Combined Sewage Overflow Control Based On SWMM

Combined sewage overflow is an important factor for the black odor of water in the old city.Choosing a reasonable overflow control scheme is extremely important for the sewage interception works and the treatment of black and odorous water.In this paper,the research is carried out in conjunction with the black odorous water improvement project,taking the overflow pollution control of the black odorous water body sewage interception pipe project in the downtown area of Guixi as an example.The main research contents of this article are as follows.(1)The central area of Guixi was selected as the research area.In conjunction with the black and odorous water improvement project of Caojia Lake,the surrounding area of Caojia Lake in Guixi City was investigated and analyzed,and its point source pollution and non-point source pollution were analyzed.survey.WaterDesk software was used to extract the pipe network length,pipe diameter,buried depth,and slope information from the original terrain file,and a SWMM model for the study area was established through data collection.(2)The rainfall data was selected using the Chicago rain pattern combined with the local heavy rain intensity formula in Guixi,and the measured rainfall data was combined with the Nash coefficient method to determine the final modeling parameters.The SWMM model was used to simulate the rainfall with a small and medium recurrence period as the background.The rainfall scenarios at different recurrence periods were designed to investigate its overflow rule.The outflow and overflow of the pipe network with different interception scales were counted,and the total overflow and its pollutant load was obtained.(3)The zero dimensional water quality model is used to model the water environmental capacity.The calculation results of the target environmental capacity of COD,TN and TP are 776.2kg/d,41.6kg/d and 8.3kg/d.Using the liner fit function of origin9 software to fit the annual COD cutoff scatter diagram under different closure multiples,the minimum interception ratio meeting the target environmental capacity of class ? water quality standard is 19.21.(4)The effective volume of the regulating and storage tank determined by the interception ratio method is 3600m3,and the regulating and storage efficiency is verified.The results show that the CSOs regulating and storage tank can fully store the overflow sewage when recurrence period is 0.5.And the overflow control rate can reach 57.4%when recurrence period is 1.In order to achieve the best regulation and storage effect,the CSOs regulation and storage tank of Caojia Lake adopts the method of hydraulic flushing and turning bucket to wash and discharge sand,and the unit flushing volume of hydraulic turning bucket is 651.9L/m determined by the empirical formula method.