Ammonium is oxidized to nitrate under aerobic conditions
:NH + 2O → NO + HO  + 2H
Ammonium oxidation can be treated as part of BOD, so that BOD = CBOD + NBOD, where CBOD is the carbonaceous biochemical oxygen demand and NBOD is nitrogenous BOD. Usually CBOD is much higher than the ammonium concentration and thus NBOD often does not need to be considered. The change in oxygen deficit due to oxidation of ammonium is described as
where
* D is the saturation deficit.
* is the nitrification rate .
* is ammonium-nitrogen concentration.
The range of  is typically 0.05-0.5 .