Groundwater recharge with municipal effluent: Dan Region Reclamation Project, Israel

Abstract

The Dan Region Project is the largest water reclamation scheme in Israel which provides for collection, treatment, groundwater recharge and reuse of municipal wastewater from Tel-Aviv metropolitan area and several other neighboring municipalities. The project serves a total population of about 1.3 million with an average municipal wastewater flow of 270,000 cu.m/d. The special recharge-recovery method developed and practiced successfully in the Dan Region Project is rather a soil aquifer treatment (SAT) which should be considered as an integral part of the municipal wastewater treatment process. SAT consists of controlled passage of effluent through the unsaturated zone and the aquifer, mainly for purification purposes, as well as for seasonal and multiannual storage. The recharge operation is carried out by means of spreading basins which are surrounding by adequately spaced recovery wells which permit separating the recharge zone from the rest of the aquifer. The major purification processes occurring in the soil aquifer system are: slow-sand filtration, chemical precipitation, adsorption, ion exchange, biological degradation, nitrification, denitrification and disinfection. Water quality control in the recharge zone is virtually complete and the very high quality of reclaimed water obtained after SAT is suitable for a variety of non potable uses especially for unrestricted agricultural irrigation. During the last five years, about 400 million cu.m of reclaimed water was supplied for unrestricted irrigation to the south of the country.