Ecological Restoration Of Urban River And Its Effects On Transformation Of Nitrogen

Urban rivers, as a part of nature river basin, participate the whole hydrologic cycle and have been profoundly influenced by the urban environment. So, under the presently circumstances of urban pollution,in order to supervise the construction of urban ecological river network, rehabilitating ecological structure and function of river, it is really important to discovery the relationship between river structure & procedure of Ecological restoration and water body self-purification, environmental capacity & nutrition cycle of nitrogen.This article analyzes physical conditions like speed of flow, the bending coefficient, active photosynthesis radiation and restoration methods like aeration, bioremediation to the changes of nitrogen self-purification, and we obtained following important conclusion:The speed of flow has an important effect on the concentration of nitrogen in water. When the speed of flow blows 0.5 m/h, concentration of TN in water is most highly, contaminations in the river were mainly in the form of deposit, rate of biodegradation is very slowly. The rate of water reaeration by atmosphere increased greatly in the state of flowing water, Mineralization and Nitrification becomes more easily. When the speed of flow exceeds 1.5 m/h, the concentration of nitrogen significantly decreased, which showed that strengthening hydrodynamic condition could promote degradation of nitrogen.Increase of the bending coefficient of rivers could also advantageous to the decontamination of nitrogen in the water body. But too large bending coefficient could increase the contacted area between water and bottom sludge, which would affect the water quality by the pollutants in the bottom sludge diffuse to the water body. The experiment result indicated that in comparison with TN, increasement of bending coefficient was more good for degradation of NH3-N and NO3--N. Another effect of urbanized development to the river was the big building intensely reduced the active photosynthesis radiation of the river ecosystem. The change of illumination intensity would affect the structure and productivity of critter community in water body, as well as pollutant conversion process. it was found that, the concentration of nitrogen in water body which under straight sunshine was obviously lower than in the water body away from direct sunlight, so was the phosphorus. Therefore, this should cause highly recognition in the urban planning and construction of urban ecological river network.Sediment with high organic substances content Releases more nitrogen to water. The concentration of TN reached 14.17mg/L in water when the concentration of organic matter in Sediment is 41.23g/kg. Sediment with less organic substances releases NH3-N quickly, but less latent capaurban. Sediment with high organic substances content has great potential of releasing NH3-N.Hydrodictyon reticulatum have a better capaurban of pollution tolerant than Ceratophyllum. Hydrodictyon reticulatum must take precedence over Ceratophyllum in Ecological restoration of severely eutrophic river. When the nutrient fall off to less degree, Ceratophyllum can do as a following-up bioremediation plant.Aeration of river water can promote degradation of TN and NH3–N.Comparing with river water which is not aerated. The removal rate of TN and NH3–N can reach 81% and 92% in aerated water. At this point bioremediation with indigenous aquatic plants can get good results and high success rate. The concentration of TN and NH3–N can keep lying below 1.0mg/L and 0.5mg/L. The reduce of effective optical radiation must be avoided in bioremediation.