Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/5143
標題: 自來水配水系統中餘氯變化之研究
Study on the Change of Residual Chlorine in the Drinking Water Distribution System
作者: 李連堯
Lee, Lienyao
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: 
餘氯濃度變化是世界各國公認研究自來水配水系統中水質好壞的最好依據。因此本研究分別利用實驗室的管線模廠設備及實場採樣的分析模擬,以期能在有限的研究資源下找出影響管網餘氯濃度變化因素、建立實場分析方法及呈現管網餘氯濃度變化模擬結果。
模廠的研究指出,雖然延散數、死角區比率及交換流量等水力特性參數皆與流速及管線距離有關,但這些既有的流況會受到管型及管壁的影響,例如管線直徑突縮(擴)的地方、低流速時管壁障礙物前後方、高流速時的管壁障礙物後方、較深的孔穴等均會使管線流體的延散數下降,死角區比率上升。
模廠管線中餘氯分布均勻程度與這些水力特性參數有著密切的關係。因此為保持管線中的水質,管線在埋設時應儘量減少不平整地方的存在。而對於這些不平整地方的影響,研究指出可藉由低流速的擴散效應或高流速的紊流渦流效應來減少。此外,有效控制進入配水系統的餘氯濃度是另一個水質參數要注意的地方,因為研究發現若一開始添加的餘氯濃度較低時,則會在管線中會出現較高的消耗速率,使餘氯濃度下降程度比預期大。至於在管材影響方面,實驗指出餘氯在鍍鋅材質的管線中消耗速率最快,在塑膠材質的管線中消耗速率最慢,故常用來替代塑膠管的鍍鋅管應多注意管線中餘氯濃度減少趨勢。
在實場配水系統方面,藉由台灣中部豐原市區配水管線的餘氯濃度變化,本研究利用因素分析、群落分析及迴歸分析等統計技術來建立管網水質分析方法。研究中指出有關配水系統中餘氯濃度的變化情況,可利用因素分析對供水區域加以分類。至於在水質監測站或代表性採樣點的規劃方面,研究中建議可利用因素分析的結果來決定代表性採樣點的數目,利用分析過程的轉軸負荷矩陣中選擇代表性採樣點。而在配水管網中餘氯濃度高低趨勢的研究,研究中認為群落分析不失為一種簡單又科學的方法。此外,為減少水質維護人員的時間及人力,研究中提出可利用迴歸分析來建立代表性採樣點與其他採樣點間的關係及這些代表性採樣點的餘氯濃度預警值。
在管網模式建立方面,本研究除結合Hardy-Cross法及質量平衡方程式等建立管網模式外,並更進一步採用實驗室模廠求得的餘氯水質參數、結合因素分析以建立結點用水量、考慮淨水廠清水中的餘氯變化等等以提高模式模擬的正確性。與EPANET模式及實場採樣的結果比較顯示,本研究所建立的模式可正確、有效地預估管線中餘氯隨時間與空間變化的情形。另外,研究中亦顯示結合因素分析等統計技術,除能更便於進行時間與空間變化的討論外,也較易尋找影響管線中餘氯濃度變化的因素。
最後,在管網水質模式模擬結果的呈現方面,為達到簡單易懂的目的,本研究中利用網際地理資訊系統(Web-GIS)在空間分析上優勢,透過圖層切割和顏色漸層的技術以簡單易懂的水質顏色變化,呈現出同時具有數值、時間、空間分佈特性的濃度變化結果,提高模擬結果的可讀性及判斷性。

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.
URI: http://hdl.handle.net/11455/5143
Appears in Collections:環境工程學系所

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