Denitrifying activity via nitrite and N ₂O production using acetate and swine wastewater

The presence of nitrite during denitrification is generally related to N ₂O emissions. The aim of this work was to determine the operational conditions that have influences in the specific denitrifying activities (SDA) and N ₂O production. Two factorial experimental designs (2 ³ and 2 ²) were performed to evaluate the effects of four operational variables (pH; biomass concentration; nitrite concentration and C/N ratio) on the SDA. Batch experiments were carried out with two different carbon sources: acetate and swine wastewater. Results showed that both biomass and NO ₂ ^- concentrations had a significant effect on the SDA in the presence of acetate, in the case of swine slurry, pH also affected the SDA. N ₂O production was only detected when swine wastewater was used and its specific production rate increased with the increase of the SDA. This result would indicate that N ₂O emissions are also promoted when swine wastewater is treated in conditions that favor the SDA.