Treatment of municipal wastewater in AnMBRs with powdered activated carbon addition under psychrophilic temperatures.

Abstract

The performance of anaerobic membrane bioreactors (AnMBRs) at psychrophilic temperatures commonly observed in temperate climates (10-24°C) was assessed. A unique aspect of the research was operation at controlled SRT with regular membrane cleaning. COD removal and permeate VFA concentrations were similar at 15 and 24°C and deteriorated at 10°C. As temperature decreased, the COD mass flow to methane decreased and COD mass flows in the permeate and waste sludge increased. At 24°C, rapid membrane TMP increases were not observed while at 15 and 10°C rapid increases occurred at 11.7±0.46 and 7.6±0.45days, respectively, indicating a greater fouling propensity of the mixed liquor at lower temperatures. When the temperature was reduced from 15°C to 10°C in a transient test, CH4 production was reduced and VFA concentrations increased. A 2-3 SRT lag in the responses suggested that the delayed response was due to long-term changes in microbial population. The permeate VFA content in a PAC-dosed reactor was lower than that without PAC dosing, and PAC addition increased the time to rapid TMP development to 11.3±0.46days from 7.4±0.49days. The primary benefit of PAC addition at low temperatures is enhanced membrane performance. PRACTITIONER POINTS: AnMBRs can produce high-quality effluents at temperatures of 15°C Membrane fouling increases as temperature decreases Bioreactor performance was sustained for 2-3 SRTs after temperature decrease PAC addition reduced the permeate VFA concentrations Membrane fouling at 10°C was reduced through PAC addition.