曝气沉砂池除砂机理分析

Analysis of grit removal mechanism of aerated grit chamber

针对曝气沉砂池小试装置模型,通过配砂实验对沉砂池除砂率进行统计分析,研究曝气强度与HRT对沉砂池除砂率的影响。实验结果表明,不同曝气强度下,随着HRT变化,除砂率逐渐上升,并最终趋于平衡状态;不同HRT下,曝气强度与除砂率近似呈现一定的线性关系,且随着曝气强度的增大,除砂率降低;在HRT小于1 min时,砂粒的运行路径和沉降时间缩短,不利于砂粒的去除;在HRT大于1 min时,其中1、3和4 min,随着气水比的增加除砂率降低幅度相对较小,曝气所引起的横向环流在一定程度上有利于砂粒的沉降,而HRT为2 min时,除砂率降幅却很大,这与砂粒在曝气沉砂池池体断面分布有关,即断面处旋转流速和水平流速的大小变化将影响砂粒的运动;相比曝气强度,HRT对除砂率的影响较大。

In this research, the influences of aeration intensity and HRT （hydraulic retention time） on the removal rate of grit chamberere were studied. We conducted experiments on a pilot scale aeration grit chamber model by sand mixing method, and analyzed data using statistic methods. The results show that under various aeration intensity conditions, the grit removal rate always increases with the increase of HRT, until it comes to an equilibrium; under different HRT, aeration intensity and grit removal rate have an approximate linearity, and the grit removal rate decreases with the increase of aeration intensity. When HRT is less than 1 rain, the path and settling time of sand is too short to remove the grit. When HRT is more than 1 min, the cases are different ： when HRTs are 1 min, 3 min or 4 min, the grit removal rate descends moderately with the increase of gas-water ratio, which is because the transverse circulation caused by aeration is somehow contributive to sand settlement to a cer- tain extent. But when HRT is 2 min, the grit removal rate descends rapidly with the increase of gas-water ratio, which can be explained by sand distribution on basin section, i.e. the change of rotating velocity and horizontal velocity on the section can affect the motion of the grit. HRT has a greater influence on grit removal rate than aeration intensity.