Study On Methods Of Source Water Quality Security

Water, the basis of life, is an important resource for human life maintenance and society development. Although there are objectively abundant water reserves on the earth and more and more effort is being made to protect it all over the world, the water environment tends to deteriorate globally and a lot of water sources have lost their original values. Moreover, since accidental contaminations and terrorist attacks have lead to a great danger to drinking water supplies, water safety becomes an important factor of maintaining the stability of society.The methods of insuring source water quality are the main concerns in this thesis. Based on the description of the necessity and stringency of safety insurance studies on water supply systems, some topics are presented as well, including the methods of assessing water supply systems' vulnerability, early warning systems of source water quality and the methods of predicting source water quality. Additionally, some discussions on the applications of these methods in practical projects are depicted at the same time. The main content consists of these following parts:1) Introduction of vulnerability assessment into safety insurance studies on water supply systemsAccording to the documents of USEPA and other departments, the conventional methods of vulnerability assessment on water supply systems are introduced in this paper. Through the investigations and studies on present situations of water supply system in Xi'an, it has been found that the system can meet the requirements under normal conditions, while when high load contaminations and accidental contaminations occurs, the conventional treatment process, including coagulation, sedimentation and filtration, can not ensure the treated water quality. Furthermore, there are little studies on the overall situations and safety pitfalls of Xi'an water supply system, and yet the emergency measures are still not complete. 2) Studies on early warning systems of source water qualitySeveral aspects of early warning systems of source water quality are analyzed in this study, including the definition, characteristics, constitutions, operation theories and applications. Meanwhile, some results have been used in practical work and the effects are good.3) Chaos theory and its applications in the prediction of source water qualityThe applications of chaos method in source water quality prediction are discussed after the introduction of several conventional methods. The chaos model of Lyapunov exponent is established for predicting the source water quality. By using this method the analysis was carried out on the time series of weekly averaged values of 12 water quality indexes, which are obtained from JieYuan water plant in Tianjin. The delay time (Ï„), Lyapunov exponent and embedding dimension (m) of each index are calculated for prediction. The errors are less than 10%, which indicates that chaos theory is feasible in the prediction of source water quality.