Characteristics of nitrogen removal and nitrous oxide production in CANON process

BACKGROUND Ammonia ( NH 3 ) was converted to dinitrogen gas ( N 2 ) cooperating between ammonia‐oxidizing bacteria ( AOB ) and anaerobic ammonia‐oxidizing bacteria ( AnAOB ) with low amounts of nitrous oxide ( N 2 O ) as the side‐product in the completely autotrophic nitrogen removal over nitrite ( CANON ) process. Contributions of anaerobic ammonia oxidation (anammox) by AnAOB and nitrifer denitrification by AOB for nitrogen (N) removal and the characteristics of N 2 O production were investigated comprehensively in this study . RESULTS AnAOB was the dominant contributor to autotrophic nitrogen removal, and the contributions from nitrifier denitrification were less than 13.55% of the N removal. Nitrite ( NO 2 ‐ ) addition increased the N removal rate of the CANON process under oxygen limiting conditions; N 2 O primarily produced from nitrifier denitrification by AOB was 0.41–7.25% of the N removal, and there was a positive correlation between NO 2 ‐ concentration and N 2 O production. Under anaerobic conditions, 10 mmol L −1 methanol did not completely inhibit the activity of AnAOB , but N 2 O production rate was significantly decreased with the addition of methanol . CONCLUSION The contribution from nitrifier denitrification by AOB was less than 13.55% of the N removal, and AnAOB played an impotent role in N 2 O production by providing hydroxylamine as an electron donor for AOB to reduce NO 2 ‐ in the CANON process. © 2013 Society of Chemical Industry