Selecting aeration in a PVDF flat-sheet membrane bioreactor for municipal wastewater treatment

Membrane bioreactors (MBRs), which have been widely used in wastewater treatment and reuse, are restricted by membrane fouling and high energy consumption. This study examines the influences of aeration mode and flow rate on membrane fouling to present recommendations for selecting aeration in polyvinylidene fluoride flat-sheet MBR. Results show that continuous aeration (CA) at a constant flow rate can effectively alleviate membrane fouling, although relaxation stage aeration significantly affects the removal of the cake layer. In the short term, increasing the flow rate of CA effectively controls the deposition of suspended solids and alleviates membrane fouling. However, increasing flow rate exerts high shear stress on microbial flocs, thereby reducing microbial size and causing breakage/deflocculation of sludge flocs in the long term. The results indicate that a high flow rate affects sludge properties and the main fouling contributor changes from suspended solids to colloids. Moreover, the threshold ammonia (NH4+-N) concentrations of the supernatant and the effluent reveal that removing ammonia can optimize the flow rate of CA.