Role of membrane fouling layer in microbial fuel cell-membrane bioreactor (MFC-MBR) for controlling sulfamethoxazole and corresponding resistance genes.

Integrated MFC-MBR systems effectively remove antibiotics and control the release of antibiotic resistance genes (ARGs). However, the fouling layers on membranes can potentially act as reservoirs for ARGs. This study aims to elucidate the roles of membrane fouling layers and levels in influencing sulfamethoxazole (SMX) removal and ARGs control within an MFC-MBR system. Our findings demonstrate that low-intensity bioelectricity (400-500 mV) mitigates membrane fouling rates. The membrane fouling layer significantly contributes (39%-47%) to SMX removal compared to the cathode/anode zones. Higher extracellular polymeric substance (EPS) content and a lower protein/polysaccharide (PN/PS) ratio favor SMX removal by the membrane fouling layer. Across different levels of membrane fouling, the PN/PS ratio rather than EPS concentration plays a crucial role in SMX removal efficiency. The MFC-MBR with low fouling achieved superior SMX removal (69.1%) compared to medium (54.3%) and high fouling conditions (46.8%). The presence of ARGs in the membrane fouling layer increases with fouling formation, with intrinsic ARGs prevailing. Dense membrane fouling layers effectively retain ARGs, thereby reducing the risk of extracellular ARGs (eARGs) diffusion in effluents. These results provide insights into controlling ARGs in MFC-MBR systems and underscore the significant role of membrane fouling layers in antibiotics and ARGs removal.