Pilot-scale anaerobic submerged membrane bioreactor (AnSMBR) treating municipal wastewater: the fouling phenomenon and long-term operation.

An anaerobic submerged membrane bioreactor (AnSMBR) on pilot-scale treating a mixture composed of municipal wastewater and glucose under mesophilic temperature conditions was operated for 206 days. The performance of the AnSMBR was evaluated at different fluxes, biomass concentrations and gas sparging velocities (GSV). GSV was used to control fouling. In addition, the AnSMBR was operated in cycles that included relaxation and backwashing phases. The increase in the transmembrane pressure (fouling rate) was measured under different operational conditions and was used to evaluate the stability of the process. The fouling rate could be controlled for a long period of time at a flux of 7 l m(-2) h(-1) with a GSV of 62 m/h and an average biomass concentration of 14.8 g TSS/L. The membrane was physically cleaned after 156 days of operation. The cleaning efficiency was almost 100% indicating that no irreversible fouling was developed inside the pores of the membrane. The COD removal efficiency was close to 90%. As in anaerobic processes, nutrients were not exposed to degradation and almost no pathogens were found in the effluent, hence the effluent could be used for irrigation in agriculture.