Virus removal during sewage treatment by anaerobic membrane bioreactor (AnMBR): The role of membrane fouling

Anaerobic membrane bioreactor (AnMBR) is a low-energy and promising solution for sewage treatment. During the treatment, the fouled membrane of AnMBR is recognized as an important barrier against pathogenic viruses. Here, the role of membrane fouling of an AnMBR at room temperature in the virus removal was investigated using MS2 bacteriophage as a virus surrogate. Results revealed that the virus removal efficiency of AnMBR was in the range of 0.2 to 3.6 logs, gradually increasing with the course of AnMBR operation. Virus removal efficiency was found to be significantly correlated with transmembrane pressure (R-2=0.92, p<0.01), especially in the rapid fouling stage, indicating that membrane fouling was the key factor in the virus removal. The proportion of virus decreased from 52.03% to 15.04% in the membrane foulants when membrane fouling was aggravating rapidly, yet increased from 0.74% to 21.52% in the mixed liquor. Meanwhile, the permeate flux dramatically dropped. These imply that the primary rejection mechanism of virus by membrane in the slow fouling stage is the virus adsorption onto membrane, while the sieving effect is the main reason in the rapid fouling stage. Ex-situ virus rejection test unveiled that the cake layer was the main contributor to the overall virus rejection, while the greatest resistance-specific virus rejection was provided by the organic pore blocking. This paper provides operation strategies to balance enhanced virus removal and high permeate flux by regulating the membrane fouling process.