Influence of Temperature on Treatment Performance of Synthetic Sewage by Anaerobic Membrane Bioreactor (AnMBR)

Anaerobic membrane bioreactors (AnMBRs) in which anaerobic digestion and membrane separation are combined have recently been attracting attention, because they can recover methane and reduce sludge production in wastewater treatment. In this study, a laboratory-scale AnMBR for treating synthetic sewage was continuously operated with lowered the temperature gradually from 25 to 15°C to investigate the effect of temperature on the treatment performance, mass balance, and membrane performance. At hydraulic retention time (HRT) of 12 hours, the chemical organic demand (COD) concentration of the effluent and COD removal at 25, 20, and 15°C were 18, 17, and 40 mg•L-1 and 96, 96, and 92% respectively. Concerning the mass balance, no difference in the conversion ratios of methane including dissolved methane was seen, but the recovery ratio of methane gas at 15°C was about 10% lower than those at 25 and 20°C. Regarding the membrane performance, the rate of trans-membrane pressure was increased by lowering the temperature, and the reason increasing the membrane pressure was thought to be the blocking of pores by organic matter from microbial metabolic products. The AnMBR was expected to successfully produce clean water, recover energy efficiently, and reduce the amount of sludge produced compared with traditional sewage treatment.