Methane emissions from a full-scale A/A/O wastewater treatment plant

Methane (CH4) emissions from a full-scale anaerobic/anoxic/oxic (A/A/O) wastewater treatment plant (WWTP) (Jinan, China) were investigated during spring and summer of 2010. Results showed that the major emission sources of CH4 performed the following descending order: anaerobic tanks, oxic tanks, aerated grit chambers and sludge concentration tanks. The total annual fluxes of CH4 emissions from the Jinan WWTP were 1.69 × 104 kg yr−1, with the emission factors of per capita emissions of 11.3 g CH4 person−1 yr−1 and flow-based emissions of 1.55 × 10−4 g CH4 (L of wastewater)−1. The estimated source strength of methane for all WWTPs in China was 6.2 Gg yr−1 (1 Gg = 109 g). The most significant factors influencing methane emissions were dissolved oxygen concentration in aerated grit chamber and oxic tank and water temperature in high density settler tanks.