The influence of trace NO2 on the kinetics of ammonia oxidation and the characteristics of nitrogen removal from wastewater

Ammonia oxidizing bacteria-enriched sludge was obtained in a sequencing batch reactor with synthetic wastewater. Batch tests of ammonia oxidation were carried out with the sludge, in the presence of only trace NO2 and in the presence of O-2 and trace NO2, respectively. The Andrews model is used to describe NO2-dependent ammonia oxidation. The maximum ammonia oxidation rate of 139.11mgN.(g sludgeCOD h)(-1), occurred in the presence of 21% O-2 and 100 ppm NO2, which was 3 times higher than the aerobic ammonia oxidation rate without NO2. The kinetic model of ammonia oxidation in the presence of O-2 and trace NO2 is developed, and the function of NO2 apparently enhancing ammonia oxidation is suggested. The maximal nitrogen removel of 34.19% occurred at the 21% O-2 and 100 ppm NO2 in the mixed gases. Nitrogen removal principally depended on the denitrification activity and NO2-dependent ammonia oxidation activity of ammonia-oxidizing bacteria (AOB).