Aims and agenda

Agricultural use of untreated wastewater in low income countries (E-conference - 24 June - 5 July 2002)

Background

Use of urban wastewater in agriculture
Globally on an average 47% of the population live in urban areas. Even at the lower consumption figures of 100 -150 litres per capita per day the water consumption in Africa would be 45 mill m3 and in Asia 200 mill (Water and sanitation assessment report prepared for the 2nd World Water Forum). Most of this water returns as waste.

On the other hand agriculture consumes more than 70 percent of exploited water resources globally and cities are increasingly competing for water with agriculture.

With increasing water scarcity, it is mandatory to find alternative sources of water for irrigation. One such means is to enhance the use of urban wastewater transforming wastes into a resource to yield products needed by the population.

The use of the urban wastewater in agriculture is a widely established practice, particularly so in urban and peri-urban areas of arid and seasonally arid zones. Wastewater is used as a source of irrigation water as well as a source of plant nutrients (such as nitrogen, phosphorus and potassium) and trace elements (K, Na, etc) allowing farmers to reduce or even eliminate the purchase of chemical fertilizer and of organic matter that serves as a soil conditioner and humus replenisher Lunven (1992) estimated that one tenth or more of the world's population currently eats food produced on wastewater (but not always in a safe way).

In the developed world planned use (of treated wastewater) is more common, as is evident in Israel, Australia, Germany, and the USA. A literature review (Haruvy,1997) indicated that Israel is at the forefront of planned wastewater use with fully 70 % of the total agricultural demand for water in 2040 to be met by treated effluent.

For developing countries like India, Pakistan, China and Mexico, to quote a few examples, wastewater for irrigation originated as an unplanned often spontaneous activity and has been practiced for decades and even centuries by poor farmers in urban and peri-urban areas. Studies have concluded that an estimated 80% of wastewater may be used for irrigation, with China and South Asia making significant use of untreated waste for irrigation (Mara and Cairncross, 1989). In Latin America alone at least 500,000 ha of land is being irrigated with untreated wastewater, over half of which is in Mexico (Rodriguez et al, 1994). The same is the case in Africa where case studies (Bakker et al, 2000) in major cities in Africa (Accra, Dakar, Nairobi,) indicate the extensive use of wastewater.

Current wastewater use practices in developing countries includes official distribution of primary or secondary treated wastewater (i.e. after mechanical and biological treatment), the use of diluted wastewater from urban waterways and farmers accessing raw wastewater from open drains or buried trunk sewers.

The informal use of untreated wastewater by intra-urban and peri-urban farmers and gardeners is the most common situation. For large groups of poor citizens (as well as for some better off) access to wastewater is the main factor that determines their food security and income generating capacity. Without the wastewater their production would be limited to the rainy period and productivity would be minimal.

Health and environmental risks
However, irrigating with untreated wastewater poses serious public health risks, as sewage is a major source of excreted pathogens - the bacteria, viruses, protozoa- and the helminths (worms) that cause gastro-intestinal infections in human beings. Wastewater may also contain highly poisonous chemical toxins from industrial sources. Relevant groups of chemical contaminants are heavy metals, hormone active substances (HAS) and antibiotics. The risks associated with these substances may, in the long run, turn out to constitute a greater threat to public health and be more difficult to deal with than the risks from excreted pathogens.

Unregulated and continuous irrigation with sewage water may lead to problems such as soil structure deterioration (soil clogging), salinisation and phytotoxicity. . The abovementioned risks are not limited to official wastewater but often also apply to rivers and other open water sources, as indicated by figures gathered by Westcott: 45% of 110 rivers tested carried faecal coliforms levels higher than the WHO standard for unrestricted irrigation (FAO, unpublished, cited in Birley and Lock, 1999).

Treatment of wastewater
In order to prevent health risks treatment, is normally recommended as the main solution. There exists a large array of technological and process options for wastewater treatment. Centralised, technologically complex and capital-intensive treatment systems have received the most attention to date. Decentralised, low-cost options, eco-technologies and eco-sanitation approaches have only recently received more attention.

