| Lake Eutrophication is a serious problem in our country, and outer pollution control is an effective way to solve this problem.The author introduced the concept, classification and the decontaminate mechanism of constructed wetland in this paper, and emphasized on the feasibility and application advantage of constructed wetland in outer pollution control of Lake Eutrophication. This study was under the project—Taihu water pollution controlling and water rehabilitation technology & engineering demonstration, which belongs to special project of key science and technology in the national Tenth-Five-Year-Plan. In this constructed wetland pilot-scale experiment, we study the decontaminate effect through selecting different substrates, plants and water flow patterns in different hydraulic loading. By this mean, we can find out a best combination of substrate, plant and water flow pattern in constructed wetland to reduce the N ,P pollution of lake and create an environment of ecological regeneration of lake. We reach these conclusions:The plant is very important in constructed wetland, and it also have the ability of N ,P removal .The N, P content of the plants is different in constructed wetland. Canna chineresisw has the top N, P content and the top contribute to N, P removal.The substrate zeolite can improve the removal efficiency of constructed. The unit with zeolite has higher removal efficiency of NH3-N and TN ,but has normal NO3-N removal efficiency. In addition, the change of thickness of gravel substrate has no distinct effect on removal efficiency.Different water flow patterns have different influence in removal efficiency. The removal efficiency of composite flow pattern (vertical flow plus subsurface flow) is higher than others, and there is no distinct correlation between vertical flow + subsurface flow and subsurface flow plus vertical flow in N removal. The subsurface flow and vertical flow have middle removal efficiency and the free surface system has the lowest removal efficiency.Different hydraulic loading in constructed wetland have different removal efficiency. The TN, NH3-N and NO3-N removal efficiency increased when hydraulic loading is low and decreased with the high hydraulic loading .The change of hydraulic loading decide the pollutant loading, and has the effect on oxygen reversion and growth of plant which effect on removal efficiency.The vertical flow plus subsurface flow constructed wetland with Canna chineresisw and zeolite substrate which has the advantage of few using area, high removal efficiency has a good prospect of application in Taihu area. |
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