Ionizing Radiation Induced Removal of Ofloxacin, Abatement of Its Toxicity and Antibacterial Activity in Various Water Matrices.

The fluoroquinolone-type antibiotic ofloxacin is regularly detected in wastewaters. In this work, its hydroxyl radical (^•OH) induced degradation was studied at a concentration of 0.1 mmol dm⁻³ in three water matrices, pure water, tap water, and purified wastewater (collected from a wastewater treatment plant). ^•OH was produced by γ-irradiation under conditions when it had a high yield. The ^•OH dosage dependencies of chemical (COD) and biochemical (BOD) oxygen demands, total organic carbon (TOC) content, oxygen uptake rate (OUR), Microtox^® toxicity, and antibacterial activity values were evaluated. ^•OH effectively oxidized and mineralized ofloxacin; both processes were observed even at the lowest ^•OH dosage, 0.14 mmol dm⁻³ (0.5 kGy absorbed dose). When 0.28 mmol dm^−3 •OH was introduced into pure or tap water, the antibacterial activity vanished. In purified wastewater, a higher dosage (0.56 mmol dm⁻³) was required to achieve the same effect as in pure water, due to the organic molecules of the matrix that quenched the ^•OH radicals. The products did not have antibacterial activity and showed little toxicity toward the test organism Vibrio fischeri. ^•OH preferentially attacks the pharmacophore part, the 4-quinolone unit of ofloxacin. ^•OH-induced reactions can be safely applied to destroy the antimicrobial potency of fluoroquinolone-type antibiotics in purified wastewater matrices. [ABSTRACT FROM AUTHOR]