Modeling Total Suspended Solids in Combined Sewer Systems

• Main Author: Zhang, Weilan
• Format: Others
• Published: OpenSIUC 2012
• Subjects: Combined sewer system; Total suspended solids; Transport model; Transport rate
• Online Access: https://opensiuc.lib.siu.edu/theses/803; https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1811&context=theses

The untreated overflow of combined sewer system contains a variety of pollutants that can contaminate the receiving water body. Total suspended solids (TSS) transported in the sewer networks can adsorb these pollutants and become the main contaminant source. Existing models contain a numerous formulas that make the calculation process complex and time consuming. A simplified model was presented in this thesis to simulate the process of TSS transport in combined sewer pipes. The combined sewer system evaluated was a combination of an existing sewer system in Le Marais and an example system provided with the Storm Water Management Model (SWMM). SWMM was used in this research to simulate the rainfall event, pollutant build-up and wash-off process, and to provide hydraulic calculations for the combined sewer system. A spreadsheet model was created to calculate the TSS concentration profile and flow velocity profile. The total TSS transport rate was computed using a numerical estimation of the integral of the concentration in the cross-section area multiplied by the velocity. The flow depth, velocity, and Froude number of each pipe was calculated to show that the combined sewer system was under proper working conditions. The first flush phenomenon was observed by plotting the TSS concentration pollutograph of the combined sewer system. From the TSS transport pollutograph, the maximum transport rate was found (0.2609 kg/s at 6:45). The study of TSS profile showed that the concentration distribution was based on the solid density. The TSS particle also affected the transport rate. A sensitivity analysis of particle size was conducted in this thesis. A second order polynomial was used to describe the relationship between median particle size d50¬ ¬and TSS transport rate.