Membrane bioreactor (MBR) has attracted widespread attention owing to its unique membrane separation technology and high treatment efficiency. However, conventional MBRs struggle to remove pollutants with different oxygen requirements (e.g. nitrogen removal) in a single bioreactor, and the cost of membrane fouling control remains high. To address these challenges, this study devised an integrated gas-lift cross-flow Membrane Bioreactor (GL-CF-MBR), that possesses unique oxygen supply conditions and a cross-flow circulation pattern. Chemical analysis, 16S rRNA sequencing and transmembrane pressure (TMP) monitoring were employed to systematically evaluate the performance in terms of pollutant removal efficiency, microbial community composition and metabolic pathways, and membrane fouling behaviour. Results showed that the effluent concentrations of COD, NH₄⁺-N, and TN reached 25.58, 0.50, and 14.31 mg/L, respectively, meeting the Class 1A discharge standards of China's “Discharge standard of pollutants for municipal wastewater treatment plants’ (GB 18918-2002). Molecular biological analysis confirmed that, compared with the inoculated sludge, the Chao1 index and Observed species index increased by 37.32% and 30.94%, respectively. Moreover, denitrifying genera such as Rhodobacter and SC-I-84 were enriched in the system, and key functional genes involved in carbon and nitrogen metabolism were predicted. Owing to the unique flow field of the reactor, the time to reach a critical TMP surge for membrane modules installed in the scouring zone was delayed by 65.4% compared with those installed in the turbulent zone. The reactor promotes simultaneous pollutant removal and fouling mitigation, and its promising low operating cost provides a theoretical reference for practical engineering applications.
Ai et al. (Sun,) studied this question.