The Study On Evolution Mechanisms Of N And P And Inner Flow Characters In A Modified Subsurface Constructed Wetland

The wetland is a water treatment mode springing up since 70's. It makes use of the action of medium, aquatic plants and microorganism, purifies the wastewater though a series of physical, chemical and biological ways. Since West Germany built the constructed wetland in 1974, the technology has popularized and applicated in Europe, and developed rapidly in U.S.A. and Canada etc.Recently, a great deal of special studies discovered that nitrogen and phosphorus could stimulate algae and photosynthesis aquatic plants growing up, which aggravated the eutrophication of the water bodies. Reducing the discharge amount of nutritive salt in the wastewater (especially N and P) has aroused recognition world widely. Especially in developed country, there were strict control standards toward N and P in discharge water. Therefore, to study N and P removal principle in wetland is necessary. The recent study advanced that the N and P removal of the wetland was due to the together action of medium, aquatic plants and microorganism. The researches showed that flow conditions effluenced the physicochemical property in the environment of wetland, import and export of wastewater, therefore, it effluenced the removal effect on wastewater. However, for the effluence of wetland construction, plant roots, biomembrane etc. the flow conditions in wetlands are complex and the research on the fields now is less.The thesis emphasized on N and P distribution and removal efficiency in a modified constructed subsurface wetland which called Wavy-Subsurface Constructed Wetland (W-SFCW), and gave the primary analysis on the inner flow characters in wetland. The main content concludes that:(1) Through the comparative experiment study, it analyzed the removal efficiency of each part in W-SFCW and SFCW, so that we could further master the improvement of the removal on N and P of the inner parts in W-SFCW, thereby, the thesis offered the base for optimizing the design of wetlands.(2) While, the thesis investigated the distribute of the flow in the wetland, adopting the reactor theory in chemistry engineering, it studied the residence time distribute in the system, then it deepened the understanding of the character of wetland technology, promoted the realization of 'black box theory' on the purify mechanism, which could help us reduce the dead angles and short flow, also, it made us deeply aware the function of subsurface flow constructed wetland, stimulated wetland technology being applied more reasonably and effectively and improving steadily.The data and fruits of this thesis are benefit to optimize the wetlands design and functioning.