A multi-pronged strategy towards one-stage partial nitritation/anammox in a lab-scale MABR

Membrane-aerated biofilm reactors (MABRs) incorporating partial nitritation and anammox (PN/A) can potentially intensify treatment capacity and achieve sustainable nitrogen removal in mainstream wastewater treatment. However, the undesired proliferation of nitrite-oxidizing bacteria (NOB) within biofilms remains a critical challenge for maintaining stable PN/A performance. Herein, a lab-scale MABR was operated for 280 days to achieve stable PN/A through a multi-pronged strategy combining preliminary inoculum selection, membrane aeration mode optimization and effective oxygen control safeguards. This strategy enabled stable and efficient PN/A performance, achieving an average total nitrogen removal efficiency of 91% and a high nitrogen removal rate of 180 mg N L^-1 d^-1. In-situ batch tests together with microbial community characterization revealed that ammonia-oxidizing bacteria (Nitrosomonas) and anammox bacteria ('Candidatus Brocadia') were enriched within the mature biofilm and cooperatively achieved efficient nitrogen removal, while the activity and abundance of NOB were effectively suppressed at low levels. Collectively, the findings provide insights into the application of PN/A in MABRs for intensifying mainstream wastewater treatment.