FANG Yan,FU Da-kang,LI Ji-hong,et al.Relationship between River Water Quality and Rainfall Events in Separate System with Mixing of Rainwater and Sewage[J].China Water & Wastewater,2021,37(7 7):107-113.
Relationship between River Water Quality and Rainfall Events in Separate System with Mixing of Rainwater and Sewage
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第37卷
Number:
7 7
Page:
107-113
Column:
Date of publication:
2021-04-01
- Abstract:
- There are runoff pollution and mixing of rainwater and sewage in areas with separate system. Rainfall is still an important factor affecting the fluctuation of river water quality. Rainfall data and water quality of Datong Central River located in a typical area with separate system of Kunshan High-tech Zone were continuously monitored for one year, and variation in river water quality with rainfall intensity and rainfall interval was analyzed. Results indicated that the fluctuation of river water quality was related to rainfall in 24 hours, rainfall intensity and rainfall interval. When the rainfall in 24 hours was less than 5 mm, profile of COD in the river water after rainfall was decreasing. When the rainfall in 24 hours was more than 5 mm, COD of the river water after rainfall was generally higher than that before rainfall. Fluctuation of NH4+-N in the river water after the rainfall was related to the combined effect of erosion and dilution. The erosion and dilution effects were balanced when the rainfall in 24 hours was less than 18 mm, while the dilution effect was greater than the erosion effect when the rainfall in 24 hours was 18-22 mm. The erosion effect was more obvious when the rainfall in 24 hours was more than 22 mm. With the increase of rainfall grade, NH4+-N in the river water after rainfall increased firstly and then decreased, and the increasing ranges of NH4+-N after light rain, moderate rain, heavy rain and storm were <0.2 mg/L, 0.3-0.5 mg/L, 0.4-0.7 mg/L and 0.7-1.0 mg/L, respectively. Profile of COD generally decreased firstly and then increased gradually, and the combined effect of runoff dilution and pipeline sediment erosion was most obvious during moderate rain and heavy rain. Generally, COD rose slowly about 4 days after the rainfall, and the decreasing ranges of COD after light rain, moderate rain, heavy rain and storm were 2-4 mg/L, 5-9 mg/L, 7-10 mg/L and >10 mg/L, respectively. In addition, continuous rainfall events and excessive rainfall interval would result in a large fluctuation of pollutants concentration in the river water after rainfall events. The maximum fluctuation of COD and NH+4-N in river water occurred when the interval period was only one day, while the minimum fluctuation occurred when the interval period was five days.
Last Update:
2021-04-01