Enhanced nitrogen removal and in situ microbial community in a two‐step feed oxic/anoxic/oxic‐membrane bioreactor (O/A/O‐MBR) process

Abstract

AbstractBACKGROUNDThe carbon in raw sewage can be reclaimed to reduce nitrate for the advanced denitrification in municipal wastewater treatment plants. A novel two‐step feed oxic/anoxic/oxic‐membrane bioreactor (O/A/O‐MBR) process was proposed to improve carbon‐use efficiency.RESULTSThe flow distribution ratio (FDR), aeration mode and hydraulic loading were optimized to minimize the effluent total nitrogen (TN) concentration. When the FDR was 1:1, the intermittent aeration mode was 4 min air‐on/6 min air‐off and the influent flow was 5 L h−1, the nitrate removal efficiency in the post‐denitrification tank rose to 87.0% and the effluent TN concentration decreased below 15.0 mg L−1. The intermittent aeration strategy in the post oxic‐membrane tank effectively promoted TN loss. The 15N‐DNA based stable isotope probing experiment illustrated that Proteobacteria (35.09%), Actinobacteria (20.56%) and Chloroflexi (16.67%) dominated the intermittently aerated biofilm, and Nitrospira (9.06%) was the major nitrite oxidizing bacteria rather than Nitrobacter, representing a dominant simultaneous nitrification and denitrification pathway for nitrogen removal.CONCLUSIONThe integration of autotrophic nitrifying bacteria and heterotrophic denitrifying bacteria enhances the terminal TN removal under intermittent aeration mode. The two‐step feed O/A/O‐MBR process has the potential to solve carbon limitation in sewage wastewater treatment. © 2018 Society of Chemical Industry