Salt reduction in municipal sewage allocated for reuse: the outcome of a new policy in Israel

摘要

Israel is presently reusing about 70% of its sewage and the buildup of salts in soils has been detected in some areas of the country. Prevention of sewage salt enrichment is one of the most immediately available solutions. The discharge of brines to municipal sewers is now prohibited and they are discharged to the sea. Discharge of brines to the sea has increased from 580,000 m~3 in 1999 to more than 700,000 m~3 in 2002. These salts are thus definitively taken out of the reuse cycle, year after year. The concentration of salts in industrial effluents is presently limited by the national water law and a unique regulation limiting the Boron and Sodium content in detergents has been implemented. Israeli industry has undergone a radical change in recent years. Many factories and all the hospitals have adopted K or Ca for softening and neutralization, while others have shifted to reverse osmosis. The concentration of Cl and Na in the sewage reaching treatment plants is declining. The addition of Cl to sewage has dropped from 120 mg/l to 70 mg/l. The average Boron concentration in sewage has dropped from 0.6 mg/l to 0.3 mg/l and should reach 0.2 mg/l by 2008.