Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zürich, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
Water Res. 2018 Oct 1;142:267-278. doi: 10.1016/j.watres.2018.05.045. Epub 2018 May 25.
Ozonation and subsequent post-treatments are increasingly implemented in wastewater treatment plants (WWTPs) for enhanced micropollutant abatement. While this technology is effective, micropollutant oxidation leads to the formation of ozonation transformation products (OTPs). Target and suspect screening provide information about known parent compounds and known OTPs, but for a more comprehensive picture, non-target screening is needed. Here, sampling was conducted at a full-scale WWTP to investigate OTP formation at four ozone doses (2, 3, 4, and 5 mg/L, ranging from 0.3 to 1.0 gO/gDOC) and subsequent changes during five post-treatment steps (i.e., sand filter, fixed bed bioreactor, moving bed bioreactor, and two granular activated carbon (GAC) filters, relatively fresh and pre-loaded). Samples were measured with online solid-phase extraction coupled to liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS) using electrospray ionization (ESI) in positive and negative modes. Existing non-target screening workflows were adapted to (1) examine the formation of potential OTPs at four ozone doses and (2) compare the removal of OTPs among five post-treatments. In (1), data processing included principal component analysis (PCA) and chemical knowledge on possible oxidation reactions to prioritize non-target features likely to be OTPs. Between 394 and 1328 unique potential OTPs were detected in positive ESI for the four ozone doses tested; between 12 and 324 unique potential OTPs were detected in negative ESI. At a specific ozone dose of 0.5 gO/gDOC, 27 parent compounds were identified and were related to 69 non-target features selected as potential OTPs. Two OTPs were confirmed with reference standards (venlafaxine N-oxide and chlorothiazide); 34 other potential OTPs were in agreement with literature data and/or reaction mechanisms. In (2), hierarchical cluster analysis (HCA) was applied on profiles detected in positive ESI mode across the WWTP and revealed 11 relevant trends. OTP removal was compared among the five post-treatments and 54-83% of the non-target features that appeared after ozonation were removed, with the two GAC filters performing the best. Overall, these data analysis strategies for non-target screening provide a useful tool to understand the behavior of unknown features during ozonation and post-treatment and to prioritize certain non-targets for further identification.
臭氧化和随后的后处理在污水处理厂（WWTP）中越来越多地被采用，以增强对微量污染物的去除。虽然这项技术很有效，但微量污染物的氧化会导致臭氧化转化产物（OTP）的形成。目标和可疑筛选提供了有关已知母体化合物和已知 OTP 的信息，但为了更全面地了解情况，需要进行非目标筛选。在这里，在一个全规模的 WWTP 中进行了采样，以研究在四个臭氧剂量（2、3、4 和 5mg/L，范围为 0.3 至 1.0gO/gDOC）下 OTP 的形成以及随后在五个后处理步骤（即砂滤、固定床生物反应器、移动床生物反应器和两个颗粒活性炭（GAC）过滤器，相对新鲜和预加载）期间的变化。使用在线固相萃取与液相色谱高分辨率串联质谱（LC-HRMS/MS）联用，采用电喷雾电离（ESI）在正、负模式下对样品进行测量。对现有的非目标筛选工作流程进行了改编，以（1）研究四个臭氧剂量下潜在 OTP 的形成，以及（2）比较五个后处理中 OTP 的去除。在（1）中，数据处理包括主成分分析（PCA）和可能的氧化反应的化学知识，以优先考虑可能是 OTP 的非目标特征。在测试的四个臭氧剂量下，在正 ESI 中检测到 394 到 1328 个独特的潜在 OTP；在负 ESI 中检测到 12 到 324 个独特的潜在 OTP。在特定的臭氧剂量为 0.5gO/gDOC 时，鉴定出 27 种母体化合物，与作为潜在 OTP 选择的 69 种非目标特征相关。用参考标准（文拉法辛 N-氧化物和氯噻嗪）确认了两种 OTP；34 种其他潜在的 OTP 与文献数据和/或反应机制一致。在（2）中，在 WWTP 中应用正 ESI 模式下检测到的图谱的层次聚类分析（HCA）揭示了 11 个相关趋势。比较了五个后处理中 OTP 的去除情况，在臭氧化后出现的 54-83%的非目标特征被去除，两个 GAC 过滤器的效果最好。总的来说，这些非目标筛选的数据分析策略为了解臭氧化和后处理过程中未知特征的行为提供了有用的工具，并为进一步鉴定确定了某些非目标。
