多点汇流下污水管网污染物迁变规律及其机制

为研究城市污水管网多点汇流条件下污染物的迁变规律及其对微生物繁衍的影响机制，建立一套多汇流点位的污水管道中试系统，探究污水输送过程中碳，氮，硫3类主要污染物质的迁移转化特性.结果表明，汇流点前溶解态化学需氧量（SCOD）和硫酸盐（SO₄^2-）浓度下降，氨氮（NH₄⁺-N）浓度上升，支管汇流使得汇流点3类污染物浓度显著增加.后期水质达到稳定，在保证支管污水的汇入导致各类污染物增加量基本不变的情况下，SCOD浓度由进口的320mg/L左右下降至出口的280mg/L左右，在氨化作用下导致的NH₄⁺-N总增加量在15mg/L左右，高于因汇流产生的增加总量12.5mg/L左右，结果表明汇流管网系统中微生物的消耗代谢作用是碳氮类污染物变化的主导因素，而SO₄^2-后期进出口浓度均在20mg/L左右，说明支管汇流和生化代谢使SO₄^2-的含量维持在动态平衡的状态.此外，对管网中试系统生物相中微生物繁衍过程进行分析可知，发酵菌（FB），产氢产乙酸菌（HPA），硫酸盐还原菌（SRB）的含量随繁衍时间显著增加，并在沿程的不同汇流点处出现丰度升高现象.综上所述，在多点汇流导致污水水质波动的作用下，促进了管网生物相中微生物的繁衍增殖，并增强了其代谢作用在污水管网污染物转化的主导地位，使得污染物在管网输送过程中呈现更为显著的转化现象.

Mechanism of pollutant transformation in sewage pipe network under multi-point confluence

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.