However, in practice most cities in low income countries are not able to treat more than a modest percentage of the wastewater produced in the city, due to low financial, technical and/or managerial capacity, the quick and unplanned growth of the city and the multiple and dispersed outlets of the wastewater. In many cities a large part of the wastewater is disposed of untreated to rivers and seas, with all related environmental consequences and health risks. The perspectives regarding the increase in wastewater treatment capacity in these cities are bleak. It may safely be assumed that urban farmers and gardeners increasingly will use urban wastewater for irrigation, irrespective of the municipal regulations and quality standards for irrigation water.

Alternative and complementary measures
Against this background the organisers have chosen to focus this electronic conference on the strategies that may be applied to reduce the health risks associated with the use of untreated, partially treated or diluted wastewater in agriculture whilst maintaining or enhancing the social and economic benefits for the poor urban citizens involved in irrigated production. Rather than focusing on (end of pipe) treatment of wastewater, we want to discuss:

1. Strategies to ensure proper health risk management by the users of the untreated or partially treated wastewater;
2. Strategies to prevent and reduce chemical pollution by industries of domestic sewage water and rivers that are used for irrigation.

Planning for the improved management of wastewater for reuse in urban agriculture encompasses a wide range of aspects and activities. These comprise, among others, stakeholders involvement (concepts and operational patterns), strategic water resources planning, treatment at the source of pollution and separation of wastewater flows (especially between household water and industrial wastewater), farmers education on risk management strategies (e.g. appropriate choice of crops and appropriate selection and timing, of irrigation techniques), improved institutional coordination (especially between agriculture, health, sanitation sectors); revision of municipal regulations and standards and enforcement of regulations at farmers level and vis-à-vis polluting industries, monitoring of the quality of wastewater and agricultural products, and training of professionals on sound alternatives for sanitation and recycling, among others.

Objective

To exchange, analyse and discuss strategies - as alternatives or complementary to wastewater treatment - to reduce the associated health and environmental risks of using "untreated" urban wastewater in agriculture, while maintaining or enhancing the socio-economic benefits

Intended Participants

The conference is a platform to facilitate exchange of experiences and debate between:

• Urban planners, representatives of municipal departments and policy advisors;
• Researchers (universities, research centres, thematic networks);
• Technical staff of NGO's, international and local projects, and other persons that have interest in these issues.

Outputs

The moderators will produce a summary of the discussions in each group at the end of the first and second week. At the end of the second week also the conclusions and recommendations emerging from the discussions will be drafted by the moderators and send to all participants. The results of the E-conference, together with the results of regional workshops on these topics in West Africa and South East Asia, will be used to prepare a policy paper on the use of untreated wastewater for the World Water Forum in March 2003.

A selection of the most interesting contributions to the E-conference will be included in the special issue of the Urban Agriculture Magazine on this topic.

Discussion papers and key issues

Agricultural use of untreated wastewater in low income countries (E-conference - 24 June - 5 July 2002)

Topic 1

Strategies to ensure proper management by the farmers of the health and environmental risks associated with the use of untreated wastewater.

