Hydrodynamic modelling of free water-surface constructed storm water wetlands using a finite volume technique

One of the key factors in designing free water-surface constructed wetlands (FWS CW) is the hydraulic efficiency (λ), which depends primarily on the retention time of the polluted storm water. Increasing the hydraulic retention time (HRT) at various flow levels will increase λ of the overall constru...

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Bibliographic Details
Published in:Environmental technology 2015-10, Vol.36 (20), p.2532-2547
Main Authors: Zounemat-Kermani, Mohammad, Scholz, Miklas, Tondar, Mohammad-Mahdi
Format: Article
Language:English
Subjects:
Aspect ratio
Climatic Processes
Computer Simulation
Construction
Fluid flow
hydraulic efficiency
Hydraulics
Hydrodynamics
Inlets
Mathematical analysis
Mathematical models
Models, Theoretical
obstruction
pond
Retention
retention time
Stormwater
Turbulence
Turbulence models
Turbulent flow
two-dimensional simulation
Water Movements
Wetlands
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Summary:One of the key factors in designing free water-surface constructed wetlands (FWS CW) is the hydraulic efficiency (λ), which depends primarily on the retention time of the polluted storm water. Increasing the hydraulic retention time (HRT) at various flow levels will increase λ of the overall constructed wetland (CW). The effects of characteristic geometric features that increase HRT were explored through the use of a two-dimensional depth-average hydrodynamic model. This numerical model was developed to solve the equations of continuity and motions on an unstructured triangular mesh using the Galerkin finite volume formulation and equations of the k-ε turbulence model. Eighty-nine diverse forms of artificial FWS CW with 11 different aspect ratios were numerically simulated and subsequently analysed for four scenarios: rectangular CW, modified rectangular CW with rounded edges, different inlet/outlet configurations of CW, and surface and submerged obstructions in front of the inlet part of the CW. Results from the simulations showed that increasing the aspect ratio has a direct influence on the enhancement of λ in all cases. However, the aspect ratio should be at least 9 in order to achieve an appropriate rate for λ in rectangular CW. Modified rounded rectangular CW improved λ by up to 23%, which allowed for the selection of a reduced aspect ratio. Simulation results showed that CW with low aspect ratios benefited from obstructions and optimized inlet/outlet configurations in terms of improved HRT.
ISSN:0959-3330
1479-487X
DOI:10.1080/09593330.2015.1036785