微米氣泡－生物濾床對於消毒副產物生成潛勢之影響

Effect of Disinfection Byproduct Formation Potential by Microbubble-Biofiltration

賴人暐(Jen-Wei Lai)

指導教授 ： 童心欣

國立臺灣大學/工學院/環境工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602320

摘要

金門榮湖水體富含營養鹽，長期下來造成水體優養化以及嚴重的季節性藻華現象，使水中含有大量溶解性有機物。然而，若自來水廠未能將其有效去除，會造成後端消毒程序產生消毒副產物，如：三鹵甲烷、鹵乙酸等。此外，亦有許多濃度不高但卻有較高毒性之氮系消毒副產物，如：鹵乙腈、鹵化硝基甲烷等生成，造成後端用水戶的暴露風險。現今，已可使用高級處理程序有效控制部分消毒副產物生成，然而，高級處理程序會提高能源消耗，且耗材可能造成環境二次汙染，故要如何兼顧用水安全以及環保的處理方式一直是所要面臨的課題。微米氣泡為粒徑小於50 µm之微小氣泡，當其存在於水中會縮小，最終爆破於水中，釋放具有氧化能力的自由基，由於其低耗能且對環境友善，在水及廢水處理上的應用也逐漸受到關注。本研究欲使用微米氣泡的特性，將水中疏水性有機碳物轉化成親水性有機物，並提高生物可分解性有機碳組成比例，並結合生物濾床以連續流方式循環過濾降低水中溶解性有機碳濃度，進而降低後端加氯消毒後消毒副產物生成風險。此外，藉由曝氣亦可提高水體溶氧量，在過濾時提高生物活性，進一步提升處理效率。本研究利用不同消毒劑進行消毒副產物生成潛勢試驗評估生物濾床對於消毒副產物前質去除效果。實驗結果顯示經過空氣及氧氣－微米氣泡以兩小時曝氣處理後之水體對於溶解性有機碳去除效果有限，僅對於三鹵甲烷與鹵乙腈等前質有去除效果。若結合生物濾床處理亦無法有效對溶解性有機碳以及三鹵甲烷、鹵乙酸及鹵乙腈等前質去除率有所提升。若以臭氧－微米氣泡對水樣進行處理可有效降低溶解性有機碳濃度及三鹵甲烷、鹵乙酸及鹵乙腈生成潛勢總量，然而，以臭氧－微米氣泡結合生物濾床循環過濾對於生物濾床過濾溶解性有機碳去除率雖有提升，但對於各消毒副產物前質去除率提升有限。比較以散氣頭及微米氣泡機曝氣臭氧之差異，結果顯示以散氣頭曝氣臭氧與微米氣泡臭氧對於溶解性有機碳以及消毒副產物生成潛勢去除效果相似。以微米氣泡長時間曝氣僅能些微改變水中溶解性有機碳組成比例，但對於提升生物可分解性有機碳比例效果並不明顯。總之，要利用微米氣泡之氧化能力於淨水處理程序中仍有待後續研究。

關鍵字

微米氣泡 ； 生物濾床 ； 三鹵甲烷 ； 鹵乙酸 ； 鹵乙腈 ； 消毒副產物生成潛勢

並列摘要

Lake Ron, a reservoir located on Kinman Island, is prone to eutrophication and seasonal algae blooming due to excessive livestock farming and inadequate water management. The results in elevated dissolved organic carbon (DOC) concentrations in the reservoir, which can be removed partially in conventional water treatment processes. The DOC in raw water will react with chlorine to form disinfection byproducts (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs) which are also known as carbonaceous DBPs (C-DBPs). Furthermore, nitrogenous DBPs (N-DBPs) such as haloacetonitriles (HANs), halonitromethanes (HNMs), which may have higher toxicity than C-DBPs, are also produced. Advanced water treatment processes can control the formation of DBPs. However, high energy consumption may be an important issue. Microbubble with the diameter is less than 50 µm, will gradually decrease in size and collapse in water. Oxidative free radicals will be generated after the microbubble eruption. The objectives of this study are to increase the ratio of biodegradable organic carbon (BDOC) in DOC and oxidize the hydrophobic natural organic matter(NOM) by microbubble aeration. At the same time, microbubble aeration is used in combination with biological filtration (biofiltration) to enhance the DOC removal efficiency. Moreover, microbubble aeration can also increase the dissolved oxygen (DO) concentration and enhance the biological activity in the biofilters. The DBP formation potential (DBP FP) test was used to evaluate DBP precursors removal efficiency with different disinfectants. The results showed that it was less effective in the removal of DOC but effective in removing to the precursors of THMs and HANs by both air- and oxygen-microbubble. In the microbubble aeration combined with biofiltration recycling process, it also showed no apparent DOC concentration reduction, the precursors of THMs, HAAs and HANs removal efficiency enhancement. Compared with direct biofiltration recycling process, the ozone-microbubble combined with biofiltration recycling process could indeed increase the removal efficiency of the DOC, but it still showed no noticeably increasing in the removal efficiency of DBP FP. Among original and microbubble ozonation, both of them had the similar ability to remove DOC and DBP FP. Hence, the microbubble treatment can only change the DOC structures slightly. In conclusion, application of the oxidizing potential of microbubbles in drinking water treatment processes requests attention for further research.

並列關鍵字

Microbubble ； biofiltration ； trihalomethanes (THMs) ； haloacetic acids (HAAs) ； haloacetonitrles (HANs) ； disinfection byproducts formation potential (DBP FP)

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