Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
School of Environmental Science and Engineering, Qingdao University, Qingdao 266071, China.
Water Res. 2021 Dec 1;207:117795. doi: 10.1016/j.watres.2021.117795. Epub 2021 Oct 25.
Due to the wide-presence of organic amines in natural waters, organic chloramines are commonly formed during (pre-)chlorination. With the increasing application of UV disinfection in water treatment, both the activation mechanism of organic chloramine by UV photolysis and its subsequent impact on water quality are not clear. Using sarcosine (Sar) as an amine group-containing compound, it was found that organic chloramines (i.e., Cl-Sar) would be firstly formed during chlorination even in the presence of natural organic matter. Compared with self-decay of Cl-Sar, UV photolysis accelerated Cl-Sar decomposition and induced NCl bond cleavage. Using metoprolol (MTP) as a model micro-pollutant, UV-activated Cl-Sar (UV/Cl-Sar) can accelerate micro-pollutant degradation, attributed to reactive radicals formation. HO and Cl were important contributors, with a total contribution of 45%‒64%. Moreover, the degradation rate of MTP by UV/Cl-Sar was pH-dependent, which monotonically increased from 0.044 to 0.065 min under pHs 5.5‒8.5. Although the activation of organic chloramine by UV could accelerate micro-pollutant degradation, UV/Cl-Sar treatment could also enhance disinfection by-products formation. Trichloromethane (TCM) formation was observed during MTP degradation by UV/Cl-Sar. After post-chlorination, TCM, 1,1-dichloropropanone, 1,1,1-trichloropropanone, and dichloroacetonitrile were detected. Their individual and total concentrations were all positively proportional to UV/Cl-Sar treatment time. The total concentration with 30 min treatment (66.93 μg L) was about 2.3 times that with 1 min treatment (28.76 μg L). Finally, the accelerated effect was verified with Cl-glycine and Cl-alanine. It is expected to unravel the non-negligible role of organic chloramine on water quality during UV disinfection.
由于有机胺在天然水中广泛存在，因此在（预）氯化过程中通常会形成有机氯胺。随着紫外线消毒在水处理中的应用不断增加，有机氯胺通过紫外线光解的活化机制及其对水质的后续影响尚不清楚。使用肌氨酸（Sar）作为含胺基的化合物，研究发现，即使存在天然有机物，氯化过程中也会首先形成有机氯胺（即 Cl-Sar）。与 Cl-Sar 的自分解相比，紫外线光解加速了 Cl-Sar 的分解并诱导了 NCl 键的断裂。以美托洛尔（MTP）为模型微量污染物，UV 激活的 Cl-Sar（UV/Cl-Sar）可以加速微量污染物的降解，这归因于活性自由基的形成。HO 和 Cl 是重要的贡献者，总贡献为 45%‒64%。此外，UV/Cl-Sar 处理对 MTP 的降解速率受 pH 值影响，在 pH 值为 5.5‒8.5 时，从 0.044 到 0.065 min 单调增加。尽管紫外线对有机氯胺的活化可以加速微量污染物的降解，但 UV/Cl-Sar 处理也会增强消毒副产物的形成。在 UV/Cl-Sar 处理下 MTP 降解过程中观察到三氯甲烷（TCM）的形成。在 MTP 降解后进行氯化，检测到三氯甲烷、1,1-二氯丙酮、1,1,1-三氯丙酮和二氯乙腈。它们的个体和总浓度都与 UV/Cl-Sar 处理时间呈正相关。30 min 处理（66.93μg/L）的总浓度约为 1 min 处理（28.76μg/L）的 2.3 倍。最后，用 Cl-甘氨酸和 Cl-丙氨酸验证了加速效应。这有望揭示紫外线消毒过程中有机氯胺对水质的不可忽视作用。
