A large eddy simulation study to assess low-speed wind and baffle orientation effects in a water treatment sedimentation basin

Hydraulic performance of clarifiers in water and wastewater treatment plants significantly affects the settling efficiency of suspended particles. Structural and ambient parameters can deteriorate this performance. Through a verified three dimensional numerical study, we evaluated hydraulic performa...

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Bibliographic Details
Published in:Water science and technology 2018-05, Vol.2017 (2), p.412-421
Main Authors: Goodarzi, Danial, Lari, Kaveh Sookhak, Alighardashi, Abolghasem
Format: Article
Language:English
Subjects:
Baffles
Clarifiers
Computer simulation
Efficiency
Engineering
Environmental engineering
Flow velocity
Hydraulic retention time
Hydraulics
Large eddy simulation
Orientation
Particle Size
Residual stress
Retention time
Sedimentary basins
Sedimentation
Sedimentation & deposition
Settling
Simulation
Tracers
Turbulence models
Vortices
Waste Disposal, Fluid - methods
Waste Water - analysis
Wastewater
Wastewater treatment
Wastewater treatment plants
Water Movements
Water Purification - methods
Water quality
Water treatment
Wind
Wind effects
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Summary:Hydraulic performance of clarifiers in water and wastewater treatment plants significantly affects the settling efficiency of suspended particles. Structural and ambient parameters can deteriorate this performance. Through a verified three dimensional numerical study, we evaluated hydraulic performance and settling efficiency in a rectangular clarifier with a nominal hydraulic retention time (HRT) of 1 h and options for structural baffles with angles of 20°, 30°, 45° and 70°. Large eddy simulation and Lagrangian particle tracing were used to trace particles 80 to 850 μm in diameter. A passive scalar tracer study was conducted to reveal discrepancies in nominal and real HRT. By posing a 5 m/s wind, ten different scenarios were simulated. The wind caused 17% and 6% reduction in HRT and settling efficiency, respectively. Baffles improved these indicators with the 45° baffle showing the best performance with an approximate settling efficiency of 93%. The study highlighted the importance of using baffles, in particular for small size particles for which influencing factors such as wind deteriorate their settling efficiency.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2018.171