Membrane Fouling and Control Approaches in Membrane Bioreactor Systems: A Review

Membrane bioreactors (MBRs), in which membranes are performed to biological wastewater treatment for biomass separation, ensure many benefits over traditional wastewater treatment. The technology has developed to contain anaerobic MBRs (AnMBRs) due to the profit of generating renewable energy in the form of methane biogas and decreasing the cost of aeration and sludge disposal. Results show that the non-settleable substances and high solid concentrations in AnMBR cause to a significant membrane fouling inclination compared to aerobic MBR. Curiously, there seemed a critical AGS size (1-1.2 mm) for membrane fouling. Above or below critical AGS size, fouling declined as the size increase or decrease. Membrane fouling in MBRs can be reversible (i.e., detachable by physical washing) or irreversible (i.e., detachable by chemical cleaning solely), and can happen on the membrane surface or into the membrane pores. The use of air scouring (for aerobic MBRs) or biogas sparging (for AnMBRs) is widely used for fouling control. This paper provides to review current methods employed to mitigate and control membrane fouling in aerobic MBR, AnMBR and combined MBR systems. Overscale implementation of fouling control approaches should be the focus of future studies.