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.