AWWA MTC53731

Treatment of a surface water source for drinking water supply is a challenge onlyrecently undertaken by purveyors in the San Antonio, Texas area. San Antonioresidents have historically relied on groundwater sources, primarily the EdwardsAquifer, for drinking water supply. In 1996 however, the Bexar Metropolitan WaterDistrict (BMWD) initiated planning for San Antonio's first surface watertreatment plant drawing from the Medina River. In this paper, results from pilottesting of low-pressure membrane filtration on the Medina River water arereported. Clarification pretreatment and adsorption pretreatment were evaluatedduring pilot testing to determine the impact on operational membrane performanceand on removal of dissolved organic compounds including total organic carbon,UV254, color and precursors to disinfection byproducts. At the Medina Rivertesting site, clarification pretreatment was demonstrated to achieve greateroperating efficiency and significant removal of dissolved organics, as comparedto raw water treatment. These findings are compared with results from othermembrane pilot studies across the country to show that clarified feedwateroperation can achieve an apparent increase in sustainable flux between 25% and50% over raw feedwater operation. Includes 4 references, tables, figures.