Effect of superficial gas velocity on membrane fouling behavior and evolution during municipal wastewater treatment

Abstract

Aerobic granular sludge membrane bioreactor (AGMBR) is a promising technology for wastewater reuse and membrane fouling mitigation. Superficial gas velocity (SGV) plays an important role in the efficient and stable operation of AGMBR. However, the effect of SGV on the membrane fouling behavior and evolution of AGMBR has not been reported, which was systematically investigated in this study. AGMBR with various SGVs was used to treat synthetic municipal wastewater, and more than 94.5% and 60.5% of organics and total nitrogen, respectively, were removed at all SGVs. Further, a larger SGV prolonged the AGMBR overall operation. Contents and physiochemical properties of foulants varied with SGV and transmembrane pressure (TMP). Micro-level analyses revealed that the proportion of pore-blocking resistance in total fouling resistance as well as the microbial community diversity in the sludge mixture or on the membrane surface increased with TMP and SGV. The correlation analyses demonstrated that decreasing the polysaccharide content of soluble microbial products, increasing the protein content of tight extracellular polymeric substances in the sludge mixture, and enhancing the relative abundance of Bacteroidia and Gammaproteobacteria were beneficial for mitigating membrane fouling. This study reveals membrane fouling evolution and provides theoretical guidance for the large-scale application of AGMBR in wastewater reuse.