Biodegradation of phenolic compounds in high saline wastewater by biofilms adhering on aerated membranes.

High saline phenolic wastewater is a typical toxic and refractory industrial wastewater. A single membrane-aerated biofilm reactor (MABR) was used to treat wastewater containing phenol, p-nitrophenol and hydroquinone under increasing phenolic loading and salinity conditions. More than 95 % of phenolic compounds were removed, and a removal efficiency of 8.9 g/m d for total phenolic (TP) contents was achieved under conditions with 32 g/L of salt and 763 mg/L of influent TP contents. The microbial diversity, structure and function of a biofilm exposed to different conditions were investigated by high-throughput 16S rRNA gene sequencing and metagenomics. Salinity and specific TP loading substantially affected the bacterial community. Gammaproteobacteria, Actinobacteria and Betaproteobacteria contributed more to initial phenolic compound degradation than other classes, with Pseudomonas and Rhodococcus as the main contributing genera. The key phenolic-degrading genes of different metabolic pathways were explored, and their relative abundance was strengthened with increasing phenolic loading and salinity. The diverse cooperation and competition patterns of these microorganisms further promoted the high removal efficiency of multiple phenolic contaminants in the biofilms. These results demonstrate the feasibility of MABR for degrading multiple phenolic compounds in high saline wastewater.