N2O production in a single stage nitritation/anammox MBBR process

found that when the added quantities of carbon source only allowed between 66-88%
denitrification, N2O emissions from the system were increased from an average of 0.2%
up to 1.3% of reduced nitrate. Long residence times for N2O in denitrifying sludge have
been shown to result in smaller amounts of emitted N2O. Since N2O is an intermediate in
the denitrification process dissolved N2O in the water phase can be turned over by the
denitrifiers and a long residence time for N2O increases the possibility that the gas is
converted into dinitrogen gas. The experiments showing these results were performed
in 100 ml bottles with different sludge volumes which also indicates that N2O emission
is greater from wastewater treatment basins with large surface to volume ratio
(Gejlsbjerg et al., 1997).
2.5.3 Chemical production of N2O
N2O can be produced by chemical denitrification in a wastewater treatment plant, the
reduction follows the same pathway as during biologic denitrification shown in eq.
(2.5.3). The difference is that chemical reductants are reducing the nitrogen compounds
instead of microbial enzymes (Debruyn et al., 1994).
Figures of N2O emissions from microbial nitrogen conversion found during the literature
study are summarised in Table 3.
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