中国污水处理厂甲烷排放研究

基于实测排放因子矩阵和排放源(污水处理厂)层面的活动水平,较为彻底地自下而上核算了中国2012年所有污水处理厂的CH4排放量.结果表明,中国污水处理厂总CH4排放为52642t,其中生活污水处理厂排放39921t,占75.84%,工业污水处理厂排放12721t,占24.16%.福建、江苏、浙江等省的CH4排放量最高,宁夏、青海、西藏等省的排放量最低.生活污水处理厂的CH4排放占主体,主要原因是全国生活污水处理厂去除的COD量远高于工业污水处理厂的去除量.全国仅福建和江苏两省的工业污水处理厂的CH4排放量超过了生活污水处理厂的排放量.相比国家信息通报2005年排放结果,本研究的结果比其低,主要是由活动水平和排放因子的差异造成.中国99.93%的城市污水处理厂年平均COD进口浓度都低于1000mg/L,85.94%的工业污水处理厂年平均COD进口浓度低于1000mg/L,导致厌氧工艺处理的COD量较少.中国污水处理厂去除掉的COD量仅是全国COD总去除量的小部分,而大多数(64.98%)的COD是在工业企业内部被去除掉的,而这部分废水的COD浓度较高,故企业内部的废水处理应该是污水处理部门主要的CH4排放源.此外,还有相当于全国COD产生量三分之一的COD排入自然环境,这一环节的排放因子研究较为缺乏.

Estimation of methane emissions of wastewater treatment plants in China

The CH4 emissions of each (domestic and industrial) wastewater treatment plants (WTP) in China in 2012 are estimated based on our field measured emission factors and detailed information of each WTP. The results show that the total emissions are 52642 tons, 39921 tons from domestic WTP and 12721 tons from industrial WTP, accounting for 75.84% and 24.16% of the total emissions respectively. Fujian, Jiangsu and Zhejiang are the top 3 emitters and Ningxia, Qinghai and Tibet are the lowest three emitters. The domestic WTP dominate the total emissions due to their high share of total COD treatment. The CH4emissions from industrial WTP are higher than that from domestic WTP only in Jiangsu and Fujian provinces. Compared with the CH4 emissions in 2005 reported in the Second National Communication on Climate Change of The People’s Republic of China, the result of this paper was lower than that due to the discrepancies of activity data and emission factors. It is estimated that 99.93% and 85.94% of annual entrance COD concentration of domestic WTP and industrial WTP respectively, are lower than 1000mg/L. The low annual entrance COD concentration leads to low use of anaerobic biological treatment. The COD removed in WTP only occupies a small part of total COD removed. A large part of removed COD (64.98%) is disposed by enterprises themselves. This part is probably the predominant source of CH4 emissions of wastewater treatment sectors in China, due to its huge volume of COD with high concentration. There is large quantity of COD released into nature, which is equivalent to one third of the COD generated in China. The emission factors research is far from sufficient in this field.