Department of Urban Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Sci Total Environ. 2016 Jan 1;539:165-174. doi: 10.1016/j.scitotenv.2015.08.111. Epub 2015 Sep 8.
In small reservoirs in tropical islands in Japan, the disinfection by-product formation potential is high due to elevated concentrations of dissolved organic matter (DOM) and bromide. We employed a combined method of variation of chloride concentrations and the use of DOM surrogates to investigate removal mechanisms of bromide and different fractions of DOM by chloride-based magnetic ion exchange (MIEX®) resin. The DOM in reservoir waters was fractionated by resins based on their hydrophobicity, and characterized by size-exclusion chromatography and fluorescence excitation-emission matrix spectrophotometry. The hydrophobic acid (HPO acid) fraction was found to be the largest contributor of the trihalomethane (THM) precursors, while hydrophilic acid (HPI acid) was the most reactive precursors of all the four THM species. Bromide and DOM with a molecular weight (MW) greater than 1kDa, representing HPO acid (MW 1-3kDa) and HPI acid (MW 1-2kDa), were effectively removed by MIEX® resin; however, DOM with a MW lower than 1kDa, representing HPI non-acid, was only moderately removed. The removal of THM precursors by MIEX® resin was interfered by high chloride concentrations, which was similar to the removal of glutamic acid (HPI acid surrogate) and bromide. However, elevated chloride concentrations had only a minor effect on tannic acid (HPO acid surrogate) removal, indicating that HPO acid fraction was removed by a combination of ion exchange and physical adsorption on MIEX® resin. Our study demonstrated that the combined use of DOM surrogates and elevated chloride concentrations is an effective method to estimate the removal mechanisms of various DOM fractions by MIEX® resin.
在日本热带岛屿的小型水库中，由于溶解有机物 (DOM) 和溴化物浓度升高，消毒副产物形成潜力较高。我们采用氯离子浓度变化和 DOM 替代物相结合的方法，研究了基于氯离子的磁性离子交换 (MIEX®) 树脂对溴化物和不同 DOM 分数的去除机制。利用树脂根据疏水性对水库水中的 DOM 进行了分级，并通过尺寸排阻色谱和荧光激发-发射矩阵分光光度法进行了表征。发现疏水性酸（HPO 酸）级分是三卤甲烷（THM）前体的最大贡献者，而亲水性酸（HPI 酸）是所有四种 THM 物质中最具反应性的前体。MIEX®树脂能有效去除溴化物和分子量（MW）大于 1kDa 的 DOM，代表 HPO 酸（MW 1-3kDa）和 HPI 酸（MW 1-2kDa）；然而，MW 小于 1kDa 的 DOM，代表 HPI 非酸，仅被适度去除。高氯离子浓度会干扰 THM 前体的去除，这与谷氨酸（HPI 酸替代物）和溴化物的去除相似。然而，高氯离子浓度对鞣酸（HPO 酸替代物）的去除影响较小，表明 HPO 酸级分通过 MIEX®树脂上的离子交换和物理吸附的组合方式被去除。我们的研究表明，DOM 替代物和升高的氯离子浓度的联合使用是一种有效方法，可以估计 MIEX®树脂对各种 DOM 级分的去除机制。