Discussion Paper Topic 1

Topic 1 - Key Issues

• Is it meaningful to develop a typology for wastewater that is being used for urban and peri-urban agriculture? What categories of "untreated" urban wastewater should be distinguished?
• Will the use of untreated wastewater in agriculture -in the country/city you report on- probably decrease or increase in the coming decade? Why?
• What are the health and environmental effects (positive/negative) of using untreated, partially or unsuccessfully treated or diluted wastewater in agriculture that have been documented in your country/city? Which categories of the population are mainly affected? Can we speak -in the cases you report on- of acceptable risks? Why yes or no?
• What are the socio-economic costs and benefits of use of untreated wastewater in agriculture that have been documented in your country/city? Who are the main beneficiaries? Do these costs/benefits justify local government support and investment? Why yes or no?
• How effective are the local policies and regulations (national level, city level) regarding use of urban wastewater in agriculture? What policy has proven to work and which not? Why? What are the main barriers for the development of more effective policies and regulations?
• How effective are the local institutional mechanisms with respect to the design and implementation of strategies of wastewater use in agriculture? What are the main shortcomings and obstacles? How to improve? What actors should be involved and in what role? In your experience will local authorities be more amenable to formulating realistic regulations if costs and benefits were quantified?
• What are the limitations and pre-conditions to the application of crop restriction as an effective instrument to reduce health risks of use of untreated wastewater in agriculture? What are the pros and cons? When to apply?
• To what extent are farmer education and technical assistance effective instruments to reduce the health and environmental risks related to reuse of untreated wastewater? When yes, when no? What are the main issues that require attention?
• Could economic incentives and/or farmer education provide an alternative to legal restrictions to promote adequate crop choice and wastewater management?
• Is periodic monitoring of the quality of the irrigation water and/or the produce, in the areas irrigated with wastewater, a useful tool in helping to reduce the health and environmental risks? Are the present standards for irrigation water quality realistic?
• What are the strategies for improvement recommended by the local farmers themselves?
• What other strategies could be applied effectively? On what experiences is your recommendation based?

Topic 2

Strategies to ensure prevention and reduction of industrial contamination of domestic sewage and rivers that are used for irrigation. Discussion Paper Topic 2

Topic 2 - Key Issues

• Will the industrial discharge of polluted wastewater to rivers and sewers increase or decrease during the next decade in the country/city you are reporting on? Why?
• Have local authorities in the city you report on; the capacity to detect and monitor the sources of industrially polluted wastewater, its disposal, the concentration of hazardous chemicals in domestic sewage and the levels of contamination in rivers? What can be done to improve this capacity?
• What are the main barriers for industries to accept strategies to reduce the generation of hazardous wastes and to enhance the recycling of industrial waste water. What are –in your experience- the most effective strategies to overcome these barriers?
• Is the provision of information and technical assistance (on waste minimization and recycling strategies and technologies) an effective instrument to reduce the discharge of hazardous wastes in rivers and sewers and to encourage waste reduction and waste reuse and recycling? Why yes or no? Under what circumstances?
• To what extent does the creation and enforcement of regulations on the generation and discharge of hazardous wastes constitute an effective control and regulation instrument? Why yes or no? What are important pre-conditions? How effective are the actual regulations and what limits their enforcement?
• Is –in your experience- the provision of economic incentives an effective strategy to encourage waste reduction and waste reuse and recycling? Why yes or no? When to apply?
• In what ways can the separate disposal of industrial wastewater and domestic wastewater be enforced? Under what conditions?
• What are the strategies for improvement recommended by local industries themselves? What are the differences between "big" and "small" polluters?
• What other strategies may be applied effectively? What are their pros and cons?
• What can be the role and contributions of local NGO’s and farmer organizations?

Process of the Discussions

During the first week of the conference we will focus the discussions in both topics on the analysis of the actual situation and trends and the analysis of the effectivity of certain strategies.

During the second week of the conference we will continue that discussion but with more emphasis on the formulation of recommendations for policy development and action planning.

Case studies

Agricultural use of untreated wastewater in low income countries (E-conference - 24 June - 5 July 2002)

Strategies to ensure proper management by farmers

Strategies to reduce industrial contamination

Weekly summaries

Agricultural use of untreated wastewater in low income countries (E-conference - 24 June - 5 July 2002)

Summaries of week 1

• Topic 1
• Topic 2

Summaries of week 2

• Topic 1
• Topic 2

Final conclusions and recommendations

Agricultural use of untreated wastewater in low income countries (E-conference - 24 June - 5 July 2002)

Document contents:

• Introduction
• Objective
• Participants
• Thematic areas and key issues
• Metholodogy
• Synthesis and recommendations for topic 1
• Synthesis and recommendations for topic 2
• The organisers

Download final conclusions
[82 KB]