城市污水管网污染物沉积与冲刷释放规律研究

On the pollutant deposition and erosion release in the urban sewer networks

为明确城市污水管网中污染物沉积、冲刷释放及微生物降解作用对有机物去除的贡献,以管网中城市污水为研究对象,通过建立有沉积与无沉积的模拟管道,在首次冲刷的理论基础上得到管道污染物沉积释放计算模型,进而研究了不同流量下有机污染物的沉积与冲刷释放规律,并对不同流量下进出水的粒径分布及颗粒组成进行分析。结果表明,在管道6 h水力循环条件下,当流速为0.32 m/s时,污水中有机物变化以沉积贡献为主;当流速增加为管网最小设计流速0.6 m/s时,污染物沉积现象得到显著改善,冲刷释放效应增强;当流速进一步增加为0.9 m/s时,冲刷释放成为主要作用,生物降解作用微弱。

This paper is aimed to introduce its research findings on the influence of the sediment accumulation,the erosion release and the biodegradation on the organic pollutant removal in the sewer networks. In proceeding with our work,we have established a simulated sewer networks with and without sediments by sewage in the sewer network as experimental target. And then,we have put forward the hypothesis based on the theory of the first flush to help us to work out the calculation model of the sediment accumulation and erosion release. With the said calculation model as a supporting means,it would be possible for us to gain the corresponding organic matter variations of each device under the different flow velocities and in turn to work out the contribution of each effect. Furthermore,we have managed to identify and determine the sediment accumulation and the erosion release regularity. At the same time,we have also analyzed the particle size distribution in the sewage and the particle composition of the influent and effluent under the different flue velocities as well. The results of our measurement and investigation demonstrate that under the condition of 6-hour hydraulic flow,the flow velocity has been at about 0. 32 m/s,in which the sedimentation tends to account for the main cause of the organic matter removal,with the particles of size 125 μm being obviously deposited. However,when the flow rate has increased to 0. 60 m/s,that is to say,when it reaches the minimum flow velocity as is originally designed,the pollutant deposition can be expected to get significantly improved,with the particles of size 125 μm being deposited slightly. However,when the flow velocity is supposed to increase to 0. 90 m/s,the erosion release rate would turn to account for the chief cause for the organic matter removal with the weak biodegradation effect,in which the particles of size 125 μm may get to reveal little deposition. Thus,it can be concluded that the contribution of the sediment accumulation,the erosion release and the biodegradation tend to make the main contribution to the organic matter removal in the sewer networks,and,therefore,our research findings can be said to help to provide a theoretical basis for the distribution and prediction of the sewer sediment.