Abstract
The agricultural reuse of untreated, partially treated and diluted wastewater is a common reality in and around three out of four cities in low-income countries. It is practiced in both dry and wet climates, mostly as an informal activity. In several instances, raw wastewater is used in irrigation; in the majority of the cases, however, wastewater is discharged into water bodies and thus used in diluted form. The main driving forces identified for the growth of this practice include general global scarcity of freshwater resources and contamination of water bodies traditionally used for irrigation, especially around urban centres. Estimates on the extent of this practice range widely, but figures point at about 20 million ha of land irrigated in this way, most of it in Asia, Latin America, and sub-Saharan Africa. Benefits highlighted in the cases reviewed include its reliable flow (which allows for multiple cropping across all seasons and climates), nutrient recovery, contributions to urban food supply and safeguarding of livelihoods (especially for the urban and peri-urban poor). However, health risks for farmers and consumers, such as worm infections, diarrhoea and skin diseases are major possible drawbacks, limiting formal recognition and support of wastewater irrigation. Nevertheless, low-cost interventions, as recently recommended by the World Health Organization and tested in West Africa, have shown great potential to reduce the health risks between farm and fork, especially where comprehensive wastewater treatment is not yet feasible. The development of locally appropriate risk reduction interventions should involve their users from the start in taking advantage of farmers' own innovations.