Simultaneous denitrification and phosphorus removal in MBfR with methane as the sole carbon source

Aerobic methane oxidation coupled to denitrification (AME-D) employed in membrane biofilm reactor (MBfR) is a promising strategy to reduce methane emission and enhance denitrification in wastewater treatment. However, focusing on enhancing nitrogen removal efficiency during AME-D has consistently overlooked the changes in phosphorus (P), and the underlying microbiome assembly mechanisms remain unclear. In this study, the MBfR was established to simultaneously enhance methane oxidation, denitrification, and P removal by the AME-D process under seasonal temperatures. The system achieved 72% of nitrate removal efficiency at 30 °C, while the P removal efficiency improved with the decrease of seasonal temperatures and stabilized at 86-99%. Microbiome analysis indicated that aerobic methanotrophs (Methylobacter), denitrifiers (Caenimonas), and denitrifying phosphorus-accumulating organisms (Gemmatimonas) were enriched in MBfR, facilitating the integrated removal of nitrogen and phosphorus alongside methane oxidation. The neutral community model (NCM) analysis revealed that microbiome assembly in MBfRs was driven by deterministic selection. Moreover, more network connectivity of the microbiome in MBfR biofilm suggested that membrane module enhanced the diversity and stability of microbiome. Our findings highlight the potential of AME-D with MBfRs as a robust and resilient platform for integrated greenhouse gas reduction and nutrient removal, offering practical implications for energy-efficient wastewater treatment.