MONITORING THE QUALITY OF SECONDARY EFFLUENTS REUSED FOR UNRESTRICTED IRRIGATION AFTER UNDERGROUND-STORAGE

A new wastewater reclamation system in Israel supplied 75 million cubic metres of water for unresticted irrigation during the first year of operation and is designed to supply up to 135 million cubic metres per year to arid and semi-arid areas of the country in the future. It consists of biological-mechanical treatment of the raw sewage of Greater Tel-Aviv, spreading and infiltration of the secondary effluents over large sand dunes for soil-aquifer treatment (SAT), storage in the aquifer, 52 recovery wells, a 100 km long conveying pipe and a distribution net to the irrigated areas in southern Israel. A slight decrease in some quality parameters was observed in the open floating reservoirs along the conveyance system. Nevertheless, the reclaimed water supplied during the first year of operation was of very good quality and may be used to irrigate all crops, including vegetables eaten raw, without any restriction. Careful monitoring of such large-scale schemes is essential to maintain consistent high-quality water and to achieve farmers and public acceptance.