The membrane aerated biofilm reactor for nitrogen removal of wastewater treatment: Principles, performances, and nitrous oxide emissions

Nitrogen removal and nitrous oxide (N2O) emissions from biological wastewater treatment have been of considerable concern worldwide. Membrane aerated biofilm reactor (MABR) represents an innovative wastewater treatment technology that combines the advantages of the fixed-biofilm process and oxygen supply by membrane bubble-free aeration. Moreover, MABR has counter-diffusive electron transfer properties and unique microbial community stratification, which differs from that of conventional biofilms. Previous studies have explored and validated the advantages of MABR in wastewater treatment from laboratory to pilot-scale trials. Novel processes for nitrogen removal are being discovered and process modelling is being developed. This paper aimed to elaborate on the principle and characteristics of MABRs for nitrogen removal, particularly regarding novel microbial nitrogen removal processes. The study then reviewed the main influencing factors affecting nitrogen removal, including reactor design, operational conditions, N2O emissions as by-products, and mitigation measures. MABR may have broad application prospects for energy-efficient nitrogen removal, with challenges and opportunities for scaled-up applications. MABR has a lower potential for N2O emissions than conventional biological systems. Intermittent aeration and adjustment of biofilm homogeneity maximise nitrogen removal and minimise N2O emissions. Development of membrane materials with low-cost, versatile, high bio-affinity, high-breathability, and anticlogging properties is conducive to future large-scale application of MABR. Mathematical modelling was performed to optimise the operational parameters, and exploration of the available microbial community ecology is essential for nitrogen removal during MABR operation. This study provides a comprehensive prioritised theoretical reference for the development of MABRs for nitrogen removal.