Performance in full-scale MBRs treating domestic and industrial wastewaters and bacterial community structure dynamics

Membrane bioreactors (MBRs) are increasingly applied for domestic and industrial wastewater treatment. However, information linking treatment performance and microbial community dynamics in full-scale MBRs operating under tropical climate conditions remains limited. This study investigates bacterial community structures and treatment performance in four full-scale MBRs located in Thailand. The systems treated domestic wastewater and industrial process wastewater. Treatment performance and bacterial communities were evaluated using next generation sequencing. All MBRs operated stably under tropical conditions and complied with regulatory discharge standards. High BOD₅ removal efficiencies ranging from 85 to 99% were observed. TKN removal ranged from 62 to 94% depending on wastewater characteristics. The distinct bacterial community structures were identified among the systems. The core bacterial communities across all systems shared dominant phyla, including Proteobacteria, followed by Actinobacteria, Planctomycetes, Acidobacteria, Bacteroidetes, and Chloroflexi. However, some phyla, such as Gemmatimonadetes, Armatimonadetes, Verrucomicrobia, and Latescibacteria, were detected and attributed to differences in influent characteristics and pH conditions. Interestingly, the predominant bacterial genera under low pH condition were Mizugakibacter and Acidobacterium. Furthermore, the significant bacterial members which were responsible for TKN removal in domestic wastewater were Nitrosomonas and Nitrospira, whereas inindustrial wastewater were Candidatus Alysiosphaera and Haliangium. Overall, the results demonstrate that wastewater types driven pH variation strongly influence bacterial community dynamics in full-scale MBRs. This study provides field scale evidence and highlights the value of bacterial indicators for optimizing MBR performance and supporting non-potable water reuse.