Management of biofilm by an innovative layer-structured membrane for membrane biofilm reactor (MBfR) to efficient methane oxidation coupled to denitrification (AME-D)

Methane oxidation coupled with denitrification (AME-D) has garnered significant attention as an economical technology for nitrogen removal from water. Effective biofilm management on the membrane surface is essential to enhance nitrate removal efficiency in AME-D systems. In this pioneering study, we introduce a novel and scalable layer-structured membrane (LSM) developed using a meticulously designed polyurethane sponge. This innovative application of LSMs in advancing biofilm management for AME-D has resulted in a substantial enhancement of denitrification performance. Experimental results demonstrated remarkable improvements in nitrate removal flux (92.8 mmol-N m-2 d-1) and methane oxidation rate (325.6 mmol m-2 d-1) when employing LSMs in membrane biofilm reactors (L-MBfR) compared to conventional membranes (C-MBfR). The L-MBfR exhibited a 12.4-fold rise in nitrate removal rate, a 6.8-fold increase in biomass retention capacity, and a 3.4-fold boost in methane oxidation rate in contrast to the control C-MBfR. Notably, the L-MBfR fostered a 3.5-fold higher abundance of denitrifying bacteria, including Xanthomonadaceae, Rhodocyclaceae and Methylophilaceae. Additionally, denitrification-related enzyme activity was twice as high in the L-MBfR compared to the C-MBfR. These findings underscore LSMs' ability to create anoxic/anaerobic microenvironments conducive to biofilm formation and denitrification. Furthermore, LSMs exhibited a unique advantage in shaping microbial community structures and facilitating cross-feeding interactions between denitrifying bacteria and aerobic methanotrophs. The results obtained in this study hold great promise for advancing the application of MBfRs in achieving efficient and reliable nitrate removal through the AME-D pathway, facilitated by effective biofilm management.