PERFORMANCE AND COST COMPARISON BETWEEN MF/RO AND EDR MEMBRANES FOR REDUCING THE SALINITY OF RECYCLED WATER

摘要

Tertiary-treated recycled water generated by wastewater treatment plants is typically comprised of relatively low chemical oxygen demand (COD) and total suspended solids (TSS), but the total dissolved solids (TDS) concentration in tertiary treated wastewater is always greater than that of the local potable water supplies. As communities transform drinking water to wastewater, significant levels of dissolved solids are added from a variety of sources (e.g. urine, soaps and detergents, industrial processes, etc.). Thus, when the TDS concentration in drinking water supplies increases (e.g. a greater reliance on imported water that has a higher TDS than local sources), the wastewater TDS concentrations inherently become elevated. In some areas that rely heavily on imported water (such as Southern California), the TDS concentration in the drinking water is already near the limits of acceptance for many users, so by the time the water is returned for recycling, TDS concentrations exceed these levels. In addition, as many water-scarce areas use more recycled water for applications that have return flows to the wastewater treatment plant (e.g. dual-plumbed systems that use recycled water for toilet flushing), dissolved solids will accumulate in the wastewater and lead to even higher TDS concentrations.