N2O and NO emissions during wastewater denitrification step: Influence of temperature on the biological process

The denitrification process occurring in wastewater treatment plants (WWTPs) is responsible for nitrous oxide (N2O) and nitric oxide (NO) emissions. These compounds indirectly lead to the global warming. In this study, we investigated the impact of the temperature on N2O and NO emissions. Experiments were achieved at PH 7 in a batch reactor with acetate as the carbon source. The nitrogen source was nitrates (NO3-) and the COD/N ratio was set to three. Results showed that NO and N2O emissions increased when the temperature decreased. NO emissions appeared only at 10 degrees C and 5 degrees C, with respectively 8% and 18% of the total denitrified nitrogen. N2O emissions increased from 13 to 40 then 82% of the total denitrified nitrogen, respectively at 20, 10 and 5 degrees C. Several hypotheses were suggested to explain these results: a general enzymatic slow down, enzymatic inhibitions, electron donor competition between the different enzymes and metabolic pathway alterations. (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.