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

Advanced oxidation processes (AOPs) composed of O-3, 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 O-3/H2O2/UV and O-3/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 O-3/UV-treated TC. It was confirmed that O-3/UV treatment improved TOC reduction and facilitated complete mineralization in biological treatment.