Abstract:The effect of trace NO2 on the kinetic characteristics of coupling aerobic and anaerobic ammonium oxidation (ANAMMOX) in granular sludge was investigated by batch experiments. With trace NO2, aerobic ammonium oxidation process was enhanced by increasing the activity of O2, which was described by Andrews’s model. Half saturate coefficient and inhibition coefficient of NO2 were 1.32μmol/L and 7.11μmol/L, respectively. Anaerobic ammonium oxidation process was also enhanced by NO2. The maximum ANAMMOX enhancing coefficient was 43.5, while half saturate coefficient and inhibition coefficient of NO2 were 16.9μmol/L and 0.348μmol/L, the basic rate coefficient was 0.024 as well. Based on the kinetic analysis under trace NO2, completely autotrophic nitrogen removal process in an expanded granular sludge bed (EGSB) reactor was simulated. It was revealed that nitrogen removal efficiency reached the maximum when DO and NO2 were 0.6mg/L and 3.0μmol/L. Based on the stimulation, the operation of reactor was optimized. The nitrogen removal efficiency increased from 26.86%~31.65% to 58.83%~63.08%, as well as the removal rate increased from 0.113 kg/(m3·d) to 0.234kg/(m3·d).