Advanced oxidation of quinolone antibiotics in water by ozone and the peroxone process

Quinolone antibiotics can be found in WWTP effluent and surface waters at ng.l-1 - µg.l-1 concentration range. Induction of bacterial resistance against these antibiotics and toxicity to aquatic organisms are possible adverse effects. Since quinolones are not readily biodegradable, physical chemical removal technologies are indispensable for their removal. In this work, ozonation and the peroxone process were selected as removal technologies. A first experimental part focuses on quinolone analysis. Chromatographic separation of ciprofloxacin stock solutions resulted in 2 chromatographic peaks with pH dependent peak area ratio. Next, an analytical procedure, based on SPE-LC-UV, was developed for separation of the quinolones ciprofloxacin, levofloxacin and flumequine at a concentration range of 0.03 – 45.3 µM. Ozonation of ciprofloxacin and levofloxacin is discussed in the second part of this thesis. Degradation occurred at the piperazinyl substituent and the quinolone moiety. This is mainly influenced by the parameter pH while H2O2 addition had only limited effect. For levofloxacin, approximately two times faster ozonation was observed at pH 10 compared to pH 3 and 7 while for ciprofloxacin, degradation was 25 and 10% faster at pH 3 compared to pH 7 and 10, respectively. Degradation at the piperazinyl substituent is favoured at pH 10 due to fast ozonation at the unprotonated amine of the piperazinyl substituent. At pH 7, degradation at the quinolone moiety is enhanced which results in the formation of isatin and anthranilic acid analogues. Addition of an excess t-butanol to the ozonation experiments excluded formation of these compounds, suggesting the necessity of radicals for formation of isatin and anthranalic acid analogues. This was confirmed by calculating the Fukui function for radical attack, which predicted the C2-atom of the quinolone moiety as one of the main sites for radical attack. Agar diffusion tests with P. fluorescens, E. coli and B. coagulans for ozonated quinolone samples in deionized water revealed that ozonation efficiently reduces antibacterial activity, related to the parent compound degradation rate. In hospital WWTP effluent, however, degradation products affect the residual antibacterial activity against B. coagulans. The ciprofloxacin degradation rate in hospital WWTP effluent was influenced by sorption