Important effects of temperature on treating real municipal wastewater by a submerged anaerobic membrane bioreactor: Removal efficiency, biogas, and microbial community

[Display omitted] •Real municipal wastewater was treated at 15–25 °C by a SAnMBR at HRT 6 h.•COD removal efficiencies of 90% and BOD removal efficiencies of 92% were obtained.•Electric energy could generate 2.27 kWh/d from biogas in a 10000 m3/d plant.•Trans-membrane pressure and fouling risks were high under the low temperature.•Populations of functional microbes had significant relations with the temperature. A submerged anaerobic membrane bioreactor (SAnMBR) was used in the treatment of real municipal wastewater at operation temperatures ranging from 15 °C to 25 °C and hydraulic retention time (HRT) of 6 h. The treatment process was evaluated in terms of organic removal efficiency, biogas production, sludge growth and membrane filtration. During long-term operation, the SAnMBR achieved chemical oxygen demand removal efficiencies of about 90% with a low sludge yield (0.12–0.19 g-VSS/g-CODrem) at 20–25 °C. Approximately 1.82–2.27 kWh/d of electric energy was generated during the wastewater treatment process at 20–25 °C, 0.67 kWh/d was generated at 15 °C. The microbial community analysis results showed that microbial community was dominated by aceticlastic methanogens, coupled by hydrogenotrophic methanogens and a very small quantity of methylotrophic methanogens. It was also shown that the stabilization of the microbial community could be attributed to the carbohydrate-protein degrading bacteria and the carbohydrate degrading bacteria.