多点汇流下污水管网污染物迁变规律及其机制

To study the changing laws of pollutants under the condition of multi-point confluence of urban sewage pipe network and the mechanism of their influence on microbial reproduction, a set of sewage pipeline pilot system with multiple confluent points was established to explore the migration and transformation characteristics of the three main pollutants of carbon, nitrogen and sulfur in the sewage transportation process. The results showed that the concentration of dissolved chemical oxygen demand (SCOD) and sulfate (SO₄^2-) before the confluence point decreased, the concentration of NH₄⁺-N increased, and the confluence of branch pipes significantly increased the concentration of three types of pollutants at the confluence point. In the later stage, the water quality reached stability. Under the condition that the increase of various pollutants was basically unchanged due to the inlet of branch sewage, the concentration of SCOD decreased from about 320mg/L at the inlet to about 280mg/L at the outlet. The total increase of NH₄⁺-N under the action of ammonification was about 15mg/L, which was higher than the total increase of 12.5mg/L due to the confluences. The results showed that the consumption and metabolism of microorganisms in the confluent pipe network was the dominant factor for the change of carbon and nitrogen pollutants. The concentration of SO₄^2- at the inlet and outlet of the confluent pipe was about 20mg/L, indicating that the confluent pipe and biochemical metabolism maintained the content of SO₄^2- in a state of dynamic equilibrium. In addition, the analysis of the microbial reproduction process in the biological phase of the pipe network pilot system showed that the content of fermenting bacteria (FB), hydrogen-producing acetogen (HPA) and sulfate reducing bacteria (SRB) increased significantly with the propagation time, and the abundance increased at different confluence points along the process. To sum up, the multi-point confluence caused the fluctuation of sewage water quality, which promoted the multiplication and proliferation of microorganisms in the biological phase of the pipe network, and enhanced the dominant position of its metabolism in the transformation of pollutants in the sewage pipe network, making the transformation of pollutants in the pipe network more significant.