Long-term operational performance and membrane fouling mechanisms of AGMBR treating municipal wastewater under different superficial air velocities

Abstract

The granulation and stability of aerobic granular sludge (AGS) as well as membrane fouling in AGS-membrane bioreactor (AGMBR) are significantly influenced by superficial air velocity (SAV). However, there is a lack of relevant research on this topic. Therefore, this study aims to investigate the specific impacts of SAV on AGMBR performance and membrane fouling. The results showed that the experimental SAVs (1.6, 2.1, and 2.6 cm/s) were found to provide sufficient dissolved oxygen for the removal of organics and ammonium nitrogen at efficiencies exceeding 94.50% and 99.40%, respectively. The larger SAV also extended the overall lifespan of the AGMBR, while altering both the content of foulants on fouled membranes and their associated microbial community structure. Moreover, the cake layer exhibiting the highest degree of porosity was observed at an SAV of 2.6 cm/s, which corresponded to the largest pore blocking fouling resistance (28.81% of the total fouling resistance) and the presence of fluorine on the fouled membrane. Additionally, the results from extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory were consistent with the increase in transmembrane pressure. Polysaccharides (PS) played a more significant role than proteins in membrane fouling, and the PS present in soluble microbial products exhibited a strong correlation with fouling resistance distribution. This study aims to optimize the treatment performance and minimize membrane fouling in AGMBR, thereby establishing a mutually beneficial scenario that is essential for the practical implementation of wastewater reuse in engineering.