A pilot scale anaerobic submerged membrane bioreactor (AnSMBR) with an external filtration unit for municipal wastewater treatment was operated for 100 days. Besides gas sparging, additional shear was created by circulating sludge to control membrane fouling. During the first 69 days, the reactor was operated under mesophilic temperature conditions. Afterwards, the temperature was gradually reduced to 20 degrees C. A slow and linear increase in the filtration resistance was observed under critical flux conditions (7 L/(m(2) h)) at 35 degrees C. However, an increase in the fouling rate probably linked to an accumulation of solids, a higher viscosity and soluble COD concentrations in the reactor was observed at 20 degrees C. The COD removal efficiency was close to 90% under both temperature ranges. Effluent COD and BOD(5) concentrations were lower than 80 and 25 mg/L, respectively. Pathogen indicator microorganisms (fecal coliforms bacteria) were reduced by log(10) 5. Hence, the effluent could be used for irrigation purposes in agriculture. (C) 2011 Elsevier Ltd. All rights reserved.