Start-up and synergistic nitrogen removal of partial nitrification and anoxic/aerobic denitrification in membrane aerated biofilm reactor

To reduce energy consumption and improve operational stability of traditional biological nitrogen removal (BNR) system, partial nitrification and anoxic/aerobic denitrification were synergistically implemented in membrane aerated biofilm reactor (MABR) by regulating DO and pH. The results indicated that the optimal DO, pH and C/N ratio were 1-2 mg/L, 9.0 and 4-7, respectively. The corresponding average organic removal rate (ORR), total nitrogen removal rate (TNRR) and nitrite accumulation rate (NAR) reached 324 gCOD・m-3・d-1, 48 gN・m-3・d-1 and 77.70%, respectively. Extracellular polymeric substance (EPS) content in biofilm was more abundant than that in inoculated sludge. Multiple aerobic denitrifiers were detected in the biofilm with the relative abundance of 11.19%-22.71%. AQUASIM simulation implied that the distribution and proportion of substrates and bacteria were significantly affected by DO and pH regulation. Overall, this study provided some important insights in the start-up and operation of synergistic nitrogen removal process in BNR system.