| 摘要: |
| 针对城市合流制排水系统溢流造成的受
纳水体污染问题，选取西南某城市溢流口所处河
段为研究区域，基于MIKE21二维水动力—水质
耦合模型模拟溢流污水在河道中的扩散过程。通
过采集实测水文与水质数据进行模型率定，水位
模拟Nash 效率系数达0.93，表明模型具备良好
精度。设定小雨（日降雨量0.1～4.9 mm）、中雨
（日降雨量10～24.9 mm）、大雨（日降雨量25～
49.9 mm）三种降雨情景下，研究污染物在水环
境中迁移扩散的规律。结果表明：大雨工况下溢
流初期污染物浓度峰值高、传播距离远，受纳水
体COD、TN、NH4?-N、TP浓度均显著上升且在
下游长期滞留；中雨工况下污染带影响范围和浓
度峰值居中；小雨工况下污染物主要局限在近溢
流口区域，浓度沿程快速衰减。在3 种情景中，
溢流均导致受纳河段水质超出《地表水环境标
准》中的Ⅱ类水质标准。不同污染物的衰减速率
存在差异：COD 和NH4?-N 浓度随距离迅速降
低，TN和TP 则衰减相对缓慢，其中COD衰减
最快，速率为0.104 mg/（L·m）。研究建议加强
溢流污染源头截流与初期调蓄，建设生态补水等
措施，以降低暴雨溢流对水环境的冲击。 |
| 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 |
| DOI：10.13791/j.cnki.hsfwest.20250922003 |
| 分类号: |
| 基金项目:国家重点研发计划项目（2022YFC38005）；重庆水务集团股份有限公司创新项目 |
|
| Study on diffusion simulation of combined sewer overflow and its impact on waterenvironment |
|
HE Qiang,CHENG Cheng,XIA Hongzhiyuan,GAO Xu,HU Qing,MAO Yuanxiang,AO Lianggen
|
| 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 twodimensional
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 ofpollutants 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 selfpurification
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. |
| Key words: combined sewer overflow advection-diffusion simulation water quality impact rainfall intensity pollution control strategy |
