Environmental aspects of UV-C-based processes for the treatment of oxytetracycline in water

Abstract

This study is focused on oxytetracycline (OTC) degradation by direct photolysis (UV-C) and photobased advanced oxidation processes (AOPs) (UV-C/H₂O₂ and UV-C/S₂O₈^2-). OTC degradation pathways were revealed by LC-MS/MS and GC-MS/MS analyses. The evolution/degradation profiles of 12 detected byproducts were correlated with changes in biodegradability and toxicity toward Vibrio fischeri recorded during the treatment. Both photobased AOPs yielded higher OTC degradation and mineralization rates than direct photolysis. The OTC degradation pathway was found to be rather specific regarding the main reactive species (HO• or SO₄•^-)/mechanism, yielding different patterns in toxicity changes, while biodegradability profiles were less affected. Biodegradability was correlated with the observed degradation and mineralization kinetics. The recorded toxicity changes indicate that byproducts formed by initial OTC degradation are more toxic than the parent pollutant. The prolonged treatment resulted in the formation of byproducts that contributed to a decrease in toxicity and an increase in biodegradability, as particularly emphasized in the case of UV-C/S₂O₈^2-.

Keywords: Biodegradability; Byproducts; Oxytetracycline; Toxicity; UV-C-Based processes.