西部人居环境学刊2025，Vol.40Issue(5)：9-15,7.DOI:10.13791/j.cnki.hsfwest.20250922003
合流制溢流污水扩散模拟及其对水环境的影响
Study on diffusion simulation of combined sewer overflow and its impact on water environment
摘要
Abstract
The issue of water pollution caused by Combined Sewer Overflow(CSO)is one of the most pressing concerns in urban water management,especially in cities with combined sewer systems where rainwater and wastewater share the same pipeline network.During periods of intense rainfall,the capacity of the system may be exceeded,causing untreated wastewater to overflow into nearby water bodies,leading to severe pollution.This phenomenon not only affects water quality but also poses a significant risk to aquatic ecosystems,public health,and the overall environmental integrity of urban areas.In this study,a southwestern city was chosen for the research,with the primary objective to explore the diffusion and impact of CSO-related pollutants on receiving water bodies under various rainfall conditions.The study used the MIKE21 two-dimensional hydrodynamic-water quality coupled model to simulate the diffusion process of overflow wastewater in the river.This model was selected for its ability to represent both the hydrodynamic and water quality aspects of the river system.To ensure the accuracy of the model,the research team collected real-time hydrological and water quality data for model calibration.The Nash efficiency coefficient(NSE)for water level simulation was calculated to be 0.93,confirming that the model provided a good fit to the observed data and could be relied upon for subsequent predictions.The primary focus of the research was to evaluate the impact of different rainfall intensities on the movement and diffusion of pollutants in the river system.For this purpose,three distinct rainfall scenarios were simulated:light rain(daily rainfall ranging from 0.1 to 4.9 mm),moderate rain(daily rainfall ranging from 10 to 24.9 mm),and heavy rain(daily rainfall ranging from 25 to 49.9 mm).The goal was to examine how different rainfall levels influence the pollutant load in the overflow and their subsequent diffusion in the water body.The findings from the simulations revealed that heavy rain conditions caused the highest initial peak pollutant concentrations in the receiving water body.Specifically,the concentrations of key pollutants,such as Chemical Oxygen Demand(COD),Total Nitrogen(TN),Ammonium Nitrogen(NH4+-N),and Total Phosphorus(TP),increased significantly and remained elevated in the downstream areas for an extended period after the overflow.This suggests that under heavy rainfall,the overflow wastewater not only causes a sharp rise in pollutant concentrations but also leads to a prolonged contamination period,further degrading water quality.These results are particularly concerning because the pollutants persisted in the receiving water body,and thus exacerbating the impact on aquatic ecosystems and potentially violating environmental regulations.In moderate rain scenarios,the pollutant plume expanded,but the range and concentration of pollutants were not as extreme as under heavy rain.The concentration peaks were moderate,and the pollutants spread over a smaller distance,implying that the extent of the pollution was more localized compared to the heavy rain scenario.On the other hand,during light rain conditions,the pollutant spread was largely confined to the area near the overflow point,with concentrations rapidly decreasing as the distance from the overflow increased.This indicates that in smaller,more manageable rainfall events,the overflow impact is less severe and more easily diluted within the receiving water body.Regardless of the rainfall scenario,the simulations revealed that the receiving river section's water quality exceeded the Class II standard for surface water quality,as specified by the Environmental Quality Standards for Surface Water.This indicates that CSO events can result in significant pollution that can degrade the water quality to an extent that may pose environmental and public health risks.The model further demonstrated that different pollutants exhibited varying attenuation rates.COD and NH4+-N concentrations decreased rapidly as the pollutants traveled downstream,suggesting that these substances are more easily diluted or degraded over distance.However,TN and TP concentrations declined more gradually,indicating that these pollutants,often found in particulate or adsorbed forms,persist longer in the water and require more time for natural attenuation processes such as sedimentation and biological uptake.The findings of this study underscore the need for comprehensive strategies to manage CSO pollution,especially during extreme rainfall events.Several recommendations were made based on the results.Firstly,the study advocates for enhanced source control measures,such as reducing the amount of untreated runoff entering the sewer system.Implementing initial retention mechanisms to store the overflow during early stages of rainfall would also significantly reduce the pollution load released into water bodies.Secondly,ecological water supplementation is recommended as a supplementary measure to improve water quality by enhancing natural self-purification processes.This could include strategies such as introducing additional flows of clean water into the affected water bodies to dilute pollutants and promote the degradation of contaminants.In conclusion,this study demonstrates the critical need for adaptive and proactive management of CSO events and provides a scientific foundation for the development of strategies to minimize the negative impacts of stormwater overflows on urban water systems.The adoption of comprehensive and integrated approaches will be key to achieving long-term water quality sustainability in urban areas prone to CSOs.关键词
合流制溢流/对流扩散模拟/水质影响/降雨强度/污染控制策略Key words
combined sewer overflow/advection-diffusion simulation/water quality impact/rainfall intensity/pollution control strategy分类
环境科学引用本文复制引用
何强,程呈,夏鸿志远,高旭,扈庆,毛圆翔,敖良根..合流制溢流污水扩散模拟及其对水环境的影响[J].西部人居环境学刊,2025,40(5):9-15,7.基金项目
国家重点研发计划项目(2022YFC38005) （2022YFC38005）
重庆水务集团股份有限公司创新项目 （）
