[Characteristics of simultaneous nitrification and denitrification in moving bed membrane bioreactor]

To investigate the removal efficiency of synthetic wastewater and characteristics of simultaneous nitrification and denitrification (SND) performances, a new type of moving bed membrane bioreactor (MBMBR) had been developed by using carriers instead of activated sludge in membrane bioreactor (MBR). Results showed that good organics removal and SND performances was achieved during the 67 d experimental period. COD, ammonium and total nitrogen removal efficiencies of MBMBR remained 88.3%-99.2%, 72.1%-99.8% and 62.0%-96.3% respectively as influent COD were 573.5-997.7 mg/L and ammonium nitrogen were 45.5-99.2 mg/L. Moreover, batch experiments results showed the optimum DO for nitrogen removal was 1 mg/L, ammonium and total nitrogen removal efficiencies were 100% and 60.0%, respectively. Aerobic denitrification may occur in biofilm system. When DO concentration was 3 mg/L and the organic carbon source was abundant, 99.0% total nitrogen removal efficiency and 99.8% SND efficiency was achieved in batch experiment. The microstructure of biofilm was examined using SEM. Results showed that some cavities were present, which would be favorable to enhance substrate and oxygen to transfer from the bulk to the interior of biofilm.