WHO GUIDELINES FOR THE
SAFE USE OF WASTEWATER ,
EXCRETA AND GREYWATER
VOLUME II
WASTEWATER USE IN AGRICULTURE
GUIDELINES FOR THE SAFE USE OF WASTEWATER, EXCRETA AND GREYWATER
Volume 2
Wastewater use in agriculture
ii
WHO Library Cataloguing-in-Publication Data
WHO guidelines for the safe use of wastewater, excreta and greywater / World Health Organization.
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 in agriculture.
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 in agriculture.
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
All rights reserved. Publications of the World Health Organization can be obtained from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel: +41 22 791 2476; fax: +41 22 791 4857; email: bookorders@who.int). Requests for permission to reproduce or translate WHO publications – whether for sale or for noncommercial distribution – should be addressed to WHO Press, at the above address (fax: +41 22 791 4806; email: permissions@who.int).
The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement.
The mention of specific companies or of certain manufacturers’ products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters.
All reasonable precautions have been taken by WHO to verify the information contained in this publication. However, the published material is being distributed without warranty of any kind, either express or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall the World Health Organization be liable for damages arising from its use.
Printed in France.
iii
List of acronyms and abbreviations . . . .vi
Preface . . . .vii
Acknowledgements . . . .ix
Executive summary . . . .xiii
1. Introduction . . . .1
1.1 Objectives and general considerations . . . .1
1.2 Target audience, definitions and scope . . . .2
1.3 Driving forces behind increasing wastewater use . . . .3
1.3.1 Increasing water scarcity and stress . . . .3
1.3.2 Increasing population . . . .3
1.3.3 Wastewater as a resource . . . .4
1.3.4 The Millennium Development Goals . . . .5
1.4 Organization of this Guidelines document . . . .6
2. The Stockholm Framework . . . .9
2.1 A harmonized approach to risk assessment/management . . . .9
2.2 Assessment of environmental exposure . . . .12
2.3 Assessment of health risk . . . .14
2.4 Tolerable health risk . . . .15
2.5 Health-based targets . . . .15
2.6 Risk management . . . .16
2.7 Public health status . . . .18
2.7.1 Excreta-related diseases . . . .19
2.7.2 Schistosomiasis . . . .21
2 7.3 Vector-borne diseases . . . .21
2.7.4 Measuring public health status . . . .21
3. Assessment of health risk . . . .23
3.1 Microbial analysis . . . .24
3.1.1 Survival of pathogens in soil and on crops . . . .26
3.2 Epidemiological evidence . . . .31
3.2.1 Risks to consumers of crops eaten uncooked . . . .33
3.2.2 Risks to agricultural workers and their families . . . .35
3.2.3 Risks to local communities from sprinkler irrigation . . . .45
3.2.4 Overall results for farming families and local communities . . . .46
3.3 Quantitative microbial risk analysis . . . .47
3.4 Emerging issues: infectious diseases . . . .53
3.5 Chemicals . . . .53
3.5.1 Health impacts . . . .54
3.5.2 Assessing the risks from chemical contaminants . . . .55
3.5.3 Emerging issues: chemicals . . . .56
4. Health-based targets . . . .59
4.1 Tolerable burden of disease and health-based targets . . . .59
4.1.1 Step 1: Tolerable risk of infection . . . .59
4.1.2 Step 2: QMRA . . . .61
4.1.3 Step 3: Required pathogen reduction . . . .61
4.1.4 Step 4: Health-based protection measures to achieve required pathogen reduction . . . .61
CONTENTS
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4.1.5 Step 5: Verification monitoring . . . .61
4.1.6 Example derivation of microbial performance targets . . . .61
4.2 Microbial reduction targets . . . .63
4.2.1 Unrestricted irrigation . . . .63
4.2.2 Restricted irrigation . . . .67
4.2.3 Localized irrigation . . . .69
4.3 Verification monitoring . . . .69
4.3.1 Wastewater treatment . . . .69
4.3.2 Other health protection measures . . . .70
4.4 Food exports . . . .70
4.5 National standards: variations from ≤10–6DALY per person per year . . . .71
4.6 Chemicals . . . .72
4.6.1 Health-based targets . . . .72
4.6.2 Physicochemical quality of treated wastewaters for plant growth requirements . . . .74
5. Health protection measures . . . .75
5.1 Crop restriction . . . .76
5.2 Wastewater application techniques . . . .76
5.2.1 Flood and furrow irrigation . . . .76
5.2.2 Spray and sprinkler irrigation . . . .77
5.2.3 Localized irrigation . . . .77
5.2.4 Cessation of irrigation . . . .78
5.3 Pathogen die-off before consumption . . . .78
5.4 Food preparation measures . . . .78
5.5 Human exposure control . . . .79
5.5.1 Fieldworkers . . . .79
5.5.2 Consumers . . . .79
5.5.3 Chemotherapy and immunization . . . .80
5.6 Wastewater treatment . . . .80
5.6.1 Low-rate biological systems . . . .84
5.6.2 High-rate processes . . . .87
5.7 Raw wastewater use . . . .89
6. Monitoring and system assessment . . . .93
6.1 Monitoring functions . . . .93
6.2 System assessment . . . .93
6.3 Validation . . . .94
6.4 Operational monitoring . . . .96
6.5 Verification monitoring . . . .97
