Formation of membrane fouling and removal mechanism of contaminants in osmotic microbial fuel cells in the presence of perfluoroalkyl substances.

The osmotic microbial fuel cell (OsMFC) is an innovative wastewater treatment technology that integrates electricity generation with clean water extraction. OsMFC has the potential to treat industrial wastewater. However, membrane fouling poses a significant challenge to the practical application of OsMFC. This study examines the effect of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) on membrane fouling in OsMFCs. After long-term operation, it was found that the presence of PFAS reduced the water flux of OsMFC and aggravated the membrane fouling. Exposure to PFAS resulted in poor surface hydrophilicity. The membrane fouling was composed of α-D-glucopyranose, β-D-glucopyranose, proteins, and cells. Under PFOA exposure conditions, membrane fouling of OsMFC mainly occurred at the initial stage of operation. While PFOS existed, membrane fouling developed slowly. Further, the membrane cleaning methods and their effects were investigated. Among them, physical cleaning can achieve an ideal water flux recovery rate (up to 95 %). Further, to solve the problem that the removal rate of PFOA and PFOS was not ideal, more than 60 % of PFOA and PFOS were removed by optimizing the hydraulic retention time. Finally, the distribution and fate of PFOA and PFOS in OsMFC were determined. Adsorption removal by biofilm was the main way of their removal. This study provides a reference for the sustainable operation of membrane reactors in the presence of PFAS and the optimization of the biological removal process of PFAS in wastewater.