
Hope Gardens, P.O. Box 91
Kingston 7
Jamaica
[email protected]
Whittaker
Troy
Entech Engineering
P.O. Box 11561 APO
Grand Cayman
Cayman Islands
[email protected]
Woolley
Derek
DesalCo. Ltd.
48 Par-la-Ville Rd. #381
Hamilton HM 1
Bermuda
[email protected]
Whyte
Noel O.
N.O. Whyte & Assoc.
Suite 13 Montego Freeport Shopping Centre
Montego Bay
Jamaica
[email protected]
Williams
Andrea
Central Water and Sewerage Authority
P.O Box 363
Kingstown
St. Vincent
[email protected]
Williams
David J.
Century Eslon Ltd.
1 Century Drive, Trincity
P.O. Box 808 Port of Spain
Trinidad
Williams-Lewis
L. Andrea
Central Water and Sewarage Authority
P.O. Box 363
Kingstown
St. Vincent
488
[email protected]
[email protected]
[email protected]
Innovative Technologies in the Water and Waste Industries in the 21st Century
EXHIBITORS
489
Innovative Technologies in the Water and Waste Industries in the 21st Century
EXHIBITIORS A.Y. McDonald Mfg. Co. P.O. Box 508 Dubuque IA 52004-0508 USA Tel: 1-800-292-2737 Fax: 1-800-832-9296
[email protected] www.aymcdonald.com
Consolidated Water Company Ltd. P.O. Box 1114 GT Cayman Islands Tel: 345-945-4277 Fax: 345-945-4191
[email protected] www.consolidated-water.com Cues 3600 Rio Vista Ave Orlando FL 32805 USA Tel: 407-849-0190 or 1-800-327-7791 Fax: 407-425-1569 www.cuesinc.com
ABB Water Meters Inc. PO Box 225 Isabella PR 00662 Puerto Rico Tel: 787-872-2515 Fax: 787-872-2006 www.abb.com
Desalco Ltd. 48 Par-la-Ville Rd #381 Hamilton HM11 Bermuda Tel: 441-292-2060 Fax: 441-292-2024 www.desalco.bm
Aqua Smart Inc. 4445 Commerce Dr. Suite A-4 ATLANTA GA 30336 USA Tel: 404-696-4406 Fax: 404-696-3712
[email protected] www.aquasmartinc.com
Entech Ltd. PO Box 812 GT Cayman Islands Tel: 345-947-9253 Fax: 345-947-7407
[email protected]
AVK Overseas 7636 N. Ingram, Suite 104 Fresno CA 93711 USA Tel: 559-451-0435 Fax: 559-451-0437
[email protected] www.avk.dk
ESRI 380 New York Street Redlands CA 92373-8100 USA Tel: 909-793-2853 ext. 11329 Fax: 909-307-3072 www.esri.com
Clearstream Wastewater Systems Inc. P.O. Box 7568 Beaumont Texas 77726-7568 USA Tel: 409-755-1500 Fax: 409-755-6500 www.clearstreamsystems.com
Florida Aquastore 4722 NW Boca Raton Blvd., Suite C-102 Boca Raton FL 33431 USA Tel: 561-994-2400 Fax: 561-994-2444
[email protected]
490
Innovative Technologies in the Water and Waste Industries in the 21st Century
EXHIBITIORS Foremost Industries Inc. 1225-64 Avenue N.E. Calgary Alberta T2E 8P9 Canada Tel: 403-295-5841 Fax: 403-295-5834
[email protected] http://www.foremost.ca/
Raven Lining Systems 1024 N. Lansing Avenue Tulsa OK 74106 USA Tel: 918-584-2810 Fax: 918-582-4311
[email protected] www.ravenlining.com Saint-Gobain/Pont a Mousson Colombia S.A. Carrera 13 A No. 89-38 Oficina 314 Edif. Nippon Center Santafe de Bogata Colombia Tel: 571-618-2814 Fax: 571-618-2502 www.sg-canalizacion.com.co
GDM Lindex Ltd. The Courtyard Long Row Newark, Notts UK Tel: 44-1636-610030 Fax: 44-1636-610022
[email protected] www.gdmlindex.com
SEEN ZI la Lezarde 97232 Lamentin Martinique - French West Indies Tel: 596-666601 Fax: 596-516125 www.seen-martinique.com
International Desalination Association P.O. Box 387 Topsfield MA 01983 USA Tel: 978-887-0410 Fax: 978-887-0411 www.ida.com
SEMSCO International 140 Commerce Road Boynton Beach FL 33426 USA Tel: 561-547-3133 Fax: 561-547-3134 www.claytonsupply.com
Ionics Inc. 65 Grove Street Watertown MA 02472 USA Tel: 617-926-2500 Fax: 617-926-4304
[email protected] www.ionics.com
Signetix/Motorolla Atlantic Avenue Point Lisas P.O. Bag 458 California Trinidad Tel: 868-636-8264/5 or 954-723-5827 Fax: 868-636-8262
[email protected] www.motorola.com www.nemal-and-massy.co
JCM Industries Inc. P.O. Box 1220 Nashville TX 75569 USA Tel: 903-832-2581 Fax: 903-838-6260 www.jcmind.com
Smith Blair Inc. P.O. Box 5337 Texarkana TX 75505 USA Tel: 870-773-5116 Fax: 870-773-5118 www.smith-blair.com
Ocean Conversion Cayman Ltd. PO Box 30614 SMB Cayman Islands Tel: 345-945-5106 Fax: 345-945-5105 www.desalco.bm
491
Innovative Technologies in the Water and Waste Industries in the 21st Century
EXHIBITIORS Solinst Canada Ltd. 35 Todd Road Georgetown ON L7G 4R8 Canada Tel: 905-873-2255 Fax: 905-873-1992 www.solinst.com
Waterloo Biofilter Systems Inc. 143 Dennis Street Rockwood ON NOB 2KO Canada Tel: 519-856-0757 Fax: 519-856-0759
[email protected] www.waterloo-biofilter.com
Trouvay & Cauvin Agence Antilles 58 Rue General-Chanzy 76097 Le Havre Cedex 7004 X France Tel: 33-590-267-146 or 33-590-908-272 Fax: 33-590-266-047 www.trouvay-cauvin.fr
Zenon Environmental 3239 Dundas Street West Oakville Ontario L6M 4B2 Canada Tel: 905-465-3030 ext 3266 Fax: 905-465-3050 www.zenonenv.com
US Filter Corporation 1101 W 17th Street Riviera Beach FL 33404 USA Tel: 561-848-4396 Fax: 561-848-3169 www.usfilter.com VacCon - Southern Sewer Equipment 3409 Industrial 27th St Ft Pierce FL 34946 USA Tel: 561-595-6940 Fax: 561-595-9171
[email protected] www.southernsewer.com www.vac-con.com Vermeer Caribbean 6970 Wallis Rd #1c West Palm Beach FL 33413 USA Tel: 561-478-1114 Fax: 561-478-7955 www.vermeer.com Wastewater Solutions International Inc. 3238 Old Fence Road Ellicott City MD 21042 USA Tel: 410-480-0272 Fax: 410-480-0282
[email protected]
492
