自來水消毒副產物生成動力探討-以金門太湖淨水廠為例

金門太湖原水長期受到季節性藻華以及優養化的影響，造成水中溶解性有機物濃度偏高，使得三鹵甲烷、鹵乙酸及鹵乙腈等消毒副產物在加氯程序當中大量生成，影響後續飲用水的安全性，其中三鹵甲烷易於超過台灣環保署管制標準(THM4 80 μgL-1)。本研究探討太湖原水中消毒副產物經由消毒程序後之生成特性，並管制之碳系消毒副產物如三鹵甲烷、鹵乙酸及鹵乙腈、三氯硝基甲烷等微量氮系消毒副產物作為生成動力指標。在生成特性曲線結果中發現太湖原水使用不同加藥量的次氯酸鈉在相近的曝露值(CT值)時鹵乙腈在越低濃度消毒劑加藥條件下有越較高的生成量(每單位溶解性有機碳具1.57 μgL-1 HAN4產生量)之趨勢，使用越高劑量則有降解現象越明顯，且在低劑量消毒劑條件次氯酸鈉促使鹵乙腈生成量高於氯胺。同時，透過同位素氯胺搭配氣相質譜層析儀進行試驗，可發現二氯乙腈(Dichloroacetonitrile)，鹵乙腈水體中生成主要物種，其生成量隨氯胺曝露值線性相關，且水體氮源構成之鹵乙腈14N-DCAN在低氯胺加藥量下生成比例提高(在本研究中3 mg-Cl2L-1 劑量氯胺條件下14N-DCAN與15N-DCAN生成量比值約為48.8:50.2)。太湖淨水前中慢濾池處理程序可去除大部份前加氯過程所產生之鹵乙酸和鹵乙腈，隨不同處理程序下在單位溶解性有機碳也同時表現出不同消毒副產物生成潛勢和生成動力，說明處理程序水質之改變。在配水管網模擬試驗中結果發現總三鹵甲烷易於在管網停留時間24小時內大量生成(實際消毒池出流水模擬24小時生成量111.2 μgL-1)。總和結果說明使用前加氯和後加氯胺較易於控制配水管網中管制消毒副產物和部份微量氮系消毒副產物之生成。

關鍵字

氯胺；消毒副產物；三鹵甲烷；鹵乙腈；三氯硝基甲烷

並列摘要

Human activity and regular drought weather increases the dissolved organic matter in fresh water reservoirs on Kinmen Island near the southeast shore of China. This results in substantial disinfection by-product formation in finished water which easily exceeded Taiwan EPA’s drinking water standard (80 μgL-1 for total trihalomethanes). The formation kinetic experiments were conducted using raw water from TaiLake, one of the major reservoirs on Kinmen Island. The formation kinetic curves indicated that high dosage of sodium hypochlorite lead to haloacetonitriles decay. For the same dosage, in low range, haloacetonitrile formation was higher with sodium hypochlorite than with chloramine. Trichloronitromethane formation was increased when chloramine was used as disinfectant. Dichloroacetonitrle, one of major species of haloacetonitriles observed, might come from both dissolved organic nitrogen and chloramine. By using nitrogen isotope with GC-MS, dichloroacetonitrile formation from chloramine is correlated linearly with disinfectant exposure (CT value) despite the dosage. Dichloroacetonitrile formation ratio from DON was increased at low disinfectant exposure (with chloramine initial dosage, 14N-DCAN to 15N-DCAN formation ratio was 48.8:50.2 in seven days raction in this study). Slow sand filtration in water treatment plant removes haloacetonitrles and haloacetic acids effectively. Different DBPs formation normalized by organic carbon unit kinetic and potential results from treatment process effluents was observed, which sμggest treatment process affect water quality (SUVA, DON, DIN, etc.). Simulated distribution system test indicated that peak trihalomethanes formation can be observed within 24 hours of retention time (trihlaomethane formation 111.2 μgL-1 in 24 hours SDS test for disinfection effluent sample on site). The results provide evidence that simultaneous prechlorination and postchloramination can be applied to better control regulated total trihalomethanes and potential nitrogenous disinfection by-product formation.

並列關鍵字

chloramine ； disinfection by-product ； trihalomethane ； haloacetonitrle ； trichloronitromethane

參考文獻

王翔生. (2007). 加強混凝去除金門太湖原水天然有機物之探討. (碩士), 臺灣大學, 台北市.

莊易學. (2013). 氮系消毒副產物於天然水體間之生成機制. (博士), 臺灣大學, 台北市.

Badawy, M. I., Gad-Allah, T. A., Ali, M. E. M., & Yoon, Y. (2012). Minimization of the formation of disinfection by-products. Chemosphere, 89(3), 235-240. doi: 10.1016/j.chemosphere.2012.04.025

Bond, T., Huang, J., Templeton, M. R., & Graham, N. (2011). Occurrence and control of nitrogenous disinfection by-products in drinking water--a review. Water Res, 45(15), 4341-4354. doi: 10.1016/j.watres.2011.05.034

Bond, T., Templeton, M. R., & Graham, N. (2012). Precursors of nitrogenous disinfection by-products in drinking water--a critical review and analysis. J Hazard Mater, 235-236, 1-16. doi: 10.1016/j.jhazmat.2012.07.017

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自來水消毒副產物生成動力探討-以金門太湖淨水廠為例

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