Endogenous Nitrous Oxide Emission for Denitrifiers Acclimated with Different Organic Carbons

Nitrous oxide (N2O) emission occurs during denitrification, such as in biological wastewater treatments, but few studies have focused on N2O emission during denitrification under endogenous conditions. In the present study denitrifiers were acclimated with acetate or methanol as the electron donor, and endogenous denitrification kinetics including denitrification rates and N2O emission were examined in batch experiments for the acclimated denitrifiers. Oxidized nitrogen was denitrified slowly during endogenous respiration for denitrifiers acclimated with acetate or methanol, with the denitrification rate of lower than 2 mg/g VSS h. When the nitrate was used as electron acceptor, a low N2O emission ratio (lower than 1%) was obtained, while a high emission ratio (above 10%) was observed with nitrite as electron acceptor for both organic carbon acclimated denitrifiers. More attention should be paid to N2O emission during denitrification under endogenous conditions (such as in the settlement tanks) especially for systems with short-cut biological nitrogen removal through nitrite or systems with a high nitrite accumulation.