Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China.
Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China; Institute of Eco-Chongming, East China Normal University, Shanghai, China.
J Environ Manage. 2019 Feb 15;232:219-225. doi: 10.1016/j.jenvman.2018.11.059. Epub 2018 Nov 23.
Triclosan (TCS) contaminant has aroused wide concerns due to the high risk of converting into toxic dioxin in aquatic environments. During the wastewater treatment process, considerable amounts of TCS are accumulated in activated sludge but the mechanisms are still unclear. Especially, roles of extracellular polymeric substances (EPS), the main components of activated sludge, in TCS removal have never been addressed. In this work, the binding properties of loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) of activated sludge to TCS are investigated by fluorescence quenching approach. The influences of aquatic conditions including solution pH, ionic strength and temperature on the interactions between EPS and TCS are explored. Possible interaction mechanisms are discussed as well as the corresponding environmental implication. Results indicate that binding processes of EPS to TCS are exothermic mainly driven by the enthalpy changes. The proteins components in EPS dominate the interactions between EPS and TCS by hydrogen bond and hydrophobic interaction. The binding strength could be improved under the condition of weak alkaline and relative high ionic strength. Generally, LB-EPS exhibit stronger binding ability to TCS than TB-EPS under neutral environment, playing more crucial roles in the binding process. This work highlights the important contributions of EPS to TCS removal, that is beneficial to comprehensively understand the migration of TCS in activated sludge system.
三氯生（TCS）污染物由于在水生环境中转化为有毒二噁英的风险较高而引起了广泛关注。在废水处理过程中，大量的 TCS 会在活性污泥中积累，但具体机制尚不清楚。特别是，活性污泥中主要成分——细胞外聚合物（EPS）在 TCS 去除中的作用尚未得到解决。在这项工作中，通过荧光猝灭法研究了活性污泥中松散结合 EPS（LB-EPS）和紧密结合 EPS（TB-EPS）与 TCS 的结合特性。探讨了包括溶液 pH 值、离子强度和温度等水相条件对 EPS 和 TCS 之间相互作用的影响。同时讨论了可能的相互作用机制以及相应的环境意义。结果表明，EPS 与 TCS 的结合过程主要是由焓变驱动的放热过程。EPS 中的蛋白质组分通过氢键和疏水相互作用主导 EPS 和 TCS 之间的相互作用。在弱碱性和相对高离子强度条件下，结合强度可以提高。一般来说，在中性环境下，LB-EPS 对 TCS 的结合能力强于 TB-EPS，在结合过程中发挥着更重要的作用。这项工作强调了 EPS 对 TCS 去除的重要贡献，有助于全面了解 TCS 在活性污泥系统中的迁移。
