| Urban sewage treatment plant is one of the main sources of greenhouse gas emission from human activities.The existing accounting methods have large errors in the study of urban sewage treatment and discharge.This study improved the greenhouse gas accounting method and proposed the pollutant parameter normalizing method（PPNM）.The greenhouse gas emissions of 38 urban sewage treatment plants in Beijing in 2017 and 8 typical sewage treatment plants in Beijing from 2007 to 2021 were calculated by PPNM,and the regional greenhouse gas emission characteristics,time variation trend and influencing factors of Beijing were analyzed.According to the main influencing factors,corresponding emission reduction strategies are put forward.The main research conclusions are as follows:（1）In 2017,the greenhouse gas emissions from 38 urban sewage treatment plants in Beijing were 797,900 tons of CO2-eq,with indirect emissions accounting for 82%of the total,and the total emission intensity was 0.603 kg/m3.The discharge intensity of different wastewater treatment processes ranges from 0.075 to 0.277 kg CO2-eq/m3,and the direct discharge intensity of MBBR process is the highest,while OD process is the lowest.The indirect discharge intensity of sewage treatment decreases first and then increases with the treatment scale.When the treatment capacity is less than 5 million tons,5～10 million tons and 10～20 million tons,the power consumption of pollutant removal is 1.943,1.895,1.528 k Wh/kg COD and 28.772,14.457,10.323 k Wh/kg TN,respectively.（2）Greenhouse gas emissions from sewage treatment plants are affected by municipal construction,standard changes and operation optimization.From 2007 to2011,the improvement of sewage network resulted in the increase of total emission intensity from 0.19kg/m3 to 0.22 kg/m3,but the unit pollutant emission intensity decreased from 0.57 kg/kg COD to 0.52kg/kg COD.In 2012,the total greenhouse gas emission intensity increased to 0.37 kg/m3,and the unit pollutant emission intensity increased from 0.50 kg/kg COD to 0.71kg/kg COD.After 2017,the operation optimization of sewage treatment plants and energy utilization resulted in a decrease in the total greenhouse gas emission intensity of sewage treatment from 0.36kg/m3 to 0.31 kg/m3.（3）Sewage treatment plant can be mainly carried out from three aspects:treatment technology selection,energy utilization design and operation management optimization.At the same time,the optimization and formulation of sewage treatment standards also contribute to greenhouse gas emission reduction.According to the simulation results of different scenarios,greenhouse gas emissions from sewage treatment plants without emission reduction measures will increase by 132.9%in 2050.The combination of energy recovery and clean energy transformation can realize emission reduction of sewage treatment plants in advance,and relaxing the effluent standard of sewage treatment plants is a way of emission reduction with low economic input. |
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