WPS5412 Policy Research Working Paper 5412 Public Disclosure Authorized Improving Wastewater Use in Agriculture An Emerging Priority Public Disclosure Authorized Susanne M. Scheierling Carl Bartone Duncan D. Mara Pay Drechsel Public Disclosure Authorized The World Bank Public Disclosure Authorized Water Anchor Energy, Transport, and Water Department September 2010 Policy Research Working Paper 5412 Abstract Wastewater use in agriculture is a growing practice to different aspects of wastewater irrigation to a country’s worldwide. Drivers include increasing water stress, in level of economic development. Based on data presented part due to climate change; increasing urbanization and in the World Bank’s World Development Report, it growing wastewater flows; and more urban households differentiates between four country income levels to engaged in agricultural activities. The problem with create a typology for analyzing current issues, trends, this trend is that in low-income countries, but also in and priorities for improving agricultural wastewater use many middle-income countries, it either involves the with a focus on reducing the risks to public health. It direct use of untreated wastewater or the indirect use of also presents the basic principles of the new 2006 World polluted waters from rivers that receive untreated urban Health Organization Guidelines, and how to apply them. discharges. This poses substantial risks, in particular Beyond regulatory aspects, the paper also discusses other microbial risks to public health. To address these risks, aspects that are important for achieving a more integrated the World Health Organization in 2006 issued new approach to agricultural wastewater use, including guidelines for the safe use of wastewater. institutional/planning, technological, economic/ This paper aims to highlight the growing importance financial, and social issues. Finally, the paper provides of improving wastewater use in agriculture across the recommendations for moving the wastewater irrigation spectrum from lower to high-income countries. It agenda forward. presents an innovative approach linking key issues related This paper—a product of the Energy, Transport and Water Department, Water Anchor—is part of a larger effort in the department to assess the feasibility of interventions for improving wastewater use in agriculture.. Policy Research Working Papers are also posted on the Web at http://econ.worldbank.org. The author may be contacted at [email protected]. The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent. Produced by the Research Support Team Improving Wastewater Use in Agriculture: An Emerging Priority* Susanne M. Scheierling The World Bank Carl Bartone Consultant Duncan D. Mara University of Leeds, UK Pay Drechsel International Water Management Institute (IWMI) The World Bank Water Anchor Energy, Transport, and Water Department August 2010 * Contact information: [email protected]. We are grateful to following colleagues at the World Bank for helpful comments and guidance during the discussion of the concept note, the presentation of initial study results, and the review meeting: Mohammed Benouahi, Marjory-Anne Bromhead, Julia Bucknall, Alexander Danilenko, Daniel Hoornweg, Peter Kolsky, Paul Kriss, Abel Mejia, and Halla Qaddumi. The authors also wish to acknowledge constructive comments from the peer reviewers Alexander Bakalian, Menahem Libhaber, and Jamie Bartram (University of North Carolina at Chapel Hill), Further comments were received from Blanca Jimenez (Universidad Nacional Autónoma de México, UNAM), Mark Redwood (International Development Research Centre, IDRC), and Takashi Asano (University of California at Davis). Alexandra Evans (International Water Management Institute, IWMI) contributed to the materials on urban agriculture, and Bénédicte Augeard (World Bank) to the portfolio review. The paper received financial support through the Water Partnership Program (WPP). It is based on Economic and Sector Work carried out in the Water Anchor, Energy, Transport and Water Department. A more detailed report is available at http://siteresources.worldbank.org/INTWAT/Resources/ESWWastewaterAg.pdf. Contents Chapter 1. Introduction ................................................................................................................... 1 Chapter 2. Issues and Trends in Wastewater Use in Agriculture ................................................ 3 2.1 Wastewater use in agriculture: past and current practice ........................................................... 3 2.2 Key issues in wastewater use in agriculture ............................................................................... 7 2.3 Powerful drivers toward growing wastewater use in irrigation ............................................... 19 Chapter 3. Risks and Benefits of Wastewater Use in Agriculture ............................................. 22 3.1 Risks to public health ............................................................................................................... 22 3.2 Environmental risks and benefits ............................................................................................. 30 3.3 Agricultural and water resources management benefits .......................................................... 32 3.4 Objectives for improving wastewater irrigation ...................................................................... 32 Chapter 4. Assessing and Managing Microbial Risk to Public Health ..................................... 33 4.1 Risk assessment and management framework of the 2006 WHO Guidelines ......................... 33 4.2 Currently recommended microbial risks assessment and management framework ................ 38 4.3 Options for reducing microbial risks ....................................................................................... 41 4.4 Applying quantitative microbial risk analysis ......................................................................... 43 Chapter 5. Toward an Agenda for Improving Wastewater Use in Agriculture ....................... 46 5.1 Implementing measures for reducing public health risks ........................................................ 46 5.2 Promoting an integrated approach to planned wastewater use for irrigation ........................... 56 Chapter 6. Concluding Remarks .................................................................................................. 75 Annexes Annex A: Quantitative Microbial Risk Analysis: Developments since the2006 WHO Guidelines . 78 Annex B: Verification Monitoring of Pathogen Reductions Achieved by Wastewater Treatment and Health-Protection Control Measures ......................................................................... 90 Annex C: Projects on Wastewater Irrigation Approved in Fiscal Year 1999-2009 .......................... 93 References ......................................................................................................................................... 94 Chapter 1. Introduction Wastewater use is a growing practice worldwide.1 As freshwater sources become scarcer, wastewater use has become an attractive option for conserving and expanding available water supplies. Wastewater use can have many types of applications, including irrigation of agricultural land, aquaculture, landscape irrigation, urban and industrial uses, recreational and environmental uses, and artificial groundwater recharge (Asano et al., 2007). Principally, wastewater can be used for all purposes for which freshwater is used, given appropriate treatment and reliable operation. With a few exceptions worldwide, wastewater use applications are restricted to nonpotable uses, or at most to indirect potable uses. Wastewater use in agriculture is by far the most established application, and the one with the longest tradition. In most cases the irrigated lands are located in or near the urban areas where the wastewater is generated. Estimates on wastewater use worldwide indicate that about 20 million hectares of agricultural land is irrigated with (treated and untreated) wastewater (Jiménez and Asano, 2008). Especially in lower income countries and in arid and semi-arid high-income countries, wastewater irrigation is the most prominent and also the most rapidly expanding wastewater use. Besides increasing water stress, drivers for the expansion include increasing urbanization, growing urban wastewater flows due to the expansion of water supply and sewerage services, and more urban households engaged in agricultural activities that could be intensified with additional sources of irrigation water. The problem with this growing trend toward more agricultural wastewater use is that in low-income countries, but also many middle-income countries, the practice either involves the direct use of untreated wastewater or the indirect use of polluted waters from rivers