Treatment of Municipal Wastewater in AnMBRs with PAC Addition Under Psychrophilic Temperatures.

The performance of anaerobic membrane bioreactors (AnMBRs) at psychrophilic temperatures commonly observed in temperate climates (10-24 degrees 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 degrees C and deteriorated at 10 degrees C. As temperature decreased, the COD mass flow to methane decreased and COD mass flows in the permeate and waste sludge increased. At 24 degrees C rapid membrane TMP increases were not observed while at 15 and 10 degrees C rapid increases occured at 11.7+/- 0.46 and 7.6+/- 0.45 days, respectively indicating a greater fouling propensity of the mixed liquor at lower temperatures. When the temperature was reduced from 15 degrees C to 10 degrees 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+/-0.46 days from 7.4+/-0.49 days. The primary benefit of PAC addition at low temperatures is enhanced membrane performance.