| 摘要: | 台灣自來水公司第六區處於103年度開始，部分淨水場已開始採用鐵系藥劑—氯化鐵作為主要混凝劑，由於氯化鐵的使用量增加，另一水質管制項目”鐵”的檢測亦成為淨水場內的日常檢測項目，目前「鐵」的水質管制濃度為0.3 ppm，然而在pH > 4的環境下，Fe3+就容易形成沉澱氫氧化鐵，因此使用氯化鐵更應注意配水管網區域的酸鹼度變化、配水管網內的鐵離子濃度以及供水系統內是否有鐵沉積物的存在。
有鑑於此，本研究以原台南市市區(縣市合併前的台南市)範圍，作為的研究實地試驗的區域，定期定點進行水質檢測分析，項目主要為總鐵濃度、pH值、氧化還原電位、餘氯值以及濁度，測點點位選擇與六區供水單位確認執行，包含清水池到配水管網的前中後總共15端點。研究目的為了解從清水池到配水管網前中後端，水中鐵濃度的變化，並研析水中鐵濃度與其他水質的關聯性，研究中並採樣配水管網的中後端的管內沉積物，研討分析目前供水管網內沉積物主要之型態。
結果顯示，在烏山頭淨水廠輸配管線中，以W-1而言，總鐵濃度為0.01~0.03 ppm之間，總鐵濃度與其他水質項目皆無顯著相關。以W-2而言，總鐵濃度與ORP顯著相關，而ORP值與濁度值呈現高度相關，研判此處總鐵因氧化形成濁度顆粒，抑或是採樣時管線內沉積的氫氧化鐵顆粒受擾動而帶出，會增加濁度的貢獻。以W-4而言，總鐵濃度與其他水質項目皆無顯著相關，總鐵濃度為0.02~0.12 ppm之間。
在潭頂淨水廠輸配管線中，以T-3而言，總鐵濃度與其他水質項目皆無顯著相關，總鐵濃度為0.01~0.37 ppm 之間，最高濃度0.37 ppm出現在第一次採樣，於此處研判總鐵因氧化形成濁度顆粒，因採樣時擾動將管線內沉積的顆粒帶出。以T-4與T-5而言，總鐵濃度與其他水質項目皆無顯著相關，總鐵濃度為0.01~0.04 ppm之間，遠低於內控值0.24 ppm。在南化淨水廠輸配管線中，以N-4而言，總鐵濃度與各項水質項目並無顯著相關，不過總鐵濃度為0.01~0.04 ppm 之間，遠低於內控值0.24 ppm。
綜觀第六區處烏山頭、潭頂與南化供水區域內管線內沉積物採樣分析，經EDS元素分析可發現主要為鋁氧化物及矽氧化物，Al2O3和SiO2皆屬於環境中天然的濁度顆粒。也有鐵元素的存在，最高值僅為1.66%。值得注意的是烏山頭供水系統末端管線沉積物採樣分析(編號W-P2)，有碳元素含量高達有20.22%，推判應是有碳酸鹽類的物質在此區域沉積。
Some water purification plants in Taiwan Water Supply Company’s sixth district have begun to use ferric chloride from the year of 2014. Due to the increased use of ferric chloride, the detection of another water quality control target “iron”, it has also become a daily testing item in the water purification plants. At present, the water control concentration of "total iron" is 0.3 ppm. However, in the environment of pH > 4, Fe3+ is easy to form precipitated iron hydroxide. Therefore, it is more important that the change in pH of the water pipe network, the concentration of iron ions in the water distribution network, and the presence of iron deposits in the water supply system
In this study, we conducted water quality testing and analysis within the scope of the original Tainan City area for regularly field test. The main items are total iron concentration, pH value, redox potential (ORP), residual chlorine and turbidity. The selection points of the measuring point and the confirmation of the Taiwan Water Supply Company’s sixth district, including the clear water reservoir to the front and rear of the water distribution network, a total of 15 points. The purpose of the study is to survey the change of iron concentration in the water from the clear water reservoir to the water distribution network. And the correlation between iron concentration and other water quality items were also studied. We also investigated the sediment in the middle and rear end of the water distribution network, the main elements of sediments in the current water supply network were analyzed.
The results showed that in the distribution pipeline of Wushantou Water Purification Plant, the total iron concentration is between 0.01 and 0.03 ppm at the point of W-1, and the total iron concentration is not significantly correlated with other water quality projects. In the case of W-2, the total iron concentration is significantly correlated with ORP, and the ORP value is highly correlated with the turbidity value. It is determined whether the total iron is oxidized to form turbidity particles, or the iron hydroxide particles deposited in the pipeline during sampling, the disturbed and brought out of turbidity particles will increase the turbidity. In the case of W-4, the total iron concentration was not significantly correlated with other water quality projects, and the total iron concentration was between 0.02 and 0.12 ppm. In the Tanting Water Purification Plant distribution pipeline, at the point of T-3, the total iron concentration was not significantly correlated with other water quality items. The total iron concentration was between 0.01 and 0.37 ppm, and the highest concentration of 0.37 ppm appeared in the first sampling. Here, it is judged that the total iron is oxidized to form turbidity particles, and the particles deposited in the pipeline are taken out by the disturbance during first sampling. For T-4 and T-5, the total iron concentration was not significantly correlated with other water quality items. The total iron concentration was between 0.01 and 0.04 ppm, which was much lower than the control value of 0.24 ppm. In the transmission line of the Nanhua Water Purification Plant, the total iron concentration is not significantly related to the various water quality items in terms of N-4, but the total iron concentration is between 0.01 and 0.04 ppm, which is much lower than the internal control value of 0.24 ppm.
The analysis of the sediments in the pipelines in the Wushantou, Tanting and Nanhua water supply areas in the sixth district, the EDS elemental analysis can be found mainly elements were aluminum oxides and antimony oxides such as Al2O3 and SiO2 which are natural turbidity particles. There is also the presence of iron element, however, the highest value is only 1.66%. It is worth noting that the sediment sampling analysis of the No. W-P2, end pipeline of the Wushantou water supply system. The results showed carbon content of up to 20.22%. It is estimated that carbonates material should be deposited in this area. |
