Emission of N2O from a full-scale sequencing batch reactor wastewater treatment plant: Characteristics and influencing factors

N2O emission from a sequencing batch reactor (SBR) wastewater treatment plant (WWTP) was monitored through full-scale experiments to study the characteristics of N2O emission and the influence of environmental factors on N2O emission. Monitoring results indicated that N2O flux from different treatment units/periods followed a descending order: feeding period, aeration period, settling period, swirl grit tank, decanting period and wastewater distribution tank. N2O emission from this WWTP varied from 2.36 to 8.64 g (ton wastewater)−1 during the year. Feeding and aeration periods accounted for more than 99% of N2O emission in the WWTP. About 5.6% of N-influent was transformed into N2O and emitted, and nearly 120 ton of N2O would be emitted from this SBR WWTP in a whole year. The low DO concentration during nitrification was the major factor influencing N2O production. A lower water temperature or a lower influent COD/N might cause a higher N2O emission from the WWTP, but there was no positive correlation between the concentration of influent NH4+-N and N2O emission.