AWWA WQTC64079

This study was conducted to determine if the use of membrane bioreactors (MBRs) may be feasible for the treatment of drinking water to control disinfection byproduct (DBP) formation. The study evaluated the removal of precursors in both groups of regulated organic DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs). In order to determine if it is possible for reactor biomass to be supported by the organic loading of a source water, a synthetic water made of powdered milk and micronutrients was used as the MBR influent. Fresh influent was made every 24-36 hours. The synthetic water was started at a chemical oxygen demand of 200 mg/L, which was equivalent to that of the feed into a local municipality's activated sludge tank. This corresponded to an initial total organic carbon (TOC) concentration of about 30 mg/L. The synthetic water influent concentration was lowered twice after a stabilization period ranging from a couple weeks to a couple months, to an influent TOC concentration of approximately 19 mg/L then to approximately 10 mg/L. The 10 mg/L concentration was starting to get close to the TOC range of a high TOC drinking water source. An immersed hollow fiber membrane bench scale reactor was constructed out of clear acrylic with a volume of 1.8 L. The membrane had an area of 0.03 m² and a porosity of 0.4 microns. The membrane flux was kept at approximately 0.45 m³/d/m². The reactor was seeded with activated sludge from the local wastewater treatment plant. Due to significant membrane fouling, powdered activated carbon (PAC) was also added after the first couple days at an initial concentration of 0.8 g/L. In order to determine the DBP precursor removal, effluent and influent were chlorinated and total trihalomethanes (TTHM) and the five regulated HAAs (HAA5) were analyzed after a 24 hour incubation period. The detailed experimental conditions have been reported by Stile (2006). Includes 4 references, table.