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 NO 2 and in the presence of O 2 and trace NO 2 , respectively. The Andrews model is used to describe NO 2 -dependent ammonia oxidation. The maximum ammonia oxidation rate of 139.11 mg N·(g sludge COD h) −1 , occurred in the presence of 21% O 2 and 100 ppm NO 2 , which was 3 times higher than the aerobic ammonia oxidation rate without NO 2 . The kinetic model of ammonia oxidation in the presence of O 2 and trace NO 2 is developed, and the function of NO 2 apparently enhancing ammonia oxidation is suggested. The maximal nitrogen removel of 34.19% occurred at the 21% O 2 and 100 ppm NO 2 in the mixed gases. Nitrogen removal principally depended on the denitrification activity and NO 2 -dependent ammonia oxidation activity of ammonia-oxidizing bacteria (AOB).