Greenhouse Gas Emissions From Urban Wastewater Treatment Plants In Three Northeastern Provinces Accounting And Analysis Of Influencing Factors

Since the beginning of the 21st century,global warming has become increasingly serious,resulting in a series of serious problems,and controlling greenhouse gas emissions has become an important way to cope with global warming.The world is actively working to reduce greenhouse gas emissions and build a"green global village".Achieving the goal of low-carbon and green development requires the support of various industries.The greenhouse gases-carbon dioxide（CO₂）,methane（CH₄）and nitrous oxide（N₂O）-produced by urban wastewater treatment plants in the process of treating municipal wastewater are considered to be one of the important sources of greenhouse gas emissions,and low-carbon operation can reduce greenhouse gas emissions from urban wastewater treatment plants,which makes the urban wastewater treatment industry one of the industries with greater potential for emission reduction.In order to determine the characteristic GHG emission factors of urban wastewater treatment plants in the high latitude and low temperature areas of Northeast China,to provide guidance and suggestions for GHG emission reduction of urban wastewater treatment plants in Northeast China,and to overcome the bias of emission accounting caused by the traditional emission factor method which ignores the differences of emission factors of different treatment processes,this study takes urban wastewater treatment plants in three Northeastern provinces as the research object,and provides guidance and suggestions on the emission factors of different urban wastewater treatment processes.This study takes urban wastewater treatment plants in three northeastern provinces as the research object,and conducts relevant research on the construction of the factor system and accounting of greenhouse gas emissions from different urban wastewater treatment processes,the influence of process scale and loading rate of urban wastewater treatment plants on greenhouse gas emissions,and the analysis of regional differences in external influencing factors of carbon emissions,so as to provide a basis for achieving low-carbon development of urban wastewater treatment plants in northeast China and realizing the national low-carbon goal by 2030.Based on the compilation and analysis of the data on the construction scale,treatment process and operation conditions of urban wastewater treatment plants in the three northeastern provinces from 2015-2019,the emission factor method for different treatment processes is established.Based on the emission factor method of different wastewater treatment processes,the direct and indirect greenhouse gas emissions of all wastewater plants in the three northeastern provinces during 2015-2019 are accounted for,and the quantitative analysis of greenhouse gas emissions from urban wastewater treatment plants in the three northeastern provinces is realized.The analysis of the accounting results reveals that the greenhouse gas emissions from wastewater treatment plants in three northeastern provinces increased from 225,179,400 tons CO₂-eq in 2015to 28,961,800 tons CO₂-eq,an increase of 28.61%during the five-year period.Among them,Liaoning Province has the highest GHG emissions from wastewater treatment plants,which is about the sum of both Heilongjiang Province and Jilin Province.In terms of emission composition,indirect emissions account for the highest percentage in the whole Northeast region and are currently on a decreasing trend,with nitrous oxide emissions dominating the direct emissions.The emission structures of the three provinces differ significantly,with indirect emissions dominating in Heilongjiang and Liaoning provinces,while direct emissions dominate in Jilin province.The effects of wastewater treatment process,scale,and loading rate on GHGemissions from urban wastewater treatment plants were analyzed and found to have an effect on the intensity of GHG emissions.The results of the analysis found that the Anaerobic-Anoxic-Oxic（AAO）process contributed the most GHG emissions due to its most widespread use,and among the six processes the Sequencing Batch Reactor Activated Sludge Process（SBR）Among the six processes,Sequencing Batch Reactor Activated Sludge Process（SBR）has the highest emission intensity and Oxidation Ditch（OD）process has the lowest emission intensity.The GHG emissions and intensity of emissions vary greatly among WWTPs of different sizes,with larger WWTPs generally emitting more GHG,but larger WWTPs emitting less intensity.In terms of the loading rate of WWTPs,the intensity of methane and nitrous oxide emissions from direct emissions did not show significant differences with the change of loading rate,while the intensity of indirect emissions decreased continuously with the increase of loading rate.Using LMDI model to analyze the external influencing factors of greenhousegas emissions from wastewater treatment plants in three northeastern provinces,the results show that among the four influencing factors,the economic growth of the region has been an important influencing factor to promote greenhouse gas emissions,and the population size shows a suppressive effect,while the influence of wastewater production intensity and greenhouse gas emission intensity on the three provinces is not the same in the three provinces.