Reuse of Wastewater for Agriculture

In rural and peri-urban areas of most developing countries, the use of sewage and wastewater for irrigation is a common practice. Wastewater is often the only source of water for irrigation in these areas. Even in areas where other water sources exist, small farmers often prefer wastewater because its high nutrient content reduces or even eliminates the need for expensive chemical fertilizers.

Concern for human health and the environment are the most important constraints in the reuse of wastewater. While the risks do need to be carefully considered, the importance of this practice for the livelihoods of countless smallholders must also be taken into account. The aim of IWMI research on wastewater irrigation is to maximize the benefits to the poor who depend on the resource while minimizing the risks.

Wastewater irrigation provides income for small farmers

Many wastewater irrigators are not landowning farmers, but landless people that rent small plots to produce income-generating crops such as vegetables that thrive when watered with nutrient-rich sewage. Across Asia, Africa and Latin America these wastewater micro-economies support countless poor people. Stopping or over-regulating these practices could remove the only income many landless people have.

Is wastewater treatment the best option?

Affluent countries regard wastewater treatment as vital to protect human health and prevent the contamination of lakes and rivers. But for most developing countries this solution is prohibitively expensive. In this case, applying wastewater to agricultural lands is a more economical alternative—and more ecologically sound than uncontrolled dumping of municipal and industrial effluents into lakes and streams.

How do we make this widespread practice safer for people and environment?

Obviously the short-term benefits of wastewater irrigation could be offset by the health and environmental impacts. The first step is to scientifically evaluate these. Once the actual risks are clear, we can work to reduce them. This means, for example, finding affordable ways of monitoring the presence of harmful contaminants in wastewater, such as heavy metals that can accrue in soil and crops. It means looking at farming practices and crops grown to find ways of minimizing risks of infection for farmers and consumers.

IWMI's research in Pakistan, Ghana, Vietnam and Mexico examines both positive and negative impacts of wastewater reuse for agriculture. This work will result in tools and concepts that can help policy makers and planners balance the needs of small farmers with the health of people and the environment.

A nationwide assessment of wastewater use in Pakistan: an obscure activity or a vitally important one? Jeroen H.J. Ensink, Tariq Mahmood, Wim van der Hoek, Liqa Raschid-Sally and Felix P. Amerasinghe Confronting the realities of wastewater use in agriculture. Water Policy Briefing - Issue 9. Use of Untreated Wastewater in Peri-Urban Agriculture in Pakistan: Risks and Opportunities. IWMI Research Report 64. Available on-line in PDF format 360KB - requires Adobe Acrobat Reader™. Urban Wastewater: A Valuable Resource for Agriculture. A Case Study from Haroonabad, Pakistan. IWMI Research Report 63. Available on-line in PDF format 477KB - requires Adobe Acrobat Reader™. Urban wastewater reuse for crop production in the water-short Guanajuato River Basin, Mexico. IWMI Research Report 41. Available on-line in PDF format 2.85 MB - requires Adobe Acrobat Reader™. Feenstra, S.; Hussain, R.; van der Hoek, W. (2000). Health Risks of Irrigation with Untreated Urban Wastewater in the Southern Punjab, Pakistan. IWMI Pakistan Report 107. view abstract Available on-line in PDF format 123KB - requires Adobe Acrobat Reader™.

Improving the performance of wastewater irrigation in peri-urban areas, Pakistan Identifying and validating the benefits of wastewater irrigation and practices for sustainable use. more information>> Solid and liquid waste recycling for (peri-)urban agriculture, Ghana Analyzing options on co-composting of solid waste with faecal sludge and of safe wastewater reuse for urban and peri-urban agriculture.more information>> Environmental and human health aspects of wastewater irrigation, Vietnam Evaluating potential costs and benefits of this practice and developing recommendations for sustainable use. more information>> Balancing the economic and ecological concerns of wastewater irrigation, Mexico Examining the economic benefits to farmers of wastewater irrigation and the health and environmental risks involved. more information>>

What low-cost measures can miminize the health hazards of wastewater reuse for agriculture?

Research in Haroonabad, Pakistan, a small town where domestic wastewater is used for irrigation, identified several simple practices that could reduce health risks to farmers and the community. These include : Farmer wades through homemade diversion canal, which carries wastewater to his fields. Wearing shoes and gloves while working in wastewater irrigated fields Regular treatment of farmers and their families with antihelmintic drugs to prevent worm infections Crop restrictions in wastewater irrigated fields Better information on hygiene behavior and risks of wastewater irrigation for farmers

Guidelines The World Health Organization's influential Guidelines for the Safe Use of Wastewater and Excreta in Agriculture and Aquaculture (1989) can be ordered via the WHO website for - an executive summary can be downloaded free of charge. A reassessment of the WHO guidelines in light of more recent research is available on the WELL (Water and Environmental Health at London and Loughborough) website. The United States Environmental Protection Agency also offers water quality guidelines (1992) for wastewater used in irrigating various vegetation and crops in its Guidelines for Water Reuse Manual, which can be ordered on-line free of charge.