Guidelines for wastewater reuse in agriculture and aquaculture: recommended revisions based on new research evidence

Executive Summary 4 1. Introduction 7 2. Agricultural Reuse 8 2.1 Background 8 2.2 Current WHO Guidelines, and standards for selected countries 8 2.3 Summary of evidence supporting WHO (1989) Guidelines 11 2.3.1 Effects of use of untreated wastewater 11 2.3.1.1 Effects on farm workers or wastewater treatment plant workers 11 2.3.1.2 Effects on consumers of vegetable crops 12 2.3.2 Effects of use of treated wastewater 12 2.3.2.1 Effects on farm workers or nearby populations 12 2.3.2.2 Effects on consumers of vegetable crops 13 2.4 New evidence of health risks from epidemiological and microbiological studies in Mexico 13 2.4.1 Study area 13 2.4.2 Results: risks to farm workers related to restricted irrigation and effect of wastewater treatment 14 2.4.2.1 Exposure to raw wastewater 14 2.4.2.2 Exposure to partially treated wastewater 14 2.4.3 Risks to consumers related to unrestricted irrigation 15 2.5 New evidence of health risks from studies in other sites 16 2.5.1 Effects on farm workers or wastewater treatment plant workers 16 2.5.2 Effects on consumers of vegetable crops 17 2.5.2.1 Evidence from microbiological studies of crops irrigated with treated wastewater 17 2.5.2.2 Evidence from risk assessment studies 18 2.6 Discussion and implications of results for international guidelines and policy concerning wastewater use in agriculture. 19 2.6.1 Implications of the results for international guidelines for safe use of wastewater in agriculture 19 2.6.1.1 Approaches to setting microbiological guidelines 19 2.6.1.2 Proposed revised guidelines based on using the epidemiological perspective 21 2.6.1.3 Implications of a disease control approach in the setting of country standards 23 2.6.1.4 Issues not addressed by current international guidelines 24 2.6.2 Implications for wastewater treatment and other health protection measures 26 2.6.2.1 Wastewater treatment 26 2.6.2.2 Crop restriction 28 2.6.2.3 Irrigation technique 28 2.6.2.4 Human exposure control 28 2.6.2.5 Chemotherapeutic intervention 29 3. Aquacultural Reuse 30 3.1 Background and WHO Guidelines 30 3.2 Summary of evidence supporting WHO (1989) tentative guidelines 30 3.3 New evidence of health risks from studies in Indonesia 30 3.4 Discussion and implications of studies for international guidelines 31 4. Conclusions 34 5. References 36 3 List of Tables Table 1: Health guidelines for the use of wastewater in agriculture (WHO 1989) 9 Table 2: US-EPA/USAID Guidelines for agricultural reuse of wastewater (adapted from suggested guidelines for water reuse (US-EPA/USAID, 1992)) 10 Table 3: Examples of microbial quality standards used by various States in USA 10 Table 4: Mexican Standard governing wastewater …