Study On The Impact Factors Of The Urban River Water Quality

With the rapid development of economy and urbanization, the industrial and agricultural production is further scaling up. Besides, the dense population has made negative influence on environment, which has led to serious pollution of watercourses and damage of their ecosystem.The water has little self-purification capacity to sustain its quality. More seriously appears the black phenomenon. This thesis mainly focuses on a typical urban polluted watercourse—using Suzhou Guandu River as the example and PCA method to evaluate its water quality. The result shows the main pollutants are CODcr, NH3-N and TP.The serious pollution load and weak self-purification capacity have deteriorated urban watercourse water quality.In order to improve and sustain water quality for a long time,the key question is restoring self-purification capacity and constructing a positive cycle for ecosystem in the basis of reducing pollution load and removing pollutants rapidly.The self-purification of natural water is an extremely complex process and is influenced by many factors. This thesis explores the method of improving the self-purification capacity of urban watercourse based on some factors. By building the outdoor simulated watercourse according to the prototype of Guandu River and choosing flow rate, reaeration capacity, microbial property, original density of pollutants and temperature as the five impact factors, a comparative study of their respective impact on water quality is made. The relation between degradation coefficient of pollutants and these five factors is studied.This thesis uses the clustering method to analyze comprehensively the degree of contributions the five factors make to water self-purification capacity. By making use of this method, the different degrees of influence these five factors make on self-purification capacity are classified by similarity measurement.The result shows that flow rate and microbial property are more effective in improving water self-purification capacity, and reaeration capacity is next. This thesis makes single-factor and three-factor simulation test of the above three factors, which demonstrates that kCODcr, kNH3-N, and kTP under three-factor combination respectively increase by 279%,330% and 86.4% and the improvement of self-purification capacity is far better than the single-factor situation. Thus, the findings of this experiment can be applied to projects of river improvement of Guandu River. It is suggested that the above three factors should be combined and use the integrated technology of percolation purification, artificial hydraulic system and aeration to improve the water assimilative capacity and regain its self-purification capacity.The proposed system paves the way for the development of comprehensive water environmental management of urban watercourse.