Study On The Sedimentation Characteristics And Transfer And Transformation Of Contaminants In Confluence Area Of Sewage Pipeline Network

For urban sewage pipe flow area pollutant deposition and erosion affect the stable operation of the problem,in this paper,through the establishment of urban sewage pipe system,explores the urban area of pipe flow under different flow scouring and deposition characteristics of pollutants in wastewater,analyzed the pipeline carbon,nitrogen and phosphorus in sediments and pollutants in the different vertical depth and confluence area along the migration law of parsing the confluence area changes of water quality in sewage plant pollutants,operation optimization and pipeline pipe flow sediment dredging for the city provides a theoretical basis.By studying the characteristics of sewage and sediment pollutants in different confluence areas under different flow states,the sewage pipeline can be divided into four functional areas along the pipeline,namely,stagnant area,separation area,maximum velocity area and flow recovery area.Among them,when V_branch/V_stem=0.15/0.25 and V_branch/V_stem=0.15/0.35,the overall sedimentary layer thickness of the pipeline decreased significantly by 5-10mm,and the sedimentation in the retention area and the separation area dominated,and the pollutant concentration increased.In the maximum velocity zone where the flow rate of sewage reaches the limit after confluence,the scour effect is dominant and the concentration of pollutants decreases most significantly.In the flow recovery area,the characteristics of pollutant deposition and scour are not significant.At the same time,pollutants deposited on the surface layer in each region are distributed within the range of 10-50 livm particle size mainly attached organic pollutants,accounting for an obvious increase of about 25%,while the proportion distributed within the range of≤10 livm particle size mainly attached nitrogen and phosphorus pollutants varies little.When V_branch/V_stem=0.15/0.35 and V_branch/V_stem=0.25/0.35,the decrease of sediment thickness in each region was only 3-6mm,but the pollutant concentration in the retention area and the separation area still increased slightly,and the pollutant change in the maximum flow rate area and the flow recovery area was small.Based on the rule of pollutant migration and transformation in the confluence region under the above different flow states,this study further analyzed the influence of pollutant deposition and scour in the confluence region on the inflow water quality of the sewage plant.The results show that when the flow rate is low,the large particulate pollutants naturally deposit in the wastewater,which makes the water quality of the wastewater plant contain a small amount of organic matter.At high flow rate,some granular pollutants are washed into pipeline sewage,increasing the content of organic matter in sewage,thus contributing to the change of the current situation of insufficient carbon sources in sewage treatment plants.