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The alluvial plain South of Tehran, which includes fertile soils is, to a great extent, under vegetable cultivation. Irrigation water is supplied through either ground water sources, like qanats and, mostly wells, and also from surface water. The surface water is supplied by collecting the sewage effluent from residential, industrial, and commertial areas of the city, and most of the vegetable crops in the south region are directly irrigated with the sewage. Following the announcement of the media of possible pollution of vegetables, the consumers have paid much more attention to the subject in the last few years.
For investigation the sewage quality, and to find out a feasible solution for purification, a study was conducted in 1984, and sewage samples were collected and analyzed for the degree of treatabilty. Based on the results of this study and the experiences of other .countris under similar conditions, the application of stabilization ponds was considered to be the most suitable sewage treatment method.