National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing, 100124, China.
National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing, 100124, China.
Environ Pollut. 2020 Aug;263(Pt B):114508. doi: 10.1016/j.envpol.2020.114508. Epub 2020 Apr 3.
Antibiotic resistance genes (ARGs) and mobile gene elements (MGEs), the emerging genetic contaminants, are regarded as severe risks to public health for impairing the inactivation efficacy of antibiotics. Secondary effluents from wastewater treatment plants are the hotspots for spreading these menaces. Herein, sulfidated nanoscale zero-valent iron (S-nZVI) was occupied to remove ARGs and MGEs in secondary effluents and weaken the regrowth capacity of their bacterial carriers. The effects of S/Fe molar ratios (S/Fe), initial pH and dosages on 16S rRNA and ARGs removal were also investigated. Characterization, mass balance and scavenging experiments were conducted to explore the mechanisms of the gene removal. Quantitative PCR (qPCR) and high throughput fluorescence qPCR showed more than 3 log unit of 16S rRNA and seven out of 10 ARGs existed in secondary effluent could be removed after S-nZVI treatment. The mechanisms might be that DNA accepted the electron provided by the Fe core of S-nZVI after being adsorbed onto S-nZVI surface, causing the decrease of 16S rRNA, ARGs and lost their regrowth capacity, especially for typical MGE (intI1) and further inhibiting the vertical gene transfer (VGT) and intI1-induced horizontal gene transfer (HGT). Fe core was oxidized to iron oxides and hydroxides at the same time. High throughput sequencing, network analysis and variation partitioning analysis revealed the complex correlations between bacteria and ARGs in secondary effluent, S/Fe could directly influence ARGs variations, and bacterial genera made the greatest contribution to ARGs variations, followed by MGEs and operational parameters. As a result, S-nZVI could be an available reductive approach to deal with bacteria and ARGs.
抗生素抗性基因 (ARGs) 和移动基因元件 (MGEs) 作为新兴的遗传污染物，由于削弱了抗生素的灭活效果，被认为是对公众健康的严重威胁。污水处理厂的二级出水是这些威胁传播的热点。在此，负载硫化纳米零价铁 (S-nZVI) 被用于去除二级出水中的 ARGs 和 MGEs，并削弱其细菌载体的再生能力。还研究了 S/Fe 摩尔比 (S/Fe)、初始 pH 值和剂量对 16S rRNA 和 ARGs 去除的影响。通过特征分析、质量平衡和清除实验来探究基因去除的机制。定量聚合酶链式反应 (qPCR) 和高通量荧光 qPCR 表明，经过 S-nZVI 处理后，二级出水中存在的 16S rRNA 和 10 个 ARGs 中有 7 个可被去除 3 个对数单位以上。其机制可能是 16S rRNA、ARGs 及其丧失再生能力，特别是典型的 MGE (intI1)，是因为 DNA 被吸附到 S-nZVI 表面后接受了 S-nZVI 铁核提供的电子，进一步抑制垂直基因转移 (VGT) 和 intI1 诱导的水平基因转移 (HGT)。与此同时，Fe 核被氧化为铁氧化物和氢氧化物。高通量测序、网络分析和变分分区分析揭示了二级出水中细菌和 ARGs 之间复杂的相关性，S/Fe 可以直接影响 ARGs 的变化，细菌属对 ARGs 的变化贡献最大，其次是 MGEs 和操作参数。因此，S-nZVI 可以作为一种有效的还原方法来处理细菌和 ARGs。
