Wastewater treatment industry, a top ten carbon emission source, has been significantly concerned in recent years. However, unclear system boundaries and undisclosed databases make it hard to estimate the greenhouse gas (GHG) emission from the wastewater treatment industry, especially in developing countries. Quantifying the total GHG emission characteristics at national level is helpful to identify the most emitted processes and propose suitable carbon mitigation strategies. This study accurately estimated the GHG emissions from Chinaâ€™s wastewater treatment industry by a model combined with operational data integrated methods and Intergovernmental Panel on Climate Change method. Then, the spatial distribution analysis and possible influential factors of total GHG emissions were further investigated by geographic model, Pearson correlation model and principal component analysis. Results showed that the national GHG emission from the total 4,205 wastewater treatment plants (WWTPs) in China in 2017 was 34.18 Mt CO2-eq, with 64.5% emitted from the consumption of electricity and chemicals. The GHG reduction strategies need to focus on process optimization and improvement at WWTPs, especially for the energy source shift, improved aeration, and on-site N2O emission from biological treatment process. After analyzing the spatial distribution characteristics, the total emission in the eastern region was approximately four times higher than that in the western region according to the Hu Line. Gross domestic product (GDP) and the treated volume of wastewater had strong positive correlations to the total GHG emissions in most first-tier cities, while there were no significant impacts on non-first-tier cities. Additionally, the impact of wastewater treatment scale on the discharge intensity is not significant, but the impact of technology is relatively obvious.
Keywords Wastewater treatment, GHG emission, operational data integrated methods, spatial distribution