Effect of micro-granular activated carbon on bacteriophage MS2 removal and fouling control in flat-plate MBR

Pathogenic microorganisms pose a severe risk to the aquatic environment and human health. Membrane bioreactors (MBRs) have attracted much attention due to their simultaneous biological treatment and virus retention, but membrane fouling is the main obstacle. This study explored the effect of micro-granular activated carbon (μGAC) on bacteriophage MS2 removal efficiency and membrane fouling in a flat-plate MBR. The results showed that the μGAC addition with a particle size of 180-300 μm improved the removal of MS2 (LRV_MBR of 4.77 log) and enhanced the removal of COD and ammonia nitrogen. The μGAC integrated MBR (μGAC-MBR) exhibited a higher MS2 retention rate by the membrane filter layers with an average LVR_Mem of 2.03 log compared to that of a control reactor (C-MBR) of 1.89 log. Meanwhile, the total membrane filter layer resistance of μGAC-MBR was significantly lower than that of C-MBR, particularly in terms of cake layer resistance and organic pore-blocking exclusion. The μGAC addition slightly reduced MS2 adsorption by the activated sludge while significantly altering the extracellular polymeric substances (EPS) profiles. The fluorescent components in the bound EPS and PN/PS ratio of the activated sludge were reduced. We found that μGAC enhanced membrane surface roughness and hydrophilicity. Notably, the μGAC significantly influenced the quorum sensing (QS) systems, reducing the abundance and synthesis of AHL-related genes. The synthase luxI in the AHL-QS system was reduced by 93.21% in μGAC-MBR. The AHL-QS system is closely related to biofilm formation, and the total EPS of the surface filer layer of μGAC-MBR decreased by 57.73%, and PN in LB-EPS and TB-EPS decreased by 91.33% and 54.44% compared with C-MBR, indicating a significant reduction in biofilm formation. This study exhibited a new perspective on promoting MS2 removal with the synergistic effect of alleviating fouling in the MBR process.