A novel three-dimensional biofilm-electrode/anoxic-oxic process for nitrogen and phosphorus removal: Performance, mechanism and microbial community

Traditional anoxic-oxic (AO) process cannot meet increasingly high pollutants emission standards in China. In order to improve removal efficiencies of the pollutants and the electron transfer rate, graphite-graphite electrodes and iron carbon fillers were added into AO reactor to form three-dimensional biofilm electrode/anoxic aerobic reactor (3DBER/AO). Removal efficiencies of the pollutants, sludge properties and microbial community structure were investigated under different current intensities. The results showed that microbial activity and removal efficiencies of the pollutants were the maximum, and mass percentage of Fe reached the highest value of 5.11 % under the current of 40 mA. Excessive or insufficient current intensity could lead to a decrease in sludge activity and removal efficiencies of the pollutants. The removal of nitrogen mainly depended on the nitrification and denitrification of microorganisms, and dissolved phosphorus was removed through chemical precipitation. Current intensity affected microbial communities and biosynthesis. AKYH767 and Saccharmonadales were dominant microorganisms in the cathode and anode sludge, respectively, under the current of 40 mA. However, Azospira and Dechlorobacter were dominant microorganisms in the cathode sludge, and Hydrogenophaga was dominant microorganisms in the anode sludge under the current of 60 mA. These microorganisms were closely related to the removal of organic matter, nitrogen and phosphorus. Therefore, microbial community structure and removal efficiencies of the pollutants could be regulated by controlling the current intensity in the 3DBER/AO process.