Nitrous oxide emissions from a typical northern Chinese municipal wastewater treatment plant

Nitrous oxide (N2O) emissions from a typical full-scale tertiary municipal wastewater treatment plant (WWTP) in northern China were investigated during spring and summer of 2010. Results showed that the major emission sources of N2O performed the following descending order: oxic tanks, final clarifier tanks, anoxic tanks, sludge concentration tanks and anaerobic tanks. The total annual N2O flux from the oxic tanks was the highest and accounted for the majority of total N2O emissions of this WWTP. The emission factors derived from the field measurements included per capita emissions of 1.73–2.19g of N2O person–1 y–1 and flow based emissions of 2.37×10–5–3.01×10–5 g of N2O (L of wastewater) –1. The N2O emissions accounted for approximately 0.10%–0.13% of the total nitrogen removed in this WWTP. The most significant factors influencing N2O emissions in this plant were dissolved oxygen concentration and nitrite concentration in the oxic tanks.