Migration And Transformation Of Sediments Pollution In Rainwater Pipeline And Its Inducing Effect On River Black Odor

In view of the lack of research on the occurrence characteristics,migration and transformation law of rainwater pipeline pollutants and their interaction with the environment.Taking the typical rainwater pipe network in the central urban area of a city in North China as the research object,the temporal and spatial distribution characteristics of pollutants including sulfide in the pipeline are evaluated;To explore the migration and transformation law of pollutants at the sediment water interface under different flow rates and different pollution conditions.On this basis,the effects of different concentrations of sulfur pollution in the pipeline and flushing out SS on the river water environment are studied,and the response of river sediment to pollution under different pollution conditions is explored.It is found that the overlying water of rainwater pipeline is neutral,weak alkaline and mostly anaerobic.The average concentrations of COD,TN,TP and S^2-in the water are 84.54 mg/L,25.98 mg/L,2.51 mg/L and 3.24 mg/L respectively,which is much higher than the standard of surface class V water.The contents of TOM,TN and TP in the sediments of L-X pump station decreased along the way,while the sediment pollution of H-T pump station increased along the way;In terms of time,there are large quantities of pipeline pollutants in the early and middle rainy seasons.The pipeline sediment is mainly composed of large particles such as sand,but the occurrence of medium and small particles is high.Rainwater pipeline pollutants rich in nitrogen,phosphorus and sulfur have a great risk of eutrophication and black odor in the downstream river.The scouring experiment found that when the flow velocity was 0.14 m/s,the pollutants in SS were mainly released.When the flow velocity increased to 0.38 m/s,the resuspended large particle size SS increased,and the adsorption of pollutants in SS was enhanced.When the sediment with low water content is scoured by the flow velocity above 0.25 m/s,more SS is resuspended;The smaller the occurrence difference of TOM,TN and TP among sediment particles with different particle sizes,the smaller the influence of flow velocity on pollutant concentration in water.It is found in the simulation experiment that the input of S^2-load or SO₄^2-load above 100 mg/L will lead to the release of TN and TP in the sediment,increase the concentration of nitrogen and phosphorus in the water,and bring the risk of water eutrophication.The input of S^2-load will accumulate AVS in the sediment and cause black odor in the water.When S^2-and SO₄^2-loads cooperate with carbon source,the generation of black odor in water is more rapid and obvious,and the degradation of TOM and TN in sediment is inhibited.The SS flushed out of the pipeline will cause temporary and slight water deterioration in the water due to its black odor characteristics.Under the influence of S^2-and SO₄^2-loads,the black odor in the overlying water of the highly polluted sediment is more obvious,and AVS in the sediment is significantly accumulated.The pollution in the rainwater pipeline is serious,and the pollutants migrate downstream when the water is washed.The pollutants in the rainwater pipeline will induce significant black odor in the river after entering the river.