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Effects of Preoxidations on the Formation of DBPs for Selected Compounds
Disinfection by-products (DBPs),Imidazole,Metronidazole,Benzalkonium chloride (BKC),Metformin,Pre-chlorination,Ozonation,UV/H2O2 photolysis,
|Publication Year :||2012|
|Abstract:||新興汙染物近年來受到廣泛的關注，因為其對於環境及生物可能具有潛在的危害，而且在全球的河川、湖泊等水體皆可偵測到不同物質的汙染。在眾多新興污染物的類別中，藥物及個人照護用品(pharmaceutical and personal care products, PPCPs)特別受到注意。經過人體或動物吸收排放以及不當的丟棄後，PPCPs可能與汙水和淨水廠中的處理過程中與消毒劑產生作用，進而生成消毒副產物。由於許多消毒副產物對於人體具有毒性，因此了解其生成機制及特性十分重要。影響消毒副產物生成的可能原因與前質結構以及中間產物特性有關，而近年來為了提升水質而發展出高級氧化處理程序(Advanced oxidation processes，AOPs)來作為前氧化方式以期降解水中有機物，經過前氧化的前質在處理後可能發生結構上的改變而影響後端消毒副產物的生成。本篇研究考慮苯環、含氮雜環、不飽和脂肪鏈、四級銨鹽等結構上的特性，挑選四種廣泛被使用的PPCPs，包括咪唑(Imidazole)、甲硝唑(Metronidazole)、氯化苯二甲羥銨(Benzalkonium chloride，BKC)和二甲雙胍(Metformin)，評估其經過加氯、臭氧以及紫外光結合過氧化氫等前氧化步驟後，前趨物特性變化(溶解性有機碳和氮、二甲基胺和全波長掃描)以及碳系和氮系消毒副產物(三鹵甲烷、含鹵丙酮、含鹵乙腈、N-亞硝基二甲胺、三氯硝基甲烷)間生成潛能變化的趨勢。研究結果發現，BKC是碳系和氮系消毒副產物重要的潛在前趨物，無論是否經過前氧化處理皆能生成大量的消毒副產物。綜觀三種前氧化方式及不同消毒副產物生成情形，經過前氧化後三氯硝基甲烷是最主要生成的消毒副產物。另外，經由臭氧前處理並無法有效的降低四種化合物的消毒副產物生成潛能，經處理後消毒副產物生成反而有所提升。而咪唑(Imidazole)則不利於三氯化的消毒副產物種生成。|
Recently, the concerns of pharmaceutical and personal care products (PPCPs) present in the aquatic environment has grown because they have been detected in rivers, lakes, streams, and ground waters throughout the world. In addition, municipal wastewater effluents can have impacts on the compositions of organic matters in receiving waters. The presences of PPCPs not only threat the environmental ecosystems, but also can react with disinfectants to generate emerging disinfection by-products (DBPs). DBPs have been considered a public health problem due to their potential health risks to human beings. In addition to the types of disinfectants and reaction conditions, the characteristics of precursor structures also can influence the DBPs formation. In water treatment plants, pre-oxidation processes were developed to degrade the organic and inorganic pollutants in water, and advanced oxidation processes (AOPs) are used to degrade the trace persistent organic contaminants. In this study, for organic nitrogenous precursors include imidazole, metronidazole, benzalkonium chloride (BKC), and metformin were selected as the model compounds to investigate the characteristics of their DBP formation potential after chlorination, ozonation, or UV/ H2O2 photolysis. The correlations between the precursors (NPDOC, DON, DMA, UVScan) and their carbonaceous DBPs (THMs, HKs) and nitrogenous DBPs (HANs, TCNM, and NDMA) were analyzed. It was found that BKC is a prominent C- and N-DBPs precursor regardless of pre-oxidation or not. After ozonation and UV/H2O2 treatment, DCAN formation potential of BKC was reduced and its NDMA formation potential was increased with the reaction time. Ozonation was not effective to reduce the DBPFPs, and the DBPs yield was increased when the selected model compounds were ozonated. Imidazole, which has a heterocyclic ring and two nitrogen atoms, was not disadvantageous to form trichloro-DBPs. After pretreated with the three pre-oxidation processes, it was observed that TCNM is the prominent N-DBP.
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