Estimation of Retained Pollutants in Separate Rainwater Pipeline Network

In order to quantitatively calculate the proportion of retained pollutants in a separate rainwater pipeline network to the total pollutants during rainfall conditions, the retained pollutants in the rainwater pipeline network of a research area were sampled and detected periodically, and the SWMM model was established based on the basic data of the research area. In addition, a method for calculating the amount of retained pollutants in the rainwater pipeline network was proposed, which was to calculate the amount of retained pollutants based on the detected pollutant concentration and depth ratio of the rainwater pipeline network. The data of retained pollutants were inputted into the established SWMM model, and the change of pollutant concentration at the outlet of the pipeline network with and without retained pollutants were analyzed and compared. The simulation results showed that the contribution rates of retained pollutants in the rainwater system to COD, NH ₃-N and TP pollutant loads were 43.30%, 92.75% and 58.83%, respectively. It could be concluded that the proportion of retained pollutants in the total pollutants of rainwater pipeline network was large.