Study On Purification Efficiency Of Sewage In Constructed Wetlands

Water is the important natural resources for the human survival and development, as well as an important restriction factor of natural eco-environment. Water requirement and sewage is increasingly increased with the rapid expansion of urban area and development of industry. Water pollution restricts the development of economy and human health. The water pollution has become one of the serious environmental problems faced by the global nowadays. As soon as possible to increasing the level and the efficiency of sewage treatment in order to reduce the influence caused by pollution of water resources for sustainable development of the national economy negative impact. But, at present, there are many factors baffling the sewage treatment development, funds and techniques are the two main factors. Especially in some small towns and rural areas which are absent for funds, how to treat the domestic sewage is the most focused question. It is the common attention that researching new sewage treatment techniques in environmental engineering field.The constructed wetland of the new municipal sewage treatment techniques has merits such as stable outflow water quality, strongly impact resistance load, the lower of infrastructure cost and operating cost, easily maintaining, and aesthetics value. As well as the effective removal of pollutants, has the availability of denitrification and dephosphorization. And now more and more attention. Constructed wetland has been widely applied in sewage treatment, agriculture point source pollution, surface source pollution and the treatment domestic eutrophication of the water bodies.By theoretical analysis and practical investigation, designed to simulate small scale constructed wetland system. This paper mainly studied and discussed different types, plant selection, different concentration, purifying effect and influence factors in the wetland system. The result showed:(1) Different types constructed wetland have different remove efficiency. At hydraulic retention time is 1d, vertical flow constructed wetland for COD, NH4+-N, TN, TP removal efficiency of the best, the average removal rate of COD, NH4+-N, TN, TP was 59.8%, 66.2%, 75.2% and 53.5%. Between the subsurface flow and vertical flow constructed wetlands have little differences. The surface flow constructed wetland for all pollutants removal efficiency is lower than the first two.(2) Wetland plant played an important role in the constructed wetland, it have the ability of nitrogen, phosphorus removal. Through the test research of subsurface flow constructed wetland, which plants reeds,cattail and acorus calamus respectively, analyzed effect of three plants on the purifying the sewage, and different hydraulic retention time under the law changes. The results show that in the best operating conditions, COD, NH4+-N, TN, TP in the removal rate of 54.9%,75.4%,77.9% and 67.2%. Three plants contrast test presents that cattail purifying effect is significantly better than the reeds and acorus calamus. The COD, NH4+-N, TN, TP best removal rate reached to 67.2%, 90.0%, 89.7%, 88.9% by cattail. Have plants planted subsurface flow constructed wetland for sewage treatment effect of COD, NH4+-N, TN is better than no plants check systems, but of TP is no significant difference.(3) Sewage concentration subsurface flow constructed wetland system of COD, NH4+-N, TN removal efficiency is little effect, and the removal efficiency of TP has great influence.