N2O production during nitrogen removal in sequence batch reactor wastewater treatment systems

The nitrous oxide (N₂O) production from nitrogen removal process was studied in two laboratory sequence batch reactors (SBRs) using domestic and synthetic wastewater, respectively. Results showed that the total N₂O-N production reached 2.00 mg/L and 2.5% of influent total nitrogen (TN) was converted into N₂O. During the nitrification process, larger amount of N₂O was produced with the concentration of 1.97 mg/L, due to the fact that the coexistence of nitrite (NO₂^--N) and ammonia (NH4⁺-N) had stimulated the N₂O production. However, little N₂O was detected at the end of denitrification due to the higher N₂O reduction rate. The N₂O-N production during denitrification was only 0.03 mg/L. In addition, during the nitrification process N₂O concentration increased when the NO2^--N concentration was higher (≥1.0 mg/L), which showed that NO₂^--N was partially correlated with dissolved N₂O.