Wastewater Reclamation for Agricultural Reuse in Israel: Trends and Experimental Results

Abstract

Water shortage and a deterioration in the quality of water resources in Israel have made necessary a national policy recommending reuse of practically all municipal wastewater in order to supply a major part of agricultural water demand. Two pilot-scale systems were operated and studied for several years. The first one consisted of an advanced treatment scheme incorporating a sequencing batch reactor (SBR) system with further deep-bed granular filtration. The second system was an SBR unit, for the purpose of optimizing nitrogen and phosphorus removal and testing further microfiltration of SBR effluents. The SBR process has been shown to be an efficient biological treatment method producing low Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) effluents. SBR effluents, even if loaded with high TSS concentrations, could be further purified in the filtration stage, producing low-turbidity effluents. Granular filtration experiments were carried out using a gravitational single-medium filter composed of uniformly-sieved quartz sand. It was found that most of the suspended solids were removed in the top 10 cm of the filter bed. Influent turbidity was found to be the main parameter affecting the process, while filtration rate had only a minor effect. Microfiltration of SBR effluents showed highly efficient removal of turbidity and pathogens. Advanced mathematical models were developed and calibrated for both the biological process and for the granular filtration process.