Wastewater use in agriculture

Wastewater use in agriculture

The use of sewage and wastewater for irrigation is a common practice in rural and peri-urban areas of most developing countries. 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. Many wastewater irrigators are not landowning farmers, but landless people who rent small plots to produce income-generating crops such as vegetables that thrive when watered with nutrient-rich sewage. These wastewater micro-economies support countless poor people across Asia, Africa and Latin American. Terminating or over-regulating these practices could take away the only opportunity of income that many landless people have. 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. Affluent countries regard wastewater treatment as vital to protect human health and prevent the contamination of lakes and rivers. However, this solution is prohibitively expensive for most developing countries. In this case, applying wastewater to agricultural lands is a more economical alternative and is more ecologically sound than the uncontrolled dumping of municipal and industrial effluents into lakes and streams. Obviously, the short-term benefits of wastewater irrigation could be offset by the health and environmental impacts. The first step is to scientifically evaluate the risks. Once the actual risks are clear, risk reduction efforts can then be carried out. This means that, 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 also means looking at farming practices and crops grown to find ways of minimizing the risks of infection to farmers and consumers. The aim of IWMI’s research on wastewater irrigation is to maximize the benefits to the poor (who depend on the resource) while minimizing the risks. Studies in Pakistan, Ghana, Vietnam and Mexico have examined both the positive and negative impacts of wastewater reuse for agriculture. Current IWMI work on wastewater can be found Key research questions What are the dangers of uncontrolled wastewater irrigation in terms of public health and pollution? How can the nutrient value of wastewater be assessed? What sustainable practices are being used that can be transferred to benefit poor rural areas in other countries? From a public health perspective, which crops are the best candidates for wastewater irrigation and which should be avoided?