School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, 212003, China; Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, 212003, China.
Chemosphere. 2021 Apr;268:129340. doi: 10.1016/j.chemosphere.2020.129340. Epub 2020 Dec 16.
Bromate (BrO) is a predominant undesired toxic disinfection by-product (DBP) during ozonation of bromide-containing waters. The reduction of BrO by zero valent iron (ZVI) and its effect on formation of organic halogenated DBPs during chlorination were investigated in this study. The presence of ZVI could reduce BrO to bromide (Br), and Br formed could be transformed to free bromine (HOBr/OBr) during chlorination, further leading to organic brominated (Br-) DBPs formation. Formation of DBPs during chlorination, including trihalomethanes (THMs) and haloacetonitriles (HANs) was detected under different conditions. The results showed that when ZVI dosage increased from 0 to 1 g L, the formation of Br-DBPs (e.g., TBM and DBCM) was significantly improved, while the formation of Cl-DBPs (e.g., TCM, TCAN and DCAN) reduced. Higher ZVI dosage exhibited inhibitory effect on Br-DBPs formation due to the competition between ZVI and free chlorine (HOCl/OCl). The bromine substitution factor (BSF) of THMs significantly decreased from 0.61 ± 0.06 to 0.22 ± 0.02, as the pH was raised from 5.0 to 9.0. Besides, the increase of initial BrO concentration significantly improved the formation of Br-DBPs and decreased the formation of Cl-DBPs, leading to an obvious rise on the BSF of THMs. As the initial concentration of HOCl increased, all THMs and HANs gradually increased. Moreover, the analysis based on the cytotoxicity index (CTI) of the determined DBPs showed that reduction of BrO by ZVI during chlorination had certain risks in real water sources, which should be paid attention to in the application.
溴酸盐（BrO）是含溴水在臭氧氧化过程中产生的主要有害的毒性消毒副产物（DBP）。本研究考察了零价铁（ZVI）还原 BrO 以及其对氯化过程中有机卤代 DBP 形成的影响。研究发现，ZVI 的存在可以将 BrO 还原为溴化物（Br），在氯化过程中形成的 Br 可以转化为游离溴（HOBr/OBr），进一步导致有机溴化（Br-）DBP 的形成。在不同条件下进行氯化实验，检测到 DBPs 的形成，包括三卤甲烷（THMs）和卤乙腈（HANs）。结果表明，当 ZVI 剂量从 0 增加到 1 g/L 时，Br-DBPs（如 TBM 和 DBCM）的形成显著增加，而 Cl-DBPs（如 TCM、TCAN 和 DCAN）的形成减少。由于 ZVI 和自由氯（HOCl/OCl）之间的竞争，较高的 ZVI 剂量对 Br-DBPs 的形成表现出抑制作用。THMs 的溴取代因子（BSF）显著从 0.61±0.06 降低到 0.22±0.02，随着 pH 值从 5.0 升高到 9.0。此外，BrO 初始浓度的增加显著提高了 Br-DBPs 的形成，降低了 Cl-DBPs 的形成，导致 THMs 的 BSF 明显上升。随着初始 HOCl 浓度的增加，所有 THMs 和 HANs 逐渐增加。此外，基于所测定 DBPs 的细胞毒性指数（CTI）的分析表明，氯化过程中 ZVI 还原 BrO 具有一定的实际水源风险，在应用中应予以关注。
