Enhanced nitrogen removal and microbial synergy in a low-energy vibration-assisted membrane bioreactor for urban wastewater treatment

Membrane bioreactor (MBR) offers promising solutions for municipal wastewater treatment; however, challenges related to energy consumption and nitrogen removal efficiency persist. In this study, a low-energy partial nitrification MBR (LEP-N-MBR) system—including conventional aeration MBR (AMBR) and equipped with membrane vibration MBR (VMBR)—were evaluated during startup for pollutant removal performance, extracellular polymeric substances (EPS) dynamics, and microbial community structure. Both systems achieved high chemical oxygen demand (COD) and NH₄⁺-N removal, but the VMBR exhibited superior total nitrogen (TN) removal (54.7 %) compared to the AMBR (34.2 %) due to enhanced denitrification under vibration-induced anoxic conditions. EPS analysis revealed lower protein (PN) content in aerobic pools and increased polysaccharide (PS) accumulation in the MBR compartments, reflecting microbial adaptation and improved sludge floc stability. High-throughput sequencing showed shared enrichment of Proteobacteria and Bacteroidota, while VMBR fostered greater functional bacterial interactions and niche specialization, particularly among denitrifying genera. The novelty of this article lies in linking vibration-induced hydrodynamic conditions to enhanced denitrification through microbial niche specialization and EPS adaptation. This improves the nitrogen removal capacity of energy-efficient MBR systems, increases the potential for microbial resilience, and provides a basis for future large-scale process applications.