School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P.R. China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P.R. China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, Guangdong, P.R. China.
Water Res. 2020 Nov 1;186:116313. doi: 10.1016/j.watres.2020.116313. Epub 2020 Aug 18.
Chlorine dioxide (ClO) can be used as a pre-oxidant when chloramination is performed in water treatment plants. However, the effects of ClO pre-oxidation on the formation of nitrogenous disinfection by-products, such as dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm), during chloramination are not well understood. In this study, the effects of ClO pre-oxidation on the formation of DCAN and DCAcAm during chloramination of 28 model compounds and seven real water samples were investigated. The sources of nitrogen for DCAN and DCAcAm formation were investigated using N-labeled monochloramine. ClO pre-oxidation affected DCAN and DCAcAm formation during chloramination of model compounds in different ways. ClO pre-oxidation increased unlabeled and N-labeled DCAN and DCAcAm formation during chloramination of six amino acids and peptides and five indoles and tertiary amines. ClO pre-oxidation decreased DCAN formation but increased DCAcAm formation during chloramination of three hydroxybenzamide compounds, but had the opposite effects for four tetracyclines. ClO pre-oxidation generally decreased DCAN and DCAcAm formation during chloramination of the phenolic compounds that are precursors not containing nitrogen. 2-Aminoacetophenone, formamid-trans-muconic acid, and unsaturated ketones were found to be transformation products of ClO oxidation of 3-methylindole, salicylamide, and resorcinol, respectively. Possible DCAN and DCAcAm formation pathways during chloramination after ClO oxidation were identified. For most of the water samples, ClO pre-oxidation decreased the amounts of DCAN and DCAcAm formed during chloramination by 36%-70% and 11%-59%, respectively. This may have been caused by ClO oxidation destroying phenolic precursors and macromolecular proteins rather than amino acids in the water samples.
二氧化氯 (ClO) 可用作水处理厂进行氯胺化时的预氧化剂。然而，ClO 预氧化对氯胺化过程中氮消毒副产物（如二氯乙腈 (DCAN) 和二氯乙酰胺 (DCAcAm)）形成的影响尚不清楚。在这项研究中，研究了 ClO 预氧化对 28 种模型化合物和 7 种实际水样在氯胺化过程中形成 DCAN 和 DCAcAm 的影响。使用 N 标记的一氯胺研究了 DCAN 和 DCAcAm 形成的氮源。ClO 预氧化以不同的方式影响模型化合物在氯胺化过程中 DCAN 和 DCAcAm 的形成。ClO 预氧化增加了六种氨基酸和肽以及五种吲哚和叔胺在氯胺化过程中未标记和 N 标记的 DCAN 和 DCAcAm 的形成。ClO 预氧化降低了三种羟基苯甲酰胺化合物在氯胺化过程中的 DCAN 形成，但增加了 DCAcAm 的形成，但对四种四环素则相反。ClO 预氧化通常降低了不含氮前体的酚类化合物在氯胺化过程中 DCAN 和 DCAcAm 的形成。发现 3-甲基吲哚、水杨酰胺和间苯二酚的 ClO 氧化产物分别为 2-乙酰苯酮、反式-富马酸酰胺和不饱和酮。鉴定了 ClO 氧化后氯胺化过程中 DCAN 和 DCAcAm 形成的可能途径。对于大多数水样，ClO 预氧化使氯胺化过程中形成的 DCAN 和 DCAcAm 分别减少了 36%-70%和 11%-59%。这可能是由于 ClO 氧化破坏了水样中的酚类前体和大分子蛋白质，而不是氨基酸。
