Wastewater Irrigation and Health This page intentionally left blank Wastewater Irrigation and Health Assessing and Mitigating Risk in Low-Income Countries Edited by Pay Drechsel, Christopher A. Scott, Liqa Raschid-Sally, Mark Redwood and Akiça Bahri publishing for a sustainable future London • Sterling, VA First published by Earthscan with the International Development Research Centre (IDRC) and the International Water Management Institute (IWMI) in the UK and USA in 2010 Copyright © International Water Management Institute and International Development Research Centre, 2010 All rights reserved ISBN 978-1-84407-795-3 hardback ISBN 978-1-84407-796-0 paperback Typeset by JS Typesetting Ltd, Porthcawl, Mid Glamorgan Cover design by Ruth Bateson For a full list of publications please contact: Earthscan Dunstan House 14a St Cross Street London EC1N 8XA, UK Tel: +44 (0)20 7841 1930 Fax: +44 (0)20 7242 1474 Email: [email protected] Web: www.earthscan.co.uk 22883 Quicksilver Drive, Sterling, VA 20166-2012, USA Earthscan publishes in association with the International Institute for Environment and Development IDRC publishes an e-book edition of this book (ISBN 978-1-55250-475-8) For further information, please contact: International Development Research Centre PO Box 8500 Ottawa, ON Canada K1G 3H9 Email: [email protected] Web: www.idrc.ca IDRC is a Canadian public corporation that works in close collaboration with researchers from the developing world with the aim of building healthier, more equitable and more prosperous societies A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data Wastewater irrigation and health : assessing and mitigating risk in low-income countries / edited by Pay Drechsel … [et al.]. p. ; cm. Includes bibliographical references and index. ISBN 978-1-84407-795-3 (hardback) – ISBN 978-1-84407-796-0 (pbk.) 1. Sewage irrigation–Developing countries. 2. Sewage–Health aspects. 3. Public health–Developing countries. I. Drechsel, Pay. [DNLM: 1. Sewage. 2. Water Purification. 3. Agriculture–methods. 4. Developing Countries. 5. Risk Assessment. WA 690 W323 2009] TD760.W345 2009 363.72’84--dc22 2009029309 At Earthscan we strive to minimize our environmental impacts and carbon footprint through reducing waste, recycling and offsetting our CO2 emissions, including those created through publication of this book. For more details of our environmental policy, see www.earthscan.co.uk. This book was printed in the UK by MPG Books, an ISO 14001 accredited company. The paper used is FSC certified. Contents Figures, Tables and Boxes ix Foreword by Hillel Shuval xv Preface xix Contributors and Reviewers xxi Abbreviations xxv PART 1 — SETTING THE STAGE 1 Wastewater, Sludge and Excreta Use in Developing Countries: An Overview 3 Blanca Jiménez, Pay Drechsel, Doulaye Koné, Akiça Bahri, Liqa Raschid-Sally and Manzoor Qadir 2 Assessing and Mitigating Wastewater-Related Health Risks in Low-Income Countries: An Introduction 29 Robert Bos, Richard Carr and Bernard Keraita PART 2 — RISKS AND RISK ASSESSMENT 3 Risk Analysis and Epidemiology: The 2006 WHO Guidelines for the Safe Use of Wastewater in Agriculture 51 Duncan Mara and Robert Bos 4 Approaches to Evaluate and Develop Health Risk-Based Standards Using Available Data 63 Inés Navarro, Peter Teunis, Christine Moe and Blanca Jiménez 5 Tools for Risk Analysis: Updating the 2006 WHO Guidelines 89 Duncan Mara, Andrew J. Hamilton, Andrew Sleigh, Natalie Karavarsamis and Razak Seidu vi WASTEWATER IRRIGATION AND HEALTH 6 Non-Pathogenic Trade-Offs of Wastewater Irrigation 101 Manzoor Qadir and Christopher A. Scott 7 Risk Analysis Integrating Livelihood and Economic Impacts of Wastewater Irrigation on Health 127 Marites M. Tiongco, Clare A. Narrod and Kelly Bidwell PART 3 — MINIMIZING HEALTH RISKS 8 Wastewater Treatment for Pathogen Removal and Nutrient Conservation: Suitable Systems for Use in Developing Countries 149 Blanca Jiménez, Duncan Mara, Richard Carr and François Brissaud 9 Low-Cost Options for Pathogen Reduction and Nutrient Recovery from Faecal Sludge 171 Doulaye Koné, Olufunke O. Cofie and Kara Nelson 10 Farm-Based Measures for Reducing Microbiological Health Risks for Consumers from Informal Wastewater-Irrigated Agriculture 189 Bernard Keraita, Flemming Konradsen and Pay Drechsel 11 Farm-Based Measures for Reducing Human and Environmental Health Risks from Chemical Constituents in Wastewater 209 Robert Simmons, Manzoor Qadir and Pay Drechsel 12 Applying the Multiple-Barrier Approach for Microbial Risk Reduction in the Post-Harvest Sector of Wastewater-Irrigated Vegetables 239 Sanja Ilic, Pay Drechsel, Philip Amoah and Jeffrey T. LeJeune 13 Cost-Effectiveness Analysis of Interventions for Diarrhoeal Disease Reduction among Consumers of Wastewater-Irrigated Lettuce in Ghana 261 Razak Seidu and Pay Drechsel PART 4 — WASTEWATER GOVERNANCE AND ADOPTION OF RISK-REDUCTION OPTIONS 14 Challenging Conventional Approaches to Managing Wastewater Use in Agriculture 287 Frans Huibers, Mark Redwood and Liqa Raschid-Sally CONTENTS vii 15 Designing Reuse-Oriented Sanitation Infrastructure: The Design for Service Planning Approach 303 Ashley Murray and Chris Buckley 16 Facilitating the Adoption of Food-Safety Interventions in the Street-Food Sector and on Farms 319 Hanna Karg, Pay Drechsel, Philip Amoah and Regina Jeitler 17 Harnessing Farmers’ Knowledge and Perceptions for Health-Risk Reduction in Wastewater-Irrigated Agriculture 337 Bernard Keraita, Pay Drechsel, Razak Seidu, Priyanie Amerasinghe, Olufunke O. Cofie and Flemming Konradsen 18 Multi-Stakeholder Processes for Managing Wastewater Use in Agriculture 355 Alexandra E. V. Evans, Liqa Raschid-Sally and Olufunke O. Cofie PART 5 — CONCLUSIONS AND OUTLOOK 19 Wastewater Irrigation and Health: Challenges and Outlook for Mitigating Risks in Low-Income Countries 381 Christopher A. Scott, Pay Drechsel, Liqa Raschid-Sally, Akiça Bahri, Duncan Mara, Mark Redwood and Blanca Jiménez Index 395 This page intentionally left blank Figures, Tables and Boxes FIGURES 1.1 Freshwater withdrawals for agricultural use in the year 2000 and countries reporting the use of wastewater or polluted water for irrigation 6 1.2 Options to deal with the reuse of wastewater for agricultural purposes 20 2.1 Feasible combinations of farm-based interventions and achievable reduction of thermotolerant coliforms on lettuce leaves in Kumasi, Ghana 42 4.1 Dose-response relation for infection by Norwalk virus in human challenge study 69 4.2 Dose-response relation for E. coli O157:H7 based on eight different outbreaks, using a two-level dose-response model, allowing for variation between outbreaks 69 4.3 Risk estimate from annual exposure to spinach irrigated with four different Ascaris concentrations in wastewater for several consumption rates 79 4.4 Estimated annual risk of Ascaris infection associated with exposure to spinach grown on biosolids-amended soil 80 4.5 Estimated annual risk of Ascaris infection associated with exposure to carrots grown on biosolids-amended soil 80 5.1 Schematic of recommended (Approach A) and not recommended (Approach B) methods for determining annual infection risk 92 6.1 Comparative evaluation of macronutrient concentrations in untreated and treated wastewater from Haryana, India 107 6.2 Organic carbon dynamics in soil as affected by freshwater irrigation and wastewater irrigation for 15 and 25 years in India 109 6.3 Total phosphorous with distance downstream of discharge point, Rio Guanajuato, Mexico, 1998 111 6.4 Electrical conductivity with distance downstream of discharge point, Rio Guanajuato, Mexico, 1998 111 x WASTEWATER IRRIGATION AND HEALTH 6.5 Head–tail water quality, Tula Irrigation District, Mexico, 1997–98 112 7.1 Risk analysis framework 130 7.2 Risk reduction/cost trade-off 134 10.1 One of several dugout ponds farmers are using on informal urban vegetable farms in Kumasi, Ghana 193 10.2 Concrete reservoir used by smallholders in Lomé, Togo 194 10.3 Watering cans with mosquito mesh to avoid debris (Dakar, Senegal) 195 10.4 Weir in the Musi river, downstream of Hyderabad, Andhra Pradesh, India 196 10.5 Farmer standing on a wooden log while fetching water from a small dugout pond (Kumasi, Ghana) 197 10.6 Farmer fetching water with a can on a rope from a wastewater stream (Ouagadougou, Burkina Faso) 197 10.7 Lifting pumps inflow valves out of the sediment of irrigation channels near Hyderabad, India 198 10.8 Simple drip irrigation kit made in India and tested in Ghana for lettuce 199 10.9 Holding the watering can at low height and using an outflow rose reduces splashing of already contaminated soil on the crop (Kumasi, Ghana) 200 12.1 Multiple-barrier approach in the wastewater food chain where treatment alone is an insufficient pathogen barrier 242 12.2 Types of disinfectants used according to the category of restaurants in Cotonou, Benin 251 13.1 Projected distribution of wastewater-irrigated lettuce consumer population in urban Ghana 266 13.2 DALYs averted by interventions 274 13.3 Expansion path showing dominated interventions 276 14.1 The water chain: conceptual framework showing upstream- downstream links 290 15.1 Schematic of Design for Service (DFS) sewage treatment planning framework and corresponding methods 310 16.1 Description of the four Ps when used in social marketing 324 16.2 Suggested multi-strategy campaign framework for the adoption of non-treatment interventions, on farm and off farm, for the reduction of health risks due to wastewater irrigation in urban