Effect of Influent COD/N Ratio on Nitrous Oxide Production during Denitrification Using Different Electron Acceptors

Nitrous oxide production in different influent COD/N ratios was investigated in lab-scale batch reactors using nitrite and nitrate as different electron acceptors, adding ethanol as external carbon source. The results showed that the maximum production of N2O was 1.91% (nitrite) and 0.48% (nitrate) of influent nitrogen, whereas 0.22% (nitrite) and 0.31% (nitrate) in the optimal influent COD/N ratio. Taking the effluent water quality and the minimum N2O production into account, the experiments suggested that the optimal influent COD/N ratio was 2.7-4.3 (nitrite) and 5.2-6.8 (nitrate). Furthermore, the results also demonstrated that the limited availability of electron donor resulted in nitrite accumulation which leaded to high N2O production. Hence, In order to reduce the production of N2O, it’s important to control influent COD/N ratio in an optimal value to avoid the accumulation of nitrite.