guidelines for the safe use of wastewater, excreta …ii who library cataloguing-in-publication data...
TRANSCRIPT
GUIDELINES FOR THE SAFE USE OF
WASTEWATER, EXCRETA AND GREYWATER
Volume 2Wastewater use in agriculture
ii
WHO Library Cataloguing-in-Publication Data
WHO guidelines for the safe use of wastewater, excreta and greywater / World HealthOrganization.
v. 1. Policy and regulatory aspects — v. 2. Wastewater use in agriculture — v. 3. Wastewater and excreta use in aquaculture — v. 4. Excreta and greywater use inagriculture.
1. Water supply. 2. Water supply - legislation. 3. Agriculture. 4. Aquaculture. 5. Sewage.6. Wastewater treatment plants. 7. Guidelines. I. World Health Organization. II. Title:Safe use of wastewater, excreta and greywater. III. Title: Policy and regulatory aspects. IV.Title: Wastewater use in agriculture. V. Title: Wastewater and excreta use in aquaculture. VI. Title: Excreta and greywater use inagriculture.
ISBN 92 4 154686 7 (set) (NLM classification: WA 675)ISBN 92 4 154682 4 (v. 1)ISBN 92 4 154683 2 (v. 2)ISBN 92 4 154684 0 (v. 3)ISBN 92 4 154685 9 (v. 4)
© World Health Organization 2006
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List of acronyms and abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viPreface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viiAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix
Executive summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xiii
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.1 Objectives and general considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.2 Target audience, definitions and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.3 Driving forces behind increasing wastewater use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.1 Increasing water scarcity and stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31.3.2 Increasing population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31.3.3 Wastewater as a resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41.3.4 The Millennium Development Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
1.4 Organization of this Guidelines document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2. The Stockholm Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92.1 A harmonized approach to risk assessment/management . . . . . . . . . . . . . . . . . . . . . . . . .92.2 Assessment of environmental exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122.3 Assessment of health risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142.4 Tolerable health risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152.5 Health-based targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152.6 Risk management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162.7 Public health status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
2.7.1 Excreta-related diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192.7.2 Schistosomiasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212 7.3 Vector-borne diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212.7.4 Measuring public health status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
3. Assessment of health risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233.1 Microbial analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.1.1 Survival of pathogens in soil and on crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263.2 Epidemiological evidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
3.2.1 Risks to consumers of crops eaten uncooked . . . . . . . . . . . . . . . . . . . . . . . . . . .333.2.2 Risks to agricultural workers and their families . . . . . . . . . . . . . . . . . . . . . . . . .353.2.3 Risks to local communities from sprinkler irrigation . . . . . . . . . . . . . . . . . . . . .453.2.4 Overall results for farming families and local communities . . . . . . . . . . . . . . . . .46
3.3 Quantitative microbial risk analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .473.4 Emerging issues: infectious diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .533.5 Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
3.5.1 Health impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .543.5.2 Assessing the risks from chemical contaminants . . . . . . . . . . . . . . . . . . . . . . . . .553.5.3 Emerging issues: chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
4. Health-based targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .594.1 Tolerable burden of disease and health-based targets . . . . . . . . . . . . . . . . . . . . . . . . . .59
4.1.1 Step 1: Tolerable risk of infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .594.1.2 Step 2: QMRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .614.1.3 Step 3: Required pathogen reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .614.1.4 Step 4: Health-based protection measures to achieve required pathogen reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
CONTENTS
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Guidelines for the safe use of wastewater, excreta and greywater
4.1.5 Step 5: Verification monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .614.1.6 Example derivation of microbial performance targets . . . . . . . . . . . . . . . . . . . .61
4.2 Microbial reduction targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .634.2.1 Unrestricted irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .634.2.2 Restricted irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .674.2.3 Localized irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
4.3 Verification monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .694.3.1 Wastewater treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .694.3.2 Other health protection measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
4.4 Food exports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .704.5 National standards: variations from ≤10–6 DALY per person per year . . . . . . . . . . . . .714.6 Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
4.6.1 Health-based targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .724.6.2 Physicochemical quality of treated wastewaters for plant growth requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
5. Health protection measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .755.1 Crop restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .765.2 Wastewater application techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
5.2.1 Flood and furrow irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .765.2.2 Spray and sprinkler irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .775.2.3 Localized irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .775.2.4 Cessation of irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
5.3 Pathogen die-off before consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .785.4 Food preparation measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .785.5 Human exposure control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
5.5.1 Fieldworkers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .795.5.2 Consumers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .795.5.3 Chemotherapy and immunization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
5.6 Wastewater treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .805.6.1 Low-rate biological systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .845.6.2 High-rate processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
5.7 Raw wastewater use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
6. Monitoring and system assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .936.1 Monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .936.2 System assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .936.3 Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .946.4 Operational monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .966.5 Verification monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .976.6 Small systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1006.7 Other types of monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
6.7.1 Food inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1006.7.2 Public health surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
7. Sociocultural aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1017.1 Cultural and religious beliefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1017.2 Public perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
7.2.1 Public acceptance of wastewater use schemes . . . . . . . . . . . . . . . . . . . . . . . . . .103
8. Environmental aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1078.1 Components of wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
8.1.1 Pathogens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1088.1.2 Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
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8.1.3 Heavy metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1098.1.4 Toxic organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1108.1.5 Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1128.1.6 Organic matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1138.1.7 Suspended solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1148.1.8 Acids and bases (pH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
8.2 Environmental effects through the agricultural chain . . . . . . . . . . . . . . . . . . . . . . . . .1148.2.1 Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1148.2.2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1218.2.3 Surface water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
8.3 Management strategies for reducing environmental impacts . . . . . . . . . . . . . . . . . . . .126
9. Economic and financial considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1299.1 Economic feasibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
9.1.1 Cost–benefit analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1299.1.2 Costs and benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1329.1.3 Multiple objective decision-making processes . . . . . . . . . . . . . . . . . . . . . . . . . .135
9.2 Financial feasibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1359.3 Market feasibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
10. Policy aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13910.1 Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
10.1.1 International policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14010.1.2 National wastewater use policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14010.1.3 Wastewater in integrated water resources management . . . . . . . . . . . . . . . . .141
10.2 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14210.2.1 Institutional roles and responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14310.2.2 Rights of access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14510.2.3 Land tenure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14510.2.4 Public health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
10.3 Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14610.4 Developing a national policy framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146
10.4.1 Defining objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14610.4.2 Assessment of policy environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14710.4.3 Developing national approaches based on the WHO Guidelines . . . . . . . . . . .14810.4.4 Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
11. Planning and implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15111.1 Reporting and communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15311.2 Interaction with community and consumers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15311.3 Use of data and information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15511.4 Project planning criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
11.4.1 Support services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15711.4.2 Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
Annex 1: Good irrigation practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177Annex 2: Summary of impacts of heavy metals and trace elements associated with wastewater irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185Annex 3: Health impact assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189Annex 4: Glossary of terms used in the Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
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LIST OF ACRONYMS ANDABBREVIATIONS
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PREFACE
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ACKNOWLEDGEMENTS
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EXECUTIVE SUMMARY
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7
6
5
4
3
2
1
0
T = Treatment
DI = Drip irrigation (H = High crops; L = Low crops)
DO = Die-off W = Washing of produce
SSI = Subsurface irrigation
Restricted irrigationUnrestricted irrigation
A B C D E F G H
Root Leaf
W
WDO
DO
TT
T
T
T
TT
T
DIH
DIL
SSI
Labo
urin
tens
ive
Hig
hly
mec
hani
zed
Log10
pathogenreduction
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