2022 Volume 58 Issue 2 Pages 71-81
Microplastics have received increasing attention as substances of potential risk due to their adverse effect on ecosystems and human health in recent year. Membrane bioreactors (MBRs) have excellent microplastic removal performance compared to conventional WWTPs. Meanwhile, there is a possibility that the membrane materials themselves become the source of microplastics when they deteriorate. Therefore, it is important to consider not only the antifouling performance for wastewater treatment but also the mechanical durability of the membranes to reduce microplastic production; thus, promoting application of MBRs. In this study, the mechanical durability and antifouling performance of three kinds of membranes, chlorinated polyvinyl chloride (CPVC), polytetrafluoroethylene (PTFE), and polyethersulfone (PES) used in a lab-scale submerged MBR for almost two months, was explored. The experiment was carried out in a lab-scale submerged MBR with effective working volume of 6.8 L. Synthetic wastewater was prepared with D-glucose, meat extract, polypeptone, and inorganic salts, and fed to the reactor. The mixed liquor suspended solids (MLSS) was constantly maintained within 11000-12500 mg/L. Significant breakage and rupture on the surface of the PES membrane and notable changes in the parameters such as pore size and surface roughness related to the membrane structure were observed through MBR operation. Contrarily, for the CPVC and PTFE membranes, only a slight change in the membrane structure and properties was observed. These results indicated that the PES membrane was more susceptible to damage by the shearing force with aeration for MBR than the other membranes. Therefore, the durability of the PES membrane was the lowest among the membranes studied, indicating high microplastic production risk, even though all three membranes have the same antifouling performance. This is the first report of changes in the membrane characteristics and morphology related to mechanical durability and the membrane fouling problem under MBR operation.
