Degradation and changes in toxicity and biodegradability of tetracycline during ozone/ultraviolet-based advanced oxidation

Advanced oxidation processes (AOPs) composed of O₃, H₂O₂ and ultraviolet (UV) were applied to degrade tetracycline (TC). Degradation efficiency was evaluated in terms of changes in absorbance (ABS) and total organic carbon (TOC). The change in biotoxicity was monitored with Escherichia coli and Vibrio fischeri. The improvement in biodegradability during oxidation was demonstrated through 5-day biochemical oxygen demand/chemical oxygen demand ratio and aerobic biological treatment. The combination of O₃/H₂O₂/UV and O₃/UV showed the best performance for the reductions in ABS and TOC. However, mineralization and detoxification were not perfect under the experimental conditions that were used in this study. Therefore, for the ultimate treatment of TC compounds, it is suggested that AOP treatment is followed by biological treatment, utilizing enhanced biodegradability. In this study, aerobic biological treatment by Pseudomonas putida was performed for O₃/UV-treated TC. It was confirmed that O₃/UV treatment improved TOC reduction and facilitated complete mineralization in biological treatment.