ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER

WU Jun

doi:10.13205/j.hjgc.202304001

Volume 41 Issue 4

Apr. 2023

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WU Jun. ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER[J]. ENVIRONMENTAL ENGINEERING , 2023, 41(4): 1-9. doi: 10.13205/j.hjgc.202304001

Citation:

WU Jun. ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER[J]. ENVIRONMENTAL ENGINEERING , 2023, 41(4): 1-9. doi: 10.13205/j.hjgc.202304001

WU Jun. ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER[J]. ENVIRONMENTAL ENGINEERING , 2023, 41(4): 1-9. doi: 10.13205/j.hjgc.202304001

Citation:

WU Jun. ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER[J]. ENVIRONMENTAL ENGINEERING , 2023, 41(4): 1-9. doi: 10.13205/j.hjgc.202304001

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ANALYSIS OF SETTLING VELOCITY OF PARTICULATES IN FLOWS IN DRY AND WET WEATHER FROM THE COMBINED SEWER

doi: 10.13205/j.hjgc.202304001

WU Jun^1,2

1. Shanghai Urban Water Resources Development & Utilization National Engineering Center Co., Ltd, Shanghai 200082, China;
2. Shanghai Chengtou Water Group Co., Ltd, Shanghai 200002, China

Received Date: 2022-02-25
Available Online: 2023-05-26
Publish Date: 2023-04-01

Abstract

Abstract

The drainage pipes accept rainwater runoff and dry flow sewage, and form the combined sewer consisting of rainwater and sewage in wet weather. Some particles settle to form sediment. Comparing the settling velocity (SV) of particles in the above-mentioned routes will help to improve the control efficiency of wet weather flow. A section of the combined sewer was selected to collect water and sediment samples. The elutriation separation method was used to analyze the SV of particles. Based on this, the fitting relationship between SV and mass ratio was established. The results showed that the proportion of particulate matter with SV≥0.265 mm/s in the rain-sewage combined sewer was similar to that of the sediment, but was different from the stormwater runoff and dry-weather flow. This indicated that during the rainy days, some sediments were eroded, significantly promoting the SV of particles in wet-weather flows. Furthermore, under each SV, the higher the rainfall, the smaller the proportion of particles below that SV, and the higher the proportion of the unsettled particulate pollutants. The results showed that: a) more particles with higher SV were eroded into the wet-weather flow under higher rainfall; b) when the flow increased, more unsettled particulate pollutants entered the downstream of the pipe, resulting in the reduction of the gravity interception efficiency. In addition, PAHs, Cd, Cr and Pb accounted for high proportions of particles with SV≥0.265 mm/s. Therefore, when SV=0.265 mm/s was set for gravity sedimentation treatment measures, PAHs, Cd, Cr and Pb will be effectively reduced. Based on the above data, the relationship between SV of particulates and the mass ratio can be established, namely x=lnB/(A-y)(R²>0.95), which was helpful to realize the rapid transformation of the mass ratio of particles and particulate pollutants under the specific SV.
- wet weather flow,
- settling velocity,
- particulate,
- drainage system

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References(37)

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