Occurrence and dissipation of veterinary antibiotics in two typical swine wastewater treatment systems in east China.

The occurrence and dissipation of 14 selected antibiotics comprising tetracyclines, sulfonamides, macrolides, fluoroquinolones, and chloramphenicols were investigated in two swine wastewater treatment systems in east China in three sampling surveys. The compounds were extracted from wastewater samples by solid-phase extraction and analyