Occurrence and Risk Assessment of Four Typical Fluoroquinolone Antibiotics in Raw and Treated Sewage and in Receiving Waters in Hangzhou, China

A sensitive liquid chromatography-fluorescence detection method, combined with one-step solid-phase extraction, was established for detecting the residual levels of the four typical fluoroquinolone antibiotics (ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) in influent, effluent, and surface waters from Hangzhou, China. For the various environmental water matrices, the overall recoveries were from 76.8 to 122%, and no obvious interferences of matrix effect were observed. The limit of quantitation of this method was estimated to be 17 ng/L for ciprofloxacin and norfloxacin, 20 ng/L for ofloxacin, and 27 ng/L for enrofloxacin. All of the four typical fluoroquinolone antibiotics were found in the wastewaters and surface waters. The residual contents of the four typical fluoroquinolone antibiotics in influent, effluent, and surface water samples are 108-1405, 54-429, and 7.0-51.6 ng/L, respectively. The removal rates of the selected fluoroquinolone antibiotics were 69.5 (ofloxacin), 61.3 (norfloxacin), and 50% (enrofloxacin), indicating that activated sludge treatment is effective except for ciprofloxacin and necessary to remove these fluoroquinolone antibiotics in municipal sewage. The risk to the aquatic environment was estimated by a ratio of measured environmental concentration and predicted no-effect concentration. At the concentrations, these fluoroquinolone antibiotics were found in influent, effluent, and surface waters, and they should not pose a risk for the aquatic environment.