Performance investigation of membrane bioreactor systems during municipal wastewater reclamation.

Four commercially available membrane bioreactor (MBR) systems were operated at the pilot scale, to investigate performance during the reclamation of municipal wastewater. The MBR performance was evaluated under a variety of operating conditions, including two types of feed wastewater (raw and advanced primary effluent), hydraulic retention times (HRTs) ranging from 2 to 6 hours, and permeate fluxes between 20 and 41 lmh. Test results showed that MBR systems were capable of operating on advanced primary effluent, despite the possible presence of coagulant and/or polymer residual, with minimal membrane fouling. Membrane performance data generated during this study was also used to quantify the relationship between permeate flux and membrane fouling. Cleaning intervals at various flux conditions were estimated as follows: 69 days at 20 lmh, 58 days at 25 lmh, and 30 days for operation between 31 and 41 lmh. It was also demonstrated that the MBR process could be optimized to operate with minimal fouling under high hydraulic (flux = 37 lmh) and organic loading (HRT = 2 hours and food-to-microorganism ratio = 0.33 g COD/g VSS x d) conditions. Water quality monitoring conducted throughout the study showed that each MBR system consistently produced an oxidized (5-day biochemical oxygen demand < 2 mg/L) and nitrified (ammonia < 1 mg-N/L) effluent low in particulate matter (turbidity < 0.1 NTU), under all conditions tested.