Study On The Operation Control And Rules Of Nitrogen Transfer In Constructed Wetlands

The constructed wetland is an ecological sewage treatment with good removal effects and low construction and operation cost. However, for the lack of systematical study on purificatory mechanism of wetlands, constructed wetlands technology is applied mainly depending on experience. As a result, its further development is disturbed to some extent.In this paper, horizontal flow wetlands with various kinds of plants grown and vertical flow wetlands with reeds planted are first studied on their operation characteristics in treating the sewage out from the primary sedimentary basin. After more than one year's experimental research, purificatory function and relevant factors of wetlands are comprehensively grasped. Based on it, the optimal operation condition is then determined. Finally, the nitrogen transferring rules and removing mechanism in sewage treatment system of wetlands is fundamentally discussed.Researches show that horizontal flow wetlands with plants grown have steadier removal effects. When average temperature is 20 degrees centigrade and the optimal hydraulic condition is reached (i.e. HRT 5.5 hours and out-waterline 60 centimeters), the removal percentage of CODCr, TN, TP in horizontal flow wetlands with reeds is respectively around 73.1%, 61.2%, 52.2%. By comparison of all kinds of wetlands under the same experimental condition, horizontal flow wetlands have better removal effects than blank ones, but inferior to vertical ones, among which wetlands with reeds and cannas have marked nitrogen removal effects and wetlands with camellias perform well through out the winter. Moreover, results are also obtained that plant selection and management of growing cycle affect the operational stability of wetlands and there exists a notable correlation between plants'photosynthesis and wetlands'nitrogen removal effects, which can be consider as a significant index for plant selection.By virtue of the study on nitrogen removal system in wetlands, it can be discovered that the amount of volatile nitrogen barely accounts for less than 0.5%, while substrata in wetlands only provides medi-action for microbial decomposing and vegetable assimilation, in which microbial assimilation and decomposing action dominate. Furthermore, plants in wetlands also play an important role in promoting the whole nitrogen removal system of wetlands.Finally, experiments demonstrate that the constructed wetland technology has a certain applicable value in sewage treatment and take an advantage in economic and technological aspects.