Fluoroquinolones antimicrobials are partially excreted in natura after administration. Their occurrence was investigated in hospital raw sewage (HRS) and treated wastewater (TW) using an online solid phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry method (SPE-UHPLC-MS/MS). The analytical curves ranged from 0.25 to 46 ng mL-1 and the matrix effect, assessed for marbofloxacin and lomefloxacin, ranged from –63 to +1%. All HRS samples contained ciprofloxacin (1-34 ng mL-1) and ofloxacin (0.9-27 ng mL-1), while norfloxacin was detected in 17% of the samples (0.8-4.4 ng mL-1). Only ciprofloxacin (0.5-5.6 ng mL-1) was detected in TW samples. The antimicrobial activity of the HRS samples for E. coli was higher than a ciprofloxacin solution of 1 mg L-1, due to the presence of other antimicrobial agents. Ozonation (10 mg O3 L-1 min-1 ; 10 min) degraded up to 84% of the fluoroquinolones and removed the antimicrobial activity of HRS samples.

Flumequine degradation by electrochemical and photo-electrochemical processes was evaluated in this study. The antimicrobial activity of the solutions subjected to the electrochemical processes was monitored during the assays. The experiments were carried out using DSA® (dimensionally stable anode) electrode. The influence of current density was investigated for the 7.5 to 45 mA cm-2 range. The photo-electrochemical process was more efficient for degrading flumequine (85%) and reducing solution antimicrobial activity. For both processes, the residual antimicrobial activity decreased as flumequine degradation increased. The reaction intermediate m/z 244 (5-methyl-1-oxo-6,7-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-2-carboxylic acid) was identified.

In this review, the presence of quinolones in the environment, their risks and the available processes for water decontamination were addressed. Their occurrence in surface waters and also in soil raises concerns about the risk of the development of resistant bacteria and other potential chronic effects. AOPs (UV/H2O2, Fenton, photo-Fenton, and UV/TiO2) and ozonation proved effective for degrading these emerging contaminants due to hydroxyl radical formation, surpassing the efficacy of conventional methods. In addition, the main degradation mechanisms of these drugs as well as data on residual biological activity were analyzed.