The use of a self-generated current in a coupled MFC-AnMBR system to alleviate membrane fouling

In this study, we developed a coupled microbial fuel cell-anaerobic membrane bioreactor (MFC-AnMBR) system to degrade and remove membrane foulants, rather than preventing foulants from reaching the membrane surface through electrostatic repulsion. The MFC-AnMBR system consists of a conductive membrane as the MFC anode and an MBR filter membrane. The operating time of an experimental group with a 0.38-mA current was extended to 89 days longer than that of a control group (no cleaning during the operating period). Fourier-transform infrared spectroscopy indicated that the main membrane foulants were polysaccharides, proteins, and lipids. The concentrations of polysaccharides and proteins were significantly lower in the experimental group than in the control group. In confocal laser scanning microscopy, membrane surface proteins, α-polysaccharides, and β-polysaccharides decreased in the experimental group by 45.34%, 57.19%, and 26.46% compared to the control group. Three-dimensional excitation–emission matrix fluorescence spectroscopy and molecular weight (MW) analysis revealed that foulants deposited on the anode film surface were degraded into substances with low MW more effectively in the experimental group than in the control group. Two-dimensional heterogeneous correlation spectroscopy and high-throughput sequencing revealed that protein-like substances were degraded in both the control and experimental groups, but degradation of polysaccharide-like substances was more efficient in the experimental group. The degradation of polysaccharide-like and protein-like substances can be attributed to bacteria involved in anaerobic fermentation and electrogenic bacteria. Therefore, in the presence of electrons, polysaccharide-like substances with high MW can be converted into hydroxy-containing compounds with low MW, which are more readily degraded and utilized by microorganisms, thereby preventing membrane fouling.