Production of N 2 O in two biologic nitrogen removal processes: a comparison between conventional and short-cut Nitrogen removal processes

The N2O production in two nitrogen removal processes treating domestic wastewater was investigated in laboratory-scale aerobic-anoxic sequencing batch reactors (SBRs). Results showed that N2O emission happened in the aerobic phase rather than in the anoxic phase. During the aerobic phase, the nitrogen conversion to N2O gas was 27.7%and 36.8% of NH 4 + -N loss for conventional biologic N-removal process and short-cut biologic N-removal process. The dissolved N2O was reduced to N2 in the anoxic denitrification phase. The N2O production rate increased with the increasing of nitrite concentration and ceased when NH 4 + -N oxidation was terminated. Higher nitrite accumulation resulted in higher N2O emission in the short-cut nitrogen removal process. Pulse-wise addition of 20 mg NO 2 − -N·L−1 gave rise to 3-fold of N2O emission in the conventional N-removal process, while little change happened with 20 mg NO 3 − -N·L−1 was added to SBR1.