Ecological Restoration Measures Of Polluted Rivers

Nansi lake basin is an important water source turnover of the east route of the South-to-North Water Transfer Project,and Xiaosha river is a main channel of the lower lake of Nansi Lake, responsible for water transfer from Jiangsu Province to Nansi Lake.Xiaosha River is short,narrow and shallow. In recent years, with the rapid development of industrial and agricultural production, the river drainage pressure is growing larger, resulting in rerious water pollution and destroyed river ecological system. The paper explored the role of rivers reactor on water quality improvement by studying the purification ability of the plant body flowing in water, removal efficiency of overshadow on invasive species,and influence of hydraulic structures on Dissolved Oxygen.It evaluated water quality change trend of seven monitoring sections of Xiaosha River from2009to2011,analyzed the contamination source, put forward ecological restoration countermeasures,landscape design project and principles of resuming water quality, to give advice and suggestions for ecological reconstruction of Xiaosha River and water safety of the east route of the South-to-North Water Transfer Project.The water factor analysis of September2009showed that organic pollutants was serious in Jiangji bridge section and from the farmland to Zhuqiao rubber dam section, poisonous and harmful material pollution was serious in Jiangji bridge north and Jiukong bridge section water, No.2water sample from Jiangji bridge north section was the most serious, water quality of all monitoring sections from good to bad successively was damaged dam,down farmland, poplar woods,Zhuqiao rubber dam, Jiukong bridge, Jiangji bridge north and Jiangji bridge south.The paper analysed the trend of water quality change of all sections by single index method, classified and evaluated water quality change of all sections by synthetical index method. The results showed the water quality of middle of Xiaosha river was changing better, the quality of all sections belonged to5type in September2009and2010,5of7sections pertained to Class Ⅳ, only poplar woods and damaged dam sections reached Class Vin September2011. To study the influence of river ecological system on the river water quality, we trial-produced a river reactor model, studied the effect of aeration, hydrologic cycle of different vegetations without aeration and the influence of rubber dam model on dissolved oxygen. Experiments showed that the effect of aeration on the water pollutants purification was significant, and a water cycle of aeration can reduce ammonia nitrogen and COD contaminants to60-70%. As Dracaena sanderiana, the removal rate of water pollutants under dynamic was dozens of times that the static.The purifying effect of different types vegetation compositions was also different, the mode of Dracaena sanderiana+Eichhornia crassipes+Hydrocotyle vulgaris could quickly achieve good effect and maintain the efficiency of purifying water quality in a long time.The initial effect of the mode of Eichhornia crassipes+Hydrocotyle vulgaris was good,and then slower. Dracaena sanderiana could refine sewage,but rate was not quick. The influence of the rubber dam to dissolved oxygen was huge.The dissolved oxygen difference of both sides of the rubber dam model was between0.8to3.3mg/l in the river reactor model with Dracaena sanderiana,and it was between1to15mg/l in the river reactor model with the mode of four different plants.The paper explored the feasibility of removing alien species by controlling the shade.According to relevant scientific research, this paper put forward ecological restoration and water quality improvement strategy for Xiaosha river, and designed the bank landscape ecological system solutions, fully build a green, healthy, sustainable development ecological system. Water quality recovery strategy, in addition to the river ecological restoration measures, should pay attention to controling the sources of pollution, the benefits of hydraulic structures for water quality improvement also should be made use of.