Desalination of reclaimed wastewater to prevent salinization of soils and groundwater Original Research Article

The complete utilization of Israelʹs water potential (safe yield) (1800 Mm3/y) was combined with wide and intensive reuse of most wastewaters (300 Mm3/y), reduced to minimum water outflows to the sea. Irrigation is a “consumptive” type ofwateruse-most ofthe waterbeing “lost” by evapo-transpiration, leavingthe mineral salinity in the soil solution and in the excess (residual) water seeping, penetrating to underlying unsaturated layers on its way to groundwater. Thus, the complete use and reuse of water bring about a high rate of salt accumulation in soils, in the unsaturated zones, and eventually in groundwater. This poses a serious risk of salinization of the countryʹs lands and aquifers. Effects of salinization of soil and water are felt on a time-scale of tens of years. In several regions in Israel, salinization of the soil has already been encountered, and there is a permanent increase in water salinity at the coastal aquifer. Reports of many studies indicate a significant salinity increase in the unsaturated zones and at upper interface layers of the groundwater table. Also, accumulation (fixation) of specific heavy metals can be seen in soils irrigated with reclaimed wastewater. Though negative effects of heavy metals have not been felt up to now, the rate of accumulation predicts such effects in 10 to 30 years of continuing practices of such irrigation. The accumulation of salinity in general, combined with the accumulation of specific elements, can be defined as a chemo-desertifrcation process. Partial desalination (using membrane processes) of reclaimed wastewater is needed to reduce the salinity load, to “purge salt” from the country, and to prevent salinization of land and water to enable sustainable reuse.