Evaluation of membrane processes to reduce the salinity of reclaimed wastewater

The problem of water shortage in Israel has been known for years. About 75% of the wastewater is treated and used for irrigation with a tendency towards increasing of this quota to the maximum. The existing municipal wastewater treatments are incapable of removing inorganic salts and this results in relatively high salt concentrations in most of the reused water flowing from domestic and industrial sources. The increased use of available sources of water and the semi-arid conditions of the area reduces the "wash-out" of excess salts. However, both phenomena cause salt accumulation in soils at the unsaturated zone, damaging crops and soil and eventually the ground water on reaching the aquifers. The RO membrane process (a common desalination method) includes pretreatment of effluents in order to reduce membrane damage and enables reliable continuous operation. The selection of a treatment method for desalination depends on the user of reused water. Suitable criteria for the water quality should be determined. Wastewater improvement can be achieved by treatment of inlets of municipal supply systems or outlets of municipal wastewater. The study gives a preliminary evaluation of the cost of desalination of wastewater by comparing the two options, including possibility and usefulness of the treatments, and equipment needed to decrease salt concentrations in effluents used mostly for irrigation purposes [1].