The occurrence and removal of selected fluoroquinolones in urban drinking water treatment plants

Fluoroquinolones (FQs) are a widely prescribed group of antibiotics. They enter the aqueous environment, where they are frequently detected, and can lead to a threat to human health. Drinking water treatment plants (DWTPs) play a key role in removing FQs from potable water. This study investigated the occurrence and removal of four selected FQs (norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL)) in three urban DWTPs in China. The treatment efficacy for each system was simultaneously evaluated. Two of the examined DWTPs used conventional treatment processes. The third used conventional processes followed by additional treatment processes (ozonation-biologically activated carbon (ozonation-BAC) and membrane technology). The average concentrations of the four FQs in the source water and the finished water ranged from 51 to 248 ng/L and from <5 to 46 ng/L, respectively. Based on residual concentrations, the conventional treatment system had a low removal of FQs. In contrast, the addition of advanced treatment processes such as the ozonation-BAC and membranes, substantially improved the removal of FQs. The finding of this study has important implications: even though coagulation-sedimentation and chlorination treatment processes can remove most target FQs, the typical practice of advanced treatment processes is necessary for the further removal.