6.6 Small systems . . . .100
6.7 Other types of monitoring . . . .100
6.7.1 Food inspection . . . .100
6.7.2 Public health surveillance . . . .100
7. Sociocultural aspects . . . .101
7.1 Cultural and religious beliefs . . . .101
7.2 Public perception . . . .102
7.2.1 Public acceptance of wastewater use schemes . . . .103
8. Environmental aspects . . . .107
8.1 Components of wastewater . . . .108
8.1.1 Pathogens . . . .108
8.1.2 Salts . . . .109
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8.1.3 Heavy metals . . . .109
8.1.4 Toxic organic compounds . . . .110
8.1.5 Nutrients . . . .112
8.1.6 Organic matter . . . .113
8.1.7 Suspended solids . . . .114
8.1.8 Acids and bases (pH) . . . .114
8.2 Environmental effects through the agricultural chain . . . .114
8.2.1 Soils . . . .114
8.2.2 Groundwater . . . .121
8.2.3 Surface water . . . .125
8.3 Management strategies for reducing environmental impacts . . . .126
9. Economic and financial considerations . . . .129
9.1 Economic feasibility . . . .129
9.1.1 Cost–benefit analysis . . . .129
9.1.2 Costs and benefits . . . .132
9.1.3 Multiple objective decision-making processes . . . .135
9.2 Financial feasibility . . . .135
9.3 Market feasibility . . . .138
10. Policy aspects . . . .139
10.1 Policy . . . .139
10.1.1 International policy . . . .140
10.1.2 National wastewater use policies . . . .140
10.1.3 Wastewater in integrated water resources management . . . .141
10.2 Legislation . . . .142
10.2.1 Institutional roles and responsibilities . . . .143
10.2.2 Rights of access . . . .145
10.2.3 Land tenure . . . .145
10.2.4 Public health . . . .145
10.3 Regulations . . . .146
10.4 Developing a national policy framework . . . .146
10.4.1 Defining objectives . . . .146
10.4.2 Assessment of policy environment . . . .147
10.4.3 Developing national approaches based on the WHO Guidelines .148 10.4.4 Research . . . .148
11. Planning and implementation . . . .151
11.1 Reporting and communication . . . .153
11.2 Interaction with community and consumers . . . .153
11.3 Use of data and information . . . .155
11.4 Project planning criteria . . . .155
11.4.1 Support services . . . .157
11.4.2 Training . . . .158
References . . . .159
Annex 1: Good irrigation practice . . . .177
Annex 2: Summary of impacts of heavy metals and trace elements associated with wastewater irrigation . . . .185
Annex 3: Health impact assessment . . . .189
Annex 4: Glossary of terms used in the Guidelines . . . .191
vi
LIST OF ACRONYMS AND
ABBREVIATIONS
vii
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 irrigation
Unrestricted irrigation
A B C D E F G H
Root Leaf
W W DO
DO
T T
T
T
T
T
T
T DIH
DIL
SSI Labour intensive Highly mechanized Log10
pathogen reduction
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1
1
INTRODUCTION
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Guidelines for the safe use of wastewater, excreta and greywater
9 8 7 6 5 4 3 2 1 0 Population (billions)
1995 2025 2050
Population without water scarcity
Population with water scarcity
Year 2.8
4
0.46
5 Volume 2: Wastewater use in agriculture
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Guidelines for the safe use of wastewater, excreta and greywater
7 10. Policy aspects
11. Planning and implementation 4. Health-based
targets
5. Health protection measures 6. Monitoring
and system assessment 1. Introduction
Guidelines
7. Sociocultural aspects 8. Environmental
aspects 9. Economic and
financial considerations
Other information 2. Stockholm
Framework 3. Assessment of
health risk
Supporting evidence
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Health-based targets Basic control
approaches
Water/waste quality objectives
Other management objectives
Define measures and interventions (requirements, specifications) based
on objectives
Assessment of health risk Assess
environmental exposure
Public health status
Tolerable health risk
Define key risk points and audit procedures for overall system
effectiveness
Define analytical verifications (process, public health)
9
2
THE STOCKHOLM FRAMEWORK
Health risk management
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Table 2.1 (continued)
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Table 2.2 (continued)
(continued)
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Treatment
Application of wastes - allowing die-off periods
Produce restriction Control of trematode intermediate hosts Prevention of cross- contamination Post-harvest processing Food hygiene Cooking food
Consumer Hazard
Treatment Personal protective equipment Access to safe drinking-water and sanitation near facilities
Control of vectors and intermediate hosts
Personal hygiene
Workers and families Hazard
Treatment Access to safe drinking-water and sanitation for local communities Restrict public access to ponds Control of vectors and intermediate hosts
Vector barriers, repellents, prophylactics
Local communities
Hazard
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Table 2.5 (continued)
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3
ASSESSMENT OF HEALTH RISK
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Table 3.10 (continued)
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Table 3.11 (continued) (continued)
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Table 3.12 (continued)
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Table 3.12 (continued)
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Table 3.13 (continued)
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4
HEALTH-BASED TARGETS
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65 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 irrigation
Unrestricted irrigation
A B C D E F G H
Root Leaf
W
W DO
DO
T T
T T
T
T
T
T DIH
DIL
SSI Labour intensive Highly mechanized Log10
pathogen reduction
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Table 4.7 (continued)
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5
HEALTH PROTECTION MEASURES
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83 Table 5.3 (continued)
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Table 5.3 (continued)
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Box 5.1 (continued)
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93 93
6
MONITORING AND SYSTEM
ASSESSMENT
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95 Assemble the team to prepare the risk management plan
Document and describe the system
Undertake a hazard assessment and risk characterization to identify and understand how risks
can be managed in the system
Assess the existing or proposed system (including a description of the system and a flow diagram)
Identify control measures — the means by which risks can be controlled
Define monitoring of control measures — what limits define acceptable performance and how
these are monitored
Establish procedures to verify that the risk management plan is working effectively and will meet
the health-based targets
Develop supporting programmes (e.g. training, hygienic practices, standard operating procedures, upgrade and
improvement, research and development, etc.)
Prepare management procedures (including corrective actions) for normal and incident conditions
Establish documentation and communication procedures
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99 Table 6.2 (continued)
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101 101
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SOCIOCULTURAL ASPECTS
102 102
103 103
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104 100.0
80.0 60.0 40.0 20.0 0.0
Agree
Firef ighting
Golf irrigation Lawn irrigation
Car w ashing
Agricultural ir
rigation Laundr y
Recreational reser voir
Groundw ater rechar
ge
% surveyed
Not sure Disagree
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105 General survey
Plan of study
Public notification/
involvement
Specific users survey
Identification and evaluation of alternatives
Public meetings
Customer-specific workshops
Plan selection
Public notification/
involvement
Customer-specific information programme
Project implentation
107 107
8
ENVIRONMENTAL ASPECTS
Sewage Industrial discharges
Evaporation
Wastewater treatment plant (in developing countries)
Sewerage system
Irrigation channels Infiltration
Storage dam Aquaculture
Aquatic plants
Sprinklers
Evaporation
River
Irrigation drainage
Aquatic plants
Lake
Cattle consuming irrigated crops
Consumer Crops Cattle Water
Aquifer Water + salts Infiltration
Soil
(retains metals, organic matter and phosphorus)
Compounds and water absorption by plants
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Table 8.1 (continued)
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Table 8.1 (continued) (continued)
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Table 8.1 (continued) (continued)
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Table 8.1 (continued) (continued)
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Table 8.1 (continued) (continued)
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Water balance in Mexico City and the Mezquital Valley
29 m3/s from groundwater and surface water from basins requiring pumping
1200 m from 300 km
62 m3/s Mexico City water supply
12 m3/s of rainwater and 48 m3/s of municipal wastewater
8 m3/s urban reuse
52 m3/s of wastewater
100 m
25 m3/s of wastewater infiltration 25m3/s of natural recharge 33m3/s from groundwater
Mexico City aquifer
Mezquital Valley aquifer
70 km
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Box 8.3 (continued)
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Table 8.5 (continued)
129 129
9
ECONOMIC AND FINANCIAL
CONSIDERATIONS
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Table 9.1 (continued)
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POLICY ASPECTS
Policy
International National Local
Legislation Institutional framework
Regulation application
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Box 10.1 (continued)
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PLANNING AND IMPLEMENTATION
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Sustainable project planning
Health
Environmental impact
Social impact and public perception Institutional
feasibility Technical feasibility
Economic feasibility
Market feasibility
Financial feasibility
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REFERENCES
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