WORKING PAPER 37 Wastewater Use in Agriculture Review of Impacts and Methodological Issues in Valuing Impacts Postal Address P O Box 2075 Colombo Sri Lanka Intizar Hussain, Liqa Raschid, Munir A. Hanjra, Location 127, Sunil Mawatha Fuard Marikar and Wim van der Hoek Pelawatta Battaramulla Sri Lanka Telephone 94-1-787404, 784080 Fax 94-1-786854 E-mail [email protected] Website www.iwmi.org SM SM International International Water Management Water Management IWMI is a Future Harvest Center Institute supported by the CGIAR Institute Working Paper 37 WASTEWATER USE IN AGRICULTURE: REVIEW OF IMPACTS AND METHODOLOGICAL ISSUES IN VALUING IMPACTS [With an Extended List of Bibliographical References] Intizar Hussain Liqa Raschid Munir A. Hanjra Fuard Marikar and Wim van der Hoek International Water Management Institute i IWMI receives its principal funding from 58 governments, private foundations, and international and regional organizations known as the Consultative Group on International Agricultural Research (CGIAR). Support is also given by the Governments of Ghana, Pakistan, South Africa, Sri Lanka and Thailand. The authors: Intizar Hussain is a Senior Researcher (Economist) at IWMI, Liqa Raschid is a Senior Regional Researcher at IWMI, Munir A. Hanjra is a graduate student who worked collobratively with IWMI, Fuard Marikar is a Consultant with IWMI and Wim van der Hoek is a Medical Doctor, Epidemiologist, and Consultant to the Water, Health and Environment Theme of IWMI. Hussain I.; L. Raschid; M. A. Hanjra; F. Marikar; W. van der Hoek. 2002. Wastewater use in agriculture: Review of impacts and methodological issues in valuing impacts. (With an extended list of bibliographical references). Working Paper 37. Colombo, Sri Lanka: International Water Management Institute. / wastewater / water management / water quality / groundwater recharge / water reuse / cost benefit analysis / agricultural production / domestic water / water pollution / public health / economic aspects / ecology / developing countries / China / India / Mexico / Pakistan / ISBN 92-9090-472-0 Copyright © by IWMI. All rights reserved Please send inquiries and comments to: [email protected] ii Contents Acronyms .................................................................................................................. v 1. Introduction............................................................................................................... 1 1.1. Objectives and organization of the paper ....................................................... 2 2. Wastewater Characteristics ...................................................................................... 2 2.1 Sources of Wastewater .................................................................................... 2 2.2 Characteristics of Wastewater flow ................................................................ 3 2.3 Composition of Wastewater ............................................................................ 3 3. Existing Approaches for Regulating Wastewater Reuse in Agriculture ................. 5 3.1 Microbiological guidelines for Wastewater Reuse ......................................... 5 3.2 Chemical Guidelines for Wastewater Reuse .................................................. 7 3.3 Religious Perspective on Wastewater Irrigation in the context of Pakistan.. 7 4. Choice of (Cost-Effective) Wastewater Treatment Systems for Irrigation ............. 7 4.1 Wastewater Treatment Using Land-Based Systems—Quality and Cost Considerations.................................................................................. 8 5. Review of Potential Impacts of Wastewater Use in Agriculture ............................ 9 5.1 Public Health ................................................................................................... 10 5.2 Crops ................................................................................................................ 10 5.3 Soil Resources ................................................................................................. 11 5.4 Groundwater Resources .................................................................................. 12 5.5 Property Values................................................................................................ 13 5.6 Ecological Impacts ......................................................................................... 13 5.7 Social Impacts.................................................................................................. 13 6. Economics of Wastewater Irrigation—a Selective Review of Empirical Information .............................................................................................. 14 7. Techniques for Economic Valuation of Impacts...................................................... 16 7.1 Limitations of Valuation Techniques .............................................................. 18 8. Economic Valuation in Practice ............................................................................... 18 8.1 Approach to date and its limitations ............................................................... 18 8.2 A suggested framework for valuing impacts .................................................. 20 8.3 Public Health ................................................................................................... 21 8.4 Crops ................................................................................................................ 22 8.5 Soil Resources ................................................................................................. 24 8.6 Groundwater Resources .................................................................................. 25 8.7 PropertyValues ................................................................................................. 26 8.8 Ecological Impacts .......................................................................................... 27 iii 8.9 Social Impacts.................................................................................................. 27 8.10 Indirect Impacts ............................................................................................... 27 Annex 1 Note on Environmental Valuation Techniques ............................................... 29 Annex 2 Summary of Empirical Evidence of Public Health Effects of Wastewater Reuse ....................................................................................... 31 Annex 3 Summary of Empirical Evidence of Effects of Wastewater Irrigation on Crops .......................................................................................... 32 Annex 4 Bibliography .................................................................................................... 37 Tables Table 1. Pollutants and contaminants in wastewater and their potential impacts through agricultural use ......................................................................... 4 Table 2. Composition of raw wastewater.......................................................................... 5 Table 3. Taxonomy of economic valuation techniques .................................................... 17 Table 4. Applicability of valuation techniques to environmental impacts ...................... 18 Table 5. Comparisons of valuation methodologies ........................................................... 18 iv Acronyms As Arsenic B Boron BOD Biochemical oxygen demand Ca Calcium Cl- Chloride COD Chemical oxygen demand Cd Cadmium EC Electrical conductivity Hg Mercury K Potassium Mg Magnesium Na Sodium N Nitrogen Ni Nickel P Phosphorus Pb Lead pH Hydrogen ion concentration SS Suspended solids TDS Total dissolved solids TKN Total kjeldahl nitrogen TP Total phosphorus Zn Zinc v Wastewater Use in Agriculture: Review of Impacts and Methodological Issues in Valuing Impacts Intizar Hussain Liqa Raschid Munir A. Hanjra Fuard Marikar and Wim van der Hoek Introduction With increasing global population, the gap between the supply and demand for water is widening and is reaching such alarming levels that in some parts of the world it is posing a threat to human existence. Scientists around the globe are working on new ways of conserving water. It is an opportune time, to refocus on one of the ways to recycle water—through the reuse of urban wastewater, for irrigation and other purposes. This could release clean water for use in other sectors that need fresh water and provide water to sectors that can utilize wastewater e.g., for irrigation and other ecosystem services. In general, wastewater comprises liquid wastes generated by households, industry, commercial sources, as a result of daily usage, production, and consumption activities. Municipal treatment facilities are designed to treat raw wastewater to produce a liquid effluent of suitable quality that can be disposed to the natural surface waters with minimum impact on human health or the environment. The disposal of wastewater is a major problem faced by municipalities, particularly in the case of large metropolitan areas, with limited space for land- based treatment and disposal. On the other hand, wastewater is also a resource that can be applied for productive uses since wastewater contains nutrients that have the potential for use in agriculture, aquaculture, and other activities. In both developed and developing countries, the most prevalent practice is the application of municipal wastewater (both treated and untreated) to land. In developed countries where environmental standards