Impact of different factors on greenhouse gas generation by wastewater treatment plants in China

Wastewater treatment plants (WWTPs) emit greenhouse gas (GHG), which may lead to climate change and global warming effect. During recent years, the increase of the number of WWTPs in China has made the study of the GHG emissions from WWTPs extremely important. This paper presents a complete estimation procedure of GHG generation by considering direct GHG emissions, indirect emissions from energy consumption and some other optional emissions. Based on the system, the overall GHG emissions of nearly 2000 WWTPs in China in 2009 were simulated and analyzed. Generally, the result indicated that the emission factor is about 4.23 kg CO2/kg COD. Furthermore, impact of different factors, such as treatment processes, distribution regions, plant scales, operational load rate and month, were compared. On this basis, recommendations were proposed for GHG emission reduction.