Department of Environmental Engineering, Kangwon National University, Chuncheon 24341, Republic of Korea.
Department of Chemical Engineering, McGill University, 3610 University St., Montréal H3A 0C5, Québec, Canada.
Sci Total Environ. 2023 Jan 15;856(Pt 1):159076. doi: 10.1016/j.scitotenv.2022.159076. Epub 2022 Sep 28.
Tetracyclines are one of the antibiotics widely employed worldwide and frequently detected in surface waters because of incomplete removal from wastewater treatment. Various advanced oxidation processes have been investigated for tetracyclines degradation and their transformation products (TPs) have recently gained more attention. Studies on ozonation are however seldom for the degradation of oxytetracycline (OTC) and doxycycline (DTC). In the present study, a lower O inlet gas concentration (4.67 ± 0.13 mg/L), supplied at a flow rate of 0.27 L/min, was shown to be more effective at removing OTC than the same dose of ozone applied at higher inlet gas concentration (up to 6.29 mg/L) over a shorter time at the same flow rate. The use of pCBA and t-BuOH indicated that ozone plays a more important role in the degradation of OTC than HO•. The DTC degradation was less efficient than for OTC, with 99 % removal requiring twice the amount of ozone. OTC had almost no inhibition of Vibrio fischeri, however, the inhibition ratio was increased to 37 % (5-min) and 46 % (15-min) within 1 min of ozonation. Contrastly, DTC had toxic effects on V. fischeri (inhibition rate of 84 %) and sustained toxicity in samples treated for up to 40-min. The observed toxicities after treatment could be explained by the identified TPs (26 TPs for OTC and 23 for DTC, some identified for the first time) and their quantitative structure-activity relationship analysis data. Several TPs showed toxic or extremely toxic predicted effects on fish, daphnid, and green algae, corresponding with the V. fischeri inhibition results. Among the possible degradation pathways, aromatic ring hydroxylation and ring-opening pathways could lead to the formation of TPs less harmful to the environment.
四环素是全球广泛使用的抗生素之一，由于在废水处理过程中未完全去除，因此经常在地表水中检测到。各种高级氧化工艺已被用于研究四环素的降解，其转化产物（TPs）最近受到了更多的关注。然而，关于臭氧化的研究很少涉及土霉素（OTC）和强力霉素（DTC）的降解。在本研究中，与相同剂量的较高进气浓度（高达 6.29 mg/L）相比，较低的进气气体浓度（4.67 ± 0.13 mg/L），以 0.27 L/min 的流速供应，在相同流速下，较短时间内对 OTC 的去除效果更有效。pCBA 和 t-BuOH 的使用表明，臭氧在 OTC 的降解中比 HO•更重要。DTC 的降解效率不如 OTC 高，需要两倍的臭氧量才能达到 99%的去除率。然而，OTC 对发光菌几乎没有抑制作用，但是，在臭氧化 1 分钟内，抑制率增加到 37%（5 分钟）和 46%（15 分钟）。相比之下，DTC 对发光菌（抑制率为 84%）具有毒性作用，并且在处理样品长达 40 分钟后仍具有持续毒性。处理后观察到的毒性可以用鉴定的 TPs（OTC 有 26 个 TPs，DTC 有 23 个 TPs，其中一些是首次鉴定）及其定量构效关系分析数据来解释。一些 TPs 对鱼类、水蚤和绿藻表现出有毒或极毒的预测作用，与发光菌抑制结果相对应。在可能的降解途径中，芳环羟化和开环途径可能导致形成对环境危害较小的 TPs。
