School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore, 639798, Singapore.
Department of Environment and Energy, Sejong University, Seoul 05006, Republic of Korea.
J Environ Manage. 2019 May 1;237:629-635. doi: 10.1016/j.jenvman.2019.02.043. Epub 2019 Mar 6.
Chlorhexidine (CHX) is a broad-spectrum antimicrobial, which may pose environmental health risks. This study examined the removal potential and the mechanisms regulating the fate of CHX in activated sludge (AS). Bioreactors inoculated with AS removed 74 ± 8% and 81 ± 6% of CHX at steady state while receiving 0.5 and 1 mg/L CHX, respectively. Analysis of the removal pathways showed that biosorption, rather than biological breakdown or other abiotic losses, largely (>70%) regulated the removal of CHX. 16S rRNA gene-based analysis revealed that CHX selected for Luteolibacter (4.3-10.1-fold change) and Runella (6.2-14.1-fold change) with potential multi-drug resistance mechanisms (e.g., efflux pumps). In contrast, it significantly reduced core members (Comamonadaceae and Flavobacteriaceae) of AS, playing a key role in contaminant removal and floc formation directly associated with the performance of WWTPs (e.g., wastewater effluent quality). Antimicrobial susceptibility testing showed that 0.4-1.3 mg/L of CHX can be sublethal to AS. Our work provided new insights into the fate of CHX in urban waste streams and the potential toxicity and effects on the structure and function of AS, which has practical implications for the management of biological WWTPs treating CHX.
洗必泰（CHX）是一种广谱抗菌剂，可能对环境健康构成威胁。本研究考察了活性污泥（AS）中 CHX 的去除潜力及其调控机制。接种 AS 的生物反应器在稳态下分别以 0.5 和 1 mg/L 的 CHX 处理时，去除了 74±8%和 81±6%的 CHX。去除途径分析表明，生物吸附而不是生物降解或其他非生物损失，在很大程度上（>70%）调控了 CHX 的去除。基于 16S rRNA 基因的分析表明，CHX 选择了具有多药耐药机制（如外排泵）的黄杆菌（Luteolibacter）（4.3-10.1 倍变化）和噬夏孢菌（Runella）（6.2-14.1 倍变化）。相比之下，它显著减少了 AS 的核心成员（Comamonadaceae 和 Flavobacteriaceae），这些成员在污染物去除和与 WWTP 性能直接相关的絮体形成中发挥着关键作用（例如，废水出水质量）。抗菌敏感性测试表明，0.4-1.3 mg/L 的 CHX 对 AS 可能是亚致死的。我们的工作为 CHX 在城市废水中的命运以及对 AS 的结构和功能的潜在毒性和影响提供了新的见解，这对管理处理 CHX 的生物 WWTP 具有实际意义。
