推进污水处理过程碳减排对于实现碳达峰、碳中和 目标具有重要意义.垃圾焚烧渗沥液成分复杂、污染物浓度高,其处理系统是温室气体的重要排放源之一.然而,目前渗沥液处理系统碳排放特性尚不清晰,这阻碍了减污降碳方案制定与实施步伐.以长三角地区某典型生活垃圾焚烧发电厂渗沥液处理系统为研究对象,采用生命周期评价方法(life cycle assessment,LCA)对其进行碳足迹核算,重点关注其在不同水质、水量条件下的碳排放特性并评估其减污降碳潜力.结果表明:渗沥液处理系统的直接碳排放量呈春夏高、秋冬低的趋势,其中,N2O是最重要的直接碳排放来源(0.4～47.7 t CO2 eq);间接碳排放量远高于直接碳排放量,电力是最大的间接碳排放来源(78.2～121.3 t CO2 eq).虽然外加碳源可在一定程度上减少直接碳排放量,但会增加间接碳排放量.回收厌氧消化(anaerobic digestion,AD)单元中产生的CH4(0～160.3 t CO2 eq)是实现渗沥液处理系统碳中和重要途径.垃圾分类后虽然直接和间接碳排放量有所降低,但碳回收量有限,使得渗沥液处理厂净碳排放量增加,渗沥液处理系统从碳汇转变为碳源.总体来说,在渗沥液处理系统碳减排策略中,电力是需要重点控制的碳排放来源,可通过提高脱氮效果来减少直接碳排放量.在各渗沥液处理单元中,两级硝化反硝化(A/O)工艺的升级改进至关重要,可有效实现节能减排.
RESEARCH ON CARBON EMISSION CHARACTERISTICS OF MUNICIPAL SOLID WASTE INCINERATION LEACHATE TREATMENT SYSTEM
The composition of leachate from municipal solid waste(MSW)incineration is complex and has high concentrations of pollutants,making its treatment system an important source of greenhouse gas emissions.However,the carbon emission characteristics of the incineration leachate treatment system are still not clear,which hinders the development and implementation of pollution reduction and carbon reduction strategies.Therefore,in this study,the inclination leachate from a typical MSW incineration plant in Shanghai was selected as the research object.The carbon footprint of the incineration leachate treatment system was calculated using a life cycle assessment method.The study focused on the carbon emission characteristics of the leachate treatment system under different water quality and quantity conditions.The carbon emissions of different treatment units were quantitatively analyzed to provide a scientific basis for upgrading and transforming low-carbon treatment processes for incineration leachate and achieving coordinated pollution reduction and carbon reduction goals in China.The results showed that direct carbon emissions tended to be higher in spring and summer and lower in autumn and winter,with N2O being the most important direct carbon emission source(0.4～47.7 t CO2 eq);indirect carbon emissions were much higher than direct carbon emissions,with electricity being the largest source of carbon emissions(78.2～121.3 t CO2 eq).In addition,external carbon sources could reduce direct carbon emissions to some extent but would increase indirect carbon emissions.Recovering CH4 generated in the anaerobic digestion(AD)unit(0～160.3 t CO2 eq)is an important pathway for achieving carbon neutrality in the leachate treatment system.Although the direct and indirect carbon emissions were reduced after waste classification,the limited carbon recovery led to an increase in net carbon emissions from the leachate treatment plant,causing the leachate treatment system a transition from a carbon sink to a carbon source.Overall,in the carbon reduction strategy for the incineration leachate treatment system,it is crucial to focus on controlling carbon emissions from electricity.Reducing direct carbon emissions can be achieved by improving denitrification efficiency.Upgrading and improving the two-stage anoxic/oxic(A/O)process in each leachate treatment unit is essential for achieving energy savings and emissions reduction.
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