State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Water Res. 2023 Sep 1;243:120328. doi: 10.1016/j.watres.2023.120328. Epub 2023 Jul 8.
Iron coagulants have been used extensively in drinking water treatment. This typically produces substantial quantities of insoluble iron hydrolysis products which interact with natural and anthropogenic organic substances during the coagulation process. Previous studies have shown that the removal of low molecular weight (MW) organics is relatively poor by coagulation, which leads to their presence during disinfection, with the formation of halogenated byproducts, and in treated water supplies as potentially biodegradable material. Currently, there is little knowledge about the changes that occur in the nature of coagulant flocs as they age with time and how such changes affect interactions with organic matter, especially low MW organics. To improve this deficiency, this study has investigated the variation of aged flocs obtained from two commonly used iron salts and their impact on representative organic contaminants, natural organic matter (NOM) and tetracycline antibiotic (TC), in a real surface water. It was found that aging resulted in increasing crystallization of the flocs, which can play a beneficial role in activating persulfate oxidant to remove the representative organics. Furthermore, acidification was also found to further improve the removal of low MW natural organics and tetracycline. In addition, the results showed that the low MW fractions of NOM (<1 K Dalton) were substantially removed by the aging flocs. These results are in marked contrast to the poor removal of low MW organic substances by conventional coagulation, with or without added oxidants, and show that aged flocs have a high potential of reuse for re-coagulation and activation of oxidants to reduce low MW organics, and enhance drinking water quality.
铁基混凝剂在饮用水处理中得到了广泛的应用。这通常会产生大量的不溶性铁水解产物，这些产物在混凝过程中会与天然和人为有机物质相互作用。先前的研究表明，混凝对低分子量（MW）有机物的去除效果相对较差，这导致它们在消毒过程中存在，形成卤代副产物，并在处理后的供水中作为潜在可生物降解的物质存在。目前，对于随着时间的推移，老化的絮体在性质上发生的变化以及这些变化如何影响与有机物，特别是低分子量有机物的相互作用，人们知之甚少。为了弥补这一不足，本研究调查了两种常用铁盐生成的老化絮体的变化及其对代表性有机污染物、天然有机物（NOM）和四环素抗生素（TC）的影响，研究对象是实际地表水中的老化絮体。结果发现，老化导致絮体结晶度增加，这对激活过硫酸盐氧化剂去除代表性有机物起到了有益的作用。此外，酸化也被发现可以进一步提高低分子量天然有机物和四环素的去除率。此外，研究结果表明，老化絮体可以大量去除 NOM 的低分子量部分(<1 K Dalton)。这些结果与传统混凝剂对低分子量有机物的去除效果形成鲜明对比，无论是否添加氧化剂，这表明老化絮体具有很高的再利用潜力，可用于再混凝和激活氧化剂，以去除低分子量有机物，提高饮用水质量。
