A/O工艺处理市政污水温室气体CH_4排放规律的研究

On the regularity of greenhouse gas CH_4 emission from A/O sewage-treating process

以我国广泛应用的A/O污水处理工艺为研究对象,分析了CH4排放情况。结果表明,CH4在各污水处理单元均有排放,其中曝气池和初沉池是CH4排放的主要单元,分别占污水处理过程CH4总排放量的77.73%和14.86%。在曝气池中CH4排放通量沿程迅速减小,主要集中在沿程前96 m。内回流比和曝气池曝气量可能影响曝气池CH4排放。调整回流比分别为200%、300%、400%,曝气池CH4排放通量随内回流比增大而减小;调整曝气量分别为3.5 m3/h、4.5 m3/h、5.5 m3/h、6.5 m3/h,曝气池CH4排放通量随曝气量提高而减小。

The paper intends to come up with our analysis of the CH4 emission based on the A/O sewage-treating process, which has widely been adopted in China. As a kind of important greenhouse gases, methane is known emitted from the sewage-treating plant and becomes one of the chief CH4 emission sources. Practically speaking, water surface can generally be divided into two categories： the aerated liquid surface （in aerated grit chambers and oxic tanks） and non-aerated liquid surface （in other sewage-treating units）. It is just based on the different characteristic features of the water surfaces that different methods can be adopted for sampling the CH4 emission. For example, two methods has now been used to collect the emitted CH4 from the sewage surface in the aerated and non-aerated areas, respectively, that is, the gas bag method and the static chamber method. And,then, it would be possible for the dissolved CH4 collected by means of a headspace gas method. And, next, all the CH4 gas samples can be analyzed by using a GC （Agilent 7890） equipped with a flame ioniza- tion detector （FID）, with its emission flux having been worked out. The results of our experiments indicate that it is possible to find there exits CH4 emission in all the sewage-treating units. More accurately speaking, the oxic tank and primarily setting tank, can be made to serve as the main CH4 emission units, which accounts for 77.73 % and 14.86% of the total emission. In addition, it can also be found that CH4 emission flux in the oxic tank tends to readily decrease along the way, while CH4 emission is mainly focused on the initial 96 me- ters. Moreover, we have also discovered that the internal recycling ratio and aeration rate are likely to influence the CH4 emission in the oxic tank. Furthermore, CH4 emission flux in the oxic tank is also found decreasing with the increase of the internal recycling ratio when the internal recycling rates tends to increase to 200%, 300% and 400%, respectively. However, CH4 emission flux has been found decreasing with the increase of the aeration rate in case it would be set to 3.5 m3/h, 4.5 m3/h, 5.5 m3/h and 6.5 m3/h, respectively.