Tracer test and hydraulic efficiency improvement of farm-pond wetlands
Date Issued
2014
Date
2014
Author(s)
Zeng, Yun-Qi
Abstract
Wetlands provide considerable benefits and promote biodiversity by offering habitat for water loving plants, birds and insects. Among various types of wetlands, free water surface constructed wetlands (CWs) are artificial wetlands designed to provide multiple functions, such as waste water treatment, ecosystem services, carbon reservoirs, and flood detention. CWs have been proposed as a cost-effective treatment for point and non-point source pollution in recent years. The treatment efficiency strongly depends on flow pattern and residence times of the flow condition. The treatment efficiency of CWs cannot be determined without understanding the flow dynamics of individual parcels of water through the wetland. This study thus presents a tracer experiment to estimate wetland residence time distributions and hydraulic efficiency. Both field investigation and numerical model experiment were conducted and examined. A horizontal two dimensional model, TABS-2, is employed to simulate the tracer tests. Then, varied of numerical experiments designed to achieve improve situ hydraulic efficiency.
The Chuangui pond in Taoyuan County was selected as field site, and use rhodamine-WT as the tracer to perform tracer tests to discuss residence time distribution of the constructed wetland. Three tracer tests are investigated on a 0.35 ha treatment wetland. The overall hydraulic efficient is calculated as 0.02-0.18 and reveals a poor hydraulic status. The results also indicate the worst hydraulic efficiency occurs at the deep water pond area. In order to improve hydraulic efficiency, 53 scenarios are designed to test the improvement efficiency with different water depths, flow discharge, configuration of inlet and outlet, and number and allocation of obstructions by using TABS-2 simulation. The results show that there is a high correlation between the water depth, flow and hydraulic efficiency. In this case, setting of obstruction is the key to effectively enhance hydraulic efficiency. In the case of set one obstruction, hydraulic efficiency can be raised to 0.68. In the other case of installing two obstructions, hydraulic efficiency can be raised to 1.05 which achieves a good hydraulic condition.
Subjects
人工溼地
水力效率
數值試驗
追蹤劑試驗
停留時間分佈
SDGs
Type
thesis
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