重新审视化粪池的温室效应:回顾与展望

REEXAMINING THE GREENHOUSE EFFECT OF SEPTIC TANK:EVIEW AND PROSPECTS

化粪池作为一种关键的初级污水处理设置单元,其因厌氧反应产生的大量甲烷(CH_(4))及部分氧化亚氮(N_(2)O)等温室气体,使其成为污水系统碳排放中的重要一环。目前许多研究都在因此呼吁逐步取缔化粪池,但鲜见深入且全面探讨化粪池的温室效应的研究。综述分析表明:化粪池产生的CH_(4)及N_(2)O均存在较大时空变异性,且N_(2)O实际排放情况仍待进一步考证;从全生命周期碳排放的视角来看,日常维护清掏产生的间接碳排放,以及取缔化粪池后对后续系统在碳排放方面产生的潜在影响仍值得深入探析。就具体温室气体排放能力而言,由于国内外化粪池功能定位不同等原因,国内测算值约为8.3 g CH_(4)/(cap·d),低于国外普遍的11.0 g CH_(4)/(cap·d)。就目前研究状况而言,估计核算类研究普遍存在参数不确定性较大,地区异质性强等问题,国内在实地监测类研究方面暂时“空白”,且在线监测的缺乏导致温室气体的时空变异性也并未得到细化描述。综上,亟待开展对中国地区化粪池的广泛监测与核算评估等工作,这将有助于指明未来化粪池的发展方向。

As a key primary wastewater treatment unit,septic tanks significantly contribute to the carbon emissions of wastewater systems due to the production of greenhouse gases,such as large amounts of methane(CH_(4))and some nitrous oxide(N_(2)O)from anaerobic reactions.Many studies are therefore calling for the phasing out of septic tanks,but few studies explore the greenhouse effect of septic tanks in-depth and comprehensively.In fact,a review of the greenhouse effect of septic tanks could help point the way to the future of septic tanks.The review shows that there is considerable spatial and temporal variability in both CH_(4) and N_(2)O emissions from septic tanks,and that the actual N_(2)O emissions need to be further verified;the indirect carbon emissions from routine maintenance and emptying and the potential impact of septic tank removal on subsequent systems in terms of carbon emissions are still worthy of further analysis,from an LCA carbon perspective.In terms of specific greenhouse gas emission capacity,due to the different functions of septic tanks in China and abroad,the domestic estimate is about 8.3 g CH_(4)/(cap·d),lower than the 11.0 g CH_(4)/(cap·d)commonly estimated abroad.Finally,in terms of the shortcomings of the current research,there are generally significant parameter uncertainties and regional heterogeneity in the estimation and accounting studies,and there is a temporary“gap”in the field monitoring studies in China,as well as a lack of online monitoring,resulting in the spatial and temporal variability of greenhouse gases not being described in detail.In this regard,there is an urgent need for extensive monitoring and accounting of septic tanks in China to clarify the phasing out of septic tanks.