Two-stage anoxic/oxic combined membrane bioreactor system for landfill leachate treatment: Pollutant removal performances and microbial community

In this study, a laboratory-scale two-stage anoxic/oxic (A/O) combined membrane bioreactor (MBR) was operated for 113 d for the treatment of landfill leachate. The average removal of chemical oxygen demand (COD), ammonia (NH4+-N) and total nitrogen (TN) achieved 80.60%, 99.04% and 74.87%, respectively. A mass balance evaluation suggested that the removal of COD, NH4+-N and TN occurred mainly in the second A/O process, and the total removal capacity of COD, NH4+-N and TN were 125.60 g/d, 24.35 g/d and 22.40 g/d, respectively. High-throughput sequencing analysis indicated that the Proteobacteria (44.57-50.36%), Bacteroidetes (22.09-27.25%), Planctomycetes (6.94-8.47%), Firmicutes (3.31-4.53%) and Chloroflexi (3.13-4.80%) were the dominated phyla in the bacterial community during the operation period. At the genus level, Nitrosomonas, Nitrobacter, Planctomyces, Saprospiraceae and Pseudomonas showed relatively high abundance, which played an important role in the removal of pollutants.