Assessing the performance and microbial structure of biofilms in membrane aerated biofilm reactor for high p-nitrophenol concentration treatment

P-nitrophenol (PNP) is a mono-nitrophenol compound that is highly toxic and difficult to degrade, causing great harm to the ecological environment and human health. In this study, a membrane aerated biofilm reactor (MABR) was used to degrade high PNP concentration without external carbon sources. This experiment mainly presented the process performance of MABR under high-load shock of PNP and variations in the community biodiversity and compositions of MABR biofilm. The experimental results showed that as the concentration of PNP in the influent gradually increased from 100 mg/L to 400 mg/L, the MABR exhibited a strong shockproof ability. The performance of the MABR peaked at an influent PNP concentration of 200 ± 50 mg/L, the removal efficiencies of PNP and chemical oxygen demand (COD) were 94.40% and 79.57%, respectively, and the removal loads were 3.644 g·m−2·d−1 and 4.975 g·m−2·d−1, respectively. The results of high-throughput sequencing revealed that MABR biofilms had high microbial richness and diversity, in which the microbial activity was not influenced by high-load shock. PNP, as a selective pressure, was used by microorganisms as the sole carbon source. The relative abundance of dominant phyla (Patescibacteria, Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota), classes (Saccharimonadia, Clostridia, Actinobacteria, Bacilli, Gammaproteobacteria, Bacteroidia, and CPR2), and genera (TM7a, unclassified_o_Saccharimonadales, Proteiniclasticum, and norank_f_norank_o_Saccharimonadales) were different between the evaluated samples. Numerous candidate phyla radiation (CPR) bacteria were enriched in the MABR, indicating that CPR was the functional bacteria responsible for the degradation of high concentrations of PNP. The findings of this study demonstrated that the MABR system possesses great feasibility and potential for the advanced treatment of phenolic compounds. [Display omitted] •A MABR was set up to degrade high PNP concentration without external carbon sources.•The best threshold concentration of the MABR was determined.•The microbial variations in the MABR biofilm were investigated.•CPR was the functional bacteria for the degradation of high concentration PNP.•MABR possesses great potential for advanced treatment of phenolic compounds.