Enhanced treatment performance and fouling mitigation in an algal-bacterial granular sludge-membrane bioreactor for liquor wastewater treatment.

Activated sludge-membrane bioreactors (AS-MBRs) are commonly used for liquor wastewater treatment; however, persistent membrane fouling and the challenging removal of refractory organics limit their long-term stability. In this study, simulated liquor wastewater was employed to compare an algal-bacterial granular sludge-membrane bioreactor (ABGS-MBR) with a conventional AS-MBR under different influent carbon conditions. ABGS-MBR achieved its best overall performance in Phase II (nominal C/N = 8), attaining COD, p-cresol, NH4±-N, TN, and PO43--P removals of 93.1 %, 82.1 %, 78.6 %, 65.7 %, and 70.0 %, respectively, together with slower transmembrane pressure development and lower filtration resistance. The improved performance was associated with the integrated characteristics of ABGS-MBR, including stable granular structure, greater microbial genetic potential, and favorable extracellular polymeric substances (EPS) and cake-layer characteristics. Specifically, ABGS-MBR exhibited higher relative abundances of taxa potentially associated with aromatic compound degradation and genes associated with carbon (e.g., glk, sdhC, and aceE), nitrogen (e.g., amoB, hao, and napB), and phosphorus (e.g., ppk1 and ppa) metabolism, indicating greater genetic potential for carbon, nitrogen, and phosphorus transformation. Meanwhile, lower accumulation of loosely bound proteinaceous EPS and weaker protein-like fluorescence were associated with a looser cake-layer structure. This study provides insights into the relationships among microbial genetic potential, EPS characteristics, and membrane fouling behavior in the integrated ABGS-MBR process under different influent carbon conditions for liquor wastewater treatment.