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)-O-& BULL;) 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)-O-& BULL; was produced by & gamma;-irradiation under conditions when it had a high yield. The (OH)-O-& BULL; dosage dependencies of chemical (COD) and biochemical (BOD) oxygen demands, total organic carbon (TOC) content, oxygen uptake rate (OUR), Microtox(& REG;) toxicity, and antibacterial activity values were evaluated. (OH)-O-& BULL; effectively oxidized and mineralized ofloxacin; both processes were observed even at the lowest (OH)-O-& BULL; dosage, 0.14 mmol dm(-3) (0.5 kGy absorbed dose). When 0.28 mmol dm(-3 & BULL;)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)-O-& BULL; radicals. The products did not have antibacterial activity and showed little toxicity toward the test organism Vibrio fischeri. (OH)-O-& BULL; preferentially attacks the pharmacophore part, the 4-quinolone unit of ofloxacin. (OH)-O-& BULL;-induced reactions can be safely applied to destroy the antimicrobial potency of fluoroquinolone-type antibiotics in purified wastewater matrices.