Research On Generating Constructed Wetlands For River

Eutrophication is the hypertrophic state of aquatic owing to unbalance of in-out nutriment, which becomes the main aquatic environmental problem all over the world and key factors restrict human society and economy developing. So the theoretic and applied studies on the eco-restoration for water bodies of eutrophication are very significative.Constructed wetland technology is a kind of low-cost and high-efficiency ecosystem engineering for eutrophied water treatment, but the application of this technology rests on primary phase in our country, especially for eutrophied water treatment in river. Therefor, the author puts forward a way on generating constructed wetlands for river from the low concentrations of river water pollutants, large flow volume, water going up and down frequently, obvious seasonal variation of pollutant concentration, etc. Comparing with traditional constructed wetland, the constructed wetland has advantages of good performance, simple structure, convenient management and low cost.In this paper, the linchpin of generating constructed wetlands for river includes wetland bed and choosing wetland plants. But now, the wetland bed is mainly designed by experience formula and engineering experience, which effects the purification effect. Numerical simulation of 3D flow is applied on the flow inside wetland to optimize parameters of generating wetland bed and current conditions inside wetland by founding numerical projects, based on Navier-Stokes equations and the standard k-εturbulent mode, applied SIMPLE algorithm, given reasonable boundary. Through numerical simulation of example, the optimal parameters of generating wetland bed is educed, i.e. S=2.5D&B=0.7D. And the effects on river flow of constructed wetlands are analyzed by flow field, average longitudinal velocity, average lateral velocity of river sections and the distributing with runoff of river sections, the result shows that the effect for river flow is small. Moreover, the model is found with AHP to optimize the groups of wetland plants from ability of decontamination, resistance, value of zoology and esthetics as well as value of economy. There is a comparative analysis between four groups of wetland plants with the model in the example, the result shows that the multipurpose benefit on group of Canna indica and Scirpus validus is best.Through studies above, the author tries to provide scientific basis and technological parameters for design and management of constructed wetland and to put forward a new way on the treatment for river water of eutrophication.