Nitrous oxide (N2O) is one of the three main greenhouse gases (CO2

CH4

N2O)

about 265 times more effective than carbon dioxide (CO2)

and it may also destruct the ozone layer. In wastewater biological nitrogen removal process

autotrophic nitrification has been thought to be the major source of N2O production. In this study

by testing the production of N2O under different conditions

the relationship between N2O production rate and ammonia oxidation rate during nitritation process was investigated in a laboratory batch-scale system with activated sludge for treating domestic wastewater. The experimental data indicated that the ammonia oxidation rate (AOR) increased with higher DO while N2O production rate (N2OR) increased first then decreased. Besides the AOR and N2OR were by varying the initial ammonium (NH4+-N) concentration in batch experiments. The max N2OR was 1.29 mg N2O·(g MLVSS)-1·h-1 when DO was 0.6 mg·L-1. At low DO level

the increase of AOR would promote the N2OR. On the other hand

higher AOR might not produce more N2O when DO was high. There were different pathways of N2O production under various conditions which led to the change of N2OR. When DO was low

N2O was mainly produced by nitrosyl radical (NOH)

while increasing AOR promoted the N2OR formation. However

nitrifier denitrification by AOB was the main way of producing N2O at high DO level. This pathway might be inhibited by high DO

and thus even there was high AOR

the net production of N2O was still less. In addition

the existence of was very important to N2O production too.