Insight into biofouling mechanism in biofiltration-facilitated gravity-driven membrane (GDM) system: Beneficial effects of pre-deposited adsorbents

The membrane fouling triggered by biofouling layer is the critical factor limiting the application of biofiltration-facilitated gravity-driven membrane (GDM) system in decentralized drinking water treatment. Powdered acti-vated carbon (PAC) and alumina (AA) were used to mitigate membrane fouling by pre-deposition. Pre-deposited PAC and AA improved the stable flux of the biofiltration-facilitated GDM systems, increasing by 9.6% and 17.0%, respectively. The removal of dissolved organic carbon, UV254 and protein-like material was sequentially enhanced by pre-deposition of PAC and AA, respectively. Pre-deposited AA performed better than pre-deposition of PAC in restricting the adhesion of soluble microbial products to the membrane. After pre-deposition of PAC and AA, the porosities of the biofouling layers increased by 0.78% and 2.51%, and the protein/polysaccharide ratio in extracellular polymeric substances (EPS) decreased from 111.8% to 53.4% and 39.8%, respectively. The protein in tightly bound EPS showed a significant positive (p < 0.05) relationship with the total membrane resistance and genus Acidovorax. Zoogloea was the core genus among the bacterial communities related to EPS production. Overall, pre-deposition of PAC and AA can be a simple and effective strategy to alleviate membrane fouling in biofiltration-facilitated GDM.

Automated summary

Pre-deposition of powdered activated carbon (PAC) and alumina (AA) can effectively alleviate membrane fouling in biofiltration-facilitated gravity-driven membrane (GDM) systems. It improves the stable flux of the system and sequentially enhances the removal of dissolved organic carbon, UV254, and protein-like material. AA performs better than PAC in restricting the adhesion of soluble microbial products to the membrane and affects the porosity of the biofouling layer and the protein/polysaccharide ratio in extracellular polymeric substances (EPS).