比較不同前氧化方式處理優養化水體對消毒副產物生成之影響

Effects of preoxidation methods on DBPs formation in treatment of eutrophicated water

陳威誌(Wei-Chih Chen)

指導教授 ： 王根樹

國立臺灣大學/公共衛生學院/環境衛生研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01485

摘要

一般自來水廠會採用前加氯的方式，以氧化原水中一些污染物質，藉以減輕後續淨水程序之操作成本並提升處理效率。但氯在氧化污染物的同時，亦會與水中有機物質反應生成消毒副產物(Disinfection By-Products, DBPs)；而藻類也將提供部分消毒副產物前驅物質來源，不論是細胞本身或其胞外代謝產物。當前加氯與藻類反應後，將造成藻類細胞受損而釋放出胞內有機物質，因而增加了淨水中消毒副產物的前質。因此一但原水因為藻類大量繁殖而成為優氧化水體時，除了影響淨水效率外，也將增加大眾用水之健康風險。
本研究採用次氯酸鈉、高錳酸鉀、臭氧及二氧化氯等四種氧化劑，將含藻類原水分為藻類細胞部分(Intracellular organic matter, IOM)及胞外物質部分(Extracellular organic matter, EOM)後分別進行前氧化試驗，觀察IOM及EOM對消毒副產物生成之貢獻以及經傳統淨水程序後對消毒副產物前質之去除效果，嘗試找出處理優氧化水體時較合適之前氧化劑。
研究結果顯示，藉由氧化劑量與反應時間的控制，可避免淨水程序後淨水中三鹵甲烷(Trihalomethanes, THMs)前質的增加；但不論使用何種前氧化劑處理實驗室配製之含藻類原水，皆會使得淨水中含鹵乙酸(Haloacetic acids, HAAs)前質的增加；而這部分前質的增加皆主要來自於藻類細胞部分。此外，包括在採集金門太湖原水進行相同試驗後之結果顯示，清水中三鹵甲烷前質在前氧化處理後皆有降低，但使用臭氧和次氯酸鈉為前氧化劑處理藻類細胞部分時，淨水中消毒副產物的前質高於使用其他兩種前氧化劑之結果。綜合本研究之結果，在處理藻類大量繁殖或含有高濃度溴離子之原水時，高錳酸鉀對消毒副產物前質有較佳的去除效果。

關鍵字

消毒副產物 ； 銅綠微囊藻 ； 氯 ； 高錳酸鉀 ； 臭氧 ； 二氧化氯

並列摘要

Pre-chlorination is widely used in drinking water treatments to remove contaminants in raw water, reduce the coagulants cost and enhance the efficiency of operation process. However, chlorine reacts with natural organic matter (NOM) may also produce disinfection by-products (DBPs); and the presence of algae also increases DBPs precursors, from both intracellular organic matter (IOM) and extracellular organic matter (EOM).
Moreover, the reaction between chlorine and algal cells in eutrophic raw water during prechlorination may also increase the DBPs precursors in treated water because of the destruction of algal cells. Besides its impact on conventional water treatment processes, higher DBPs formation from prechlorination would raise the risk on human health.
This study intends to find an alternative preoxidant for treatment of eutrophic water. Potassium permanganate, ozone and chlorine dioxide were selected as the alternative preoxidants. The laboratory-cultured Microcystis aeruginosa (a species of blue-green algae) were chosen as the representative algae to evaluate the formation potential of DBPs from IOM and EOM after preoxidation and conventional water treatments.
The results showed that suitable control of preoxidants dosage and contact time could decrease trihalomethanes (THMs) precursors in treated water, but may increase the haloacetic acids (HAAs) precursors when laboratory cultured algal cells were used. However, preoxidation with ozone and chlorine for IOM produced higher level of DBPs precursors in treated water than potassium permanganate and chlorine dioxide. After conventional treatment processes, it was observed that potassium permanganate had better removal efficiency for DBPs precursors in IOM.

並列關鍵字

Disinfection by-products ； Microcystis aeruginosa ； Chlorine ； Potassium permanganate ； Ozone ； Chlorine dioxide

參考文獻

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