Irrigation Reuse of Pond Effluents in Developing Countries

Abstract

The large-scale reuse of sewage for irrigation, often without adequate safeguards, is commonplace in many arid and semiarid regions of the world. A UNDP/World Bank global research project has reviewed available epidemiological data and formulated a risk model to evaluate sanitary control options for effluent irrigation. The study concluded that wastewater treatment processes that effectively remove all or most of the pathogens in wastewater provide a major or total reduction in the negative health effects caused by raw wastewater reuse. Furthermore, the study found the recommended criteria for effective wastewater treatment for irrigation reuse in developing countries to be, in order of priority: (1) maximum removal of helminths; (2) effective reduction in bacterial and viral pathogens; and (3) freedom from odor and appearance nuisances (i.e., reduction of BOD). Multicell stabilization ponds are suited to meet all three criteria. Research sponsored by the UNDP/World Bank project has shown that well-designed and operated multicell stabilization ponds achieve virtually total removal of helminths and a greater than 99.99 percent reduction of enteric bacteria. Waste stabilization ponds can produce an odor-free effluent rich in nutrients and attractive for agricultural use. Most suitable in hot developing countries, ponds are a particularly robust, flexible, and almost fail-safe treatment system having low construction and operation costs. Research is now focusing on management and policy issues required to effectively achieve controlled irrigation reuse.