Application of modified microbial flocculants in wastewater treatment process and mechanisms for membrane fouling mitigation

The application of pre-coagulation in the treatment of wastewater with bacterial-algal granular sludge membrane bioreactor (ABGMBR) and the mechanisms of membrane fouling mitigation were systematically investigated by using polymerized aluminum chloride (PAC) and modified microbial flocculant (MMF) as a composite flocculation system. Membrane filtration tests showed that PAC/MMF pre-coagulation effectively alleviated the membrane fouling compared with other flocculation systems. When the concentration of MMF was 20mg/L, the optimal flocculation capacity and membrane fouling control performance were achieved. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory clarified that the PAC/MMF system possessed superior antifouling properties. The PAC/MMF flocculation system greatly inhibited the adhesion and accumulation of foulants on the membrane, thus forming a loose, porous, and thin cake layer on the membrane surface. Correlation analysis showed that the mitigation of membrane fouling was mainly attributed to the decrease in the concentration of suspended solids and the increase in zeta potential in the raw wastewater. © 2023 Chinese Society for Environmental Sciences. All rights reserved.