Cake layer discrepancy triggered by different pore sizes in an anaerobic membrane bioreactor

Abstract

Cake layer formation is a key contributor to anaerobic membrane bioreactor (AnMBR) fouling. This study identified the discrepancy in the cake layer formation triggered by the pore size of the AnMBR. Five membrane modules with different pore sizes of 0.1, 0.22, 0.45, 1, and 5 μm were operated synchronously in the same AnMBR over a 120-day period. The transmembrane pressure (TMP) was observed and classified into three stages for each membrane. Pore size did not cause an obvious cake layer discrepancy at the initial stage, where the TMP increased. However, the membranes with larger pore sizes had a longer weak rise in the TMP during cake layer formation. The cake layer on the membranes with smaller pore sizes formed rapidly, but the cake layer on the membranes with bigger pore sizes could mitigate the TMP jump. The 0.45 μm membrane had the highest roughness and most severe cake layer formation. Acinetobacter showed obvious growth during cake layer formation, especially with a higher bacterial capacity on the membranes with smaller pore sizes. Pore size did not cause a genus-level discrepancy. However, there was a variation in bacterial percentage during cake layer formation.