On Optimal Design of Treatment Detention Wetland
Date Issued
2008
Date
2008
Author(s)
Kuo, Pin-Han
Abstract
Treatment Detention Wetland means adding the FWS (free water surface) wetland into the detention pond. The function of Treatment Detention Wetland is to provide detention volume in the flood period and waste water treatment in ordinary days. Nevertheless, the designs of the detention pond and the FWS wetland are different. Take Taiwan for an example, the design of water depth is always over 1.5 - meters in Taiwan. According to EPA manual (2000), however, the range of water depth in the FWS wetland is 0.15-0.6 meters. As a result, the water depth lays a crucial role in Treatment Detention Wetland for seeking of satisfying both detention function and waste water treatment function. When the depth of the FWS wetland is as higher as the designing of the detention pond, there must exist some contradictions in Hydraulic efficiency, λ , and the pollution removal rates. A horizontal two dimensional model, TABS-2, was employed in this study to simulate the tracer tests for evaluating hydraulic efficiency, λ and the pollution–BOD, ammonia, and nitrate–removal rates based on Reed et al. (1995) with the simulated RTD (residence time distribution). Besides, this study defines a index, Effective Treatment Time Ratio–et ,to quantify the effective treatment time for pollution removing. The results demonstrate that when the water depth rises from 0.1 to 2.5 meters, the RTD are divergent, the effective volume rate, ev, is only half remain in 2.5-meter-depth and the hydraulic efficiency, λ, decrease from 0.86 to 0.15. Beside, the Effective Treatment Time Ratio–et decreases as the water depth elevated. Therefore, the difference of the pollution removal rates between the actual-situations and the theory-situations is higher due to the declined hydraulic efficiency, λ. This study integrates the result of modeling to bring up an optimal designing procedure for Treatment – Detention – Wetland – designing. Therefore, the follow-up designers could refer to this procedure to strike the optimal designing. By the way, this study also analyzes a case drew up by the project, Master Planning for Environmental Restoration and Sustainable Revitalization in Chiayi Coast Region, to demonstrate how to apply the procedure.
Subjects
Detention Wetland
Water Depth
Hydraulic Efficiency
Effective Treatment Time Ratio
Optimal Designing Procedure
SDGs
Type
thesis
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