Numerical Simulation And Application Research On Water Flow And Quality In Urban Drainage Networks

This paper analyzes the current problems of aging and damage in sewage pipe networks,and constructs a hydraulic-water quality drainage network model for the research area’s sewage pipe network to numerically simulate the changes in water quantity and water quality inside the sewage pipe network.By collecting existing data and combining with on-site measured data,the hydraulic and water quality model parameters of the research area sewage pipe network model are calibrated to match the actual results,enabling accurate simulation of actual conditions.Through modeling methods,it is found that the current drainage network model can accurately simulate the complex hydraulic conditions and water quality changes in the sewage pipe network.During the experiment,the relative error range between simulated water quantity data inside the sewage pipe network and measured data is within 1.5%-17.9%,and the relative error range of pollutant concentrations in the water quality model calibration is reasonable.In summary,the constructed hydraulic-water quality drainage network model can be used for future simulation studies.The sewage pipe network in Yueyang Lake Area was analyzed,and based on the data collected by the research team on March 18-19,2023,the variations of pollutant concentration along the sewage pipe network at different times,in different types of residential areas,and inside the sewage pipe network were analyzed.It was found that the pollutant concentration was higher during the peak drainage period,and in general,the concentration was positively proportional to the user’s drainage volume,but the variation patterns of pollutant concentration were different at different locations.The pollutant concentration in various types of residential areas varied,and the COD and TP content in urban villages were significantly higher than those in residential areas due to people’s different living habits in different living areas.There is no significant change in the pollutant concentration inside the pipe during peak periods,indicating that pollutants decay less in the sewage pipe network when the flow rate is high.The decrease in TN and TP concentration during low periods is due to a small flow rate causing sedimentation in pipes,leading to a decrease in pollutant concentration.The data of influent water quantity and water quality of the sewage treatment plant were analyzed,and it was found that there was a positive correlation between the influent water quantity and water quality,as well as between the pollutant concentration and water quantity.The model was calibrated by simulating the influent water quantity of the sewage treatment plant,and the relative error range between the simulated results and the measured results was within-2.3%-16.1%.With an understanding of the factors influencing the pollutant concentration of the sewage treatment plant influent,the water quality concentration of the sewage treatment plant influent under different flow and water quality conditions was studied based on existing water quantity and quality data.The results showed that changes in water quality concentration significantly affect the influent water quality of the sewage treatment plant,and the sewage pipe network’s water quantity and quality have a significant impact on the influent water quality of the sewage treatment plant.To ensure efficient operation of the sewage treatment plant,the water quantity inside the sewage pipe network should be close to 7187.3 m3 per day,and the pipes should be inspected to prevent reduced water quality due to external water infiltration,which can lead to inefficient operation of the sewage treatment plant.