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Study on the Change of Residual Chlorine in the Drinking Water Distribution System
|關鍵字:||配水系統;drinking water distribution system;餘氯;水力特性;管型;管壁;因素分析;群落分析;迴歸分析;餘氯消耗模式;網際地理資料;residual chlorine;hydraulic characteristic;pipe type;pipe wall;factor analysis;cluster analysis;regression analysis;Chlorine-depletion model;Web-GIS||出版社:||環境工程學系||摘要:||
Residual chlorine change is commonly recognized as an excellent parameter in the world for studying drinking water quality in the distribution system. This research employed a model distribution system to investigate effects of pipe geometry and materials on the change of chlorine residuals. A field study on the residual chlorine change was also conducted to investigate spatial diversity of chlorine residuals in a real drinking water distribution system. Finally, a mathematical model that considers the hydraulic characteristics of pipe networks and the evolution of disinfectants was developed to predict residual free chlorine and combined chlorine in a real drinking water distribution system.
According to the study of a model distribution system, hydraulic parameters such as dispersion number, dead zone and flow exchange rate are all connected to flow rate and distance. The study points out that the dispersion number goes down and the dead zone rate goes up when water flowing through sections where pipe diameter has sudden changes or when it flowing through the front and rear of obstacles on pipe walls in a slower speed, flowing through the rear of obstacles on pipe walls in a faster speed, and flowing through some deeper caves.
The degree of residual chlorine distribution is related to these hydraulic characteristics parameters. For the reason to keep water quality in pipelines, it is better to reduce the existence of uneven sections as much as possible during underground pipeline settings. The study also points out the idea of reducing the effect of these uneven sections by slow flow spread effect or high speed turbulent flow eddy effect. Moreover, controlling the residual chlorine concentration effectively when it enters drinking water distribution system is another issue which engineers should be concerned about; the research has noticed that the lower residual chlorine concentration added at the beginning, the higher the decay rate occurred in the pipelines, and the more residual chlorine concentration dropped beyond anticipation. In the effect of pipe materials, the experiment has found the highest decay rate of residual chlorine in galvanized pipes and the lowest decay rate in PVC pipes; so it is necessary to frequently check the residual chlorine concentration in galvanized pipes which are often used to substitute for PVC pipes.
This study applied factor analysis, cluster analysis and regression analysis to determine the spatial diversity of chlorine residual in the distribution system of Feng-Yuan city. The study pointed out the concentration variations in the distributing system could be classified by factor analysis, which is helpful to find out the cause. As for the monitor or typical sampling sites, the study suggested using the results of factor analysis can decide the station quantity and employing rotated factor matrix (which appeared in the analyzing process) to choose out those typical ones. In the research of concentration level, the cluster analysis is regarded as a simple but scientic method. By combining the results of factor analysis and cluster analysis, the worst case scenarios for drinking water quality in the distribution network could be determined. Besides, to cut down the time and efforts of the maintenance staffs, the study addressed regression analysis to set up the relation between typical sampling sites and others, and the concentration warning values of typical ones.
In the simulation, not only combines Hardy Cross Method and Mass Balance Equations to build pipe network mode, also further employs the residual chlorine water quality parameters from the experimental data,linked up factor analysis to decide the node daily water uses, and considered the residual chlorine variations in finished water to advance the accuracy of the mode. It was validated by comparing its numerical solutions with the solutions of EPANET and the field sampling data of distribution. Practical application of the present model was also addressed.
Ultimately, for the purpose of making the presentation of simulated residual chlorine change in the pipe network simpler and more understandable, this study takes the advantage of Web-GIS in the space analysis. Through the technology of layer slicing and color gradient and with showing simple and clear color variation of water quality, it is able to display the results of concentration variation which contains value, time and space spread characteristics all together and lift the stimulation result to be more readable and evaluative.
|Appears in Collections:||環境工程學系所|
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