Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, College of Civil Engineering, Hunan University, Changsha, Hunan, 410082, PR China.
Brook Byer Institute for Sustainable Systems and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
Water Res. 2021 Feb 15;190:116708. doi: 10.1016/j.watres.2020.116708. Epub 2020 Nov 30.
It is well known that using chlorine dioxide (ClO) as a disinfectant inevitably produces a common disinfection byproducts chlorite (ClO). In this study, we found that UV photolysis after ClO disinfection can effectively eliminate both ClO and contaminants of emerging concern (CECs). However, the kinetic mechanisms of UV/ClO process destructing CECs, as well as transformation of ClO in UV/ClO system are not clear yet. Therefore, we systematically investigated the UV/ClO system to assist us appropriately design this process under optimal operational conditions. In this work, we first investigated the impact of water matrix conditions (i.e., pH, bicarbonate and natural organic matter (NOM)) and ClO dosage on the UV/ClO process. We found that bicarbonate and NOM have inhibition effects, while lower pH and higher ClO dosage have enhancement effects. Besides, hydroxyl radical (HO) and reactive chlorine species (RCS) are generated from UV/ClO system, and RCS are main contributors to CBZ degradation. Then we proposed a possible degradation pathway of CBZ based on the determined products from experiments. Additionally, we found that photolysis of ClO resulted in the generation of chloride (Cl) and chlorate (ClO). As the ClO dosage increases, the yield of ClO increased while that of Cl decreased. Finally, we elucidated the second order rate constant of the target organic compound with HO• has a strong correlation with the formation of ClO.
众所周知，使用二氧化氯（ClO）作为消毒剂不可避免地会产生常见的消毒副产物亚氯酸盐（ClO）。在本研究中，我们发现 ClO 消毒后的紫外线光解可以有效地消除 ClO 和新兴关注污染物（CECs）。然而，UV/ClO 工艺破坏 CECs 的动力学机制以及 UV/ClO 系统中 ClO 的转化尚不清楚。因此，我们系统地研究了 UV/ClO 系统，以便在最佳操作条件下适当设计该工艺。在这项工作中，我们首先研究了水基质条件（即 pH 值、碳酸氢盐和天然有机物（NOM））和 ClO 剂量对 UV/ClO 工艺的影响。我们发现碳酸氢盐和 NOM 具有抑制作用，而较低的 pH 值和较高的 ClO 剂量具有增强作用。此外，UV/ClO 系统中生成了羟基自由基（HO）和活性氯物种（RCS），RCS 是 CBZ 降解的主要贡献者。然后，我们根据实验确定的产物提出了 CBZ 的可能降解途径。此外，我们发现 ClO 的光解导致生成了氯离子（Cl）和氯酸盐（ClO）。随着 ClO 剂量的增加，ClO 的产率增加，而 Cl 的产率降低。最后，我们阐明了与 ClO 形成具有强相关性的目标有机化合物与 HO•的二级反应速率常数。
