Sustainable management of water resources by reusing urban runoff for irrigation (case study of Elahieh Canal, district 3, Municipality of Tehran)

Destruction of aquatic ecosystems, reduction of urban water quality and shortage of water caused countries to use unconventional water sources. Currently, the water resources of populated cities like Tehran are under severe pressure. In this research, the Elahieh canal in Tehran 3rd district was selected as a case study. The purpose of this study is to reuse canal water as an important method of sustainable management of water resources. The present research has investigated the supplying, purification and reuse of urban canal water with the aim of irrigating a part of the green areas in the 3rd district of Tehran. The data that is used in this research was collected by field observation method and the analyzes were done in the accredited laboratory. Some of the most important water quality results are as follows: the average amount of coliform bacteria was 1100 MPN/100cc, this value indicates microbial contamination. The presence of sodium reduces the permeability of water in the soil and inhibits the growth of plants. The amount of sodium in the water of this channel is 34 mg/lit, which has exceeded the threshold. The amount of BOD5 and COD was 38 and 72 mg/lit, respectively. Also, the heavy metal test results showed that boron exceeded the threshold with an average of 52 ppb. Finally, the testing of the samples showed that this water will be prepared for reuse by performing various stages of physical and advanced purification and also disinfection. Also, the results showed that using the Elahieh canal water for irrigation, reduces the pressure on the underground water table. Currently, 560 cubic meters per day are being pumped from the Fakhar well, if recycled water is used instead of Fakhar well, 560 cubic meters per day will be saved.