Department of Civil and Environmental Engineering, University of California, Davis, California 95616, United States.
Environ Sci Technol. 2011 Apr 1;45(7):2741-7. doi: 10.1021/es1036095. Epub 2011 Mar 7.
Emissions of CH4, CO2, and N2O from conventional septic tank systems are known to occur, but there is a dearth of information as to the extent. Mass emission rates of CH4, CO2, and N2O, as measured with a modified flux chamber approach in eight septic tank systems, were determined to be 11, 33.3, and 0.005 g capita(-1) day(-1), respectively, in this research. Existing greenhouse gas (GHG) emission models based on BOD (biochemical oxygen demand) loading have estimated methane emissions to be as high as 27.1 g CH4 capita(-1) day(-1), more than twice the value measured in our study, and concluded that septic tanks are potentially significant sources of GHGs due to the large number of systems currently in use. Based on the measured CH4 emission value, a revised CH4 conversion factor of 0.22 (compared to 0.5) for use in the emissions models is suggested. Emission rates of CH4, CO2, and N2O were also determined from measurements of gas concentrations and flow rates in the septic vent system and were found to be 10.7, 335, and 0.2 g capita(-1)day(-1), respectively. The excellent agreement in the CH4 emission rates between the flux chamber and the vent values indicates the dominant CH4 source is the septic tank.
传统化粪池系统会排放 CH4、CO2 和 N2O 等温室气体，但目前对此类排放的程度还缺乏了解。在这项研究中，采用改良的通量室方法，在八个化粪池系统中测定了 CH4、CO2 和 N2O 的质量排放率，分别为 11、33.3 和 0.005 g 人(-1)天(-1)。基于 BOD（生化需氧量）负荷的现有温室气体（GHG）排放模型估计甲烷排放量高达 27.1 g CH4 人(-1)天(-1)，是我们研究中测量值的两倍多，并且得出结论认为，由于目前有大量的化粪池系统在使用，化粪池可能是 GHG 的重要来源。基于测量的 CH4 排放值，建议在排放模型中使用修正后的 CH4 转换系数 0.22（相比之下为 0.5）。通过测量化粪池通风系统中的气体浓度和流量，还确定了 CH4、CO2 和 N2O 的排放率，分别为 10.7、335 和 0.2 g 人(-1)天(-1)。通量室和通风值的 CH4 排放率非常吻合，表明主要的 CH4 来源是化粪池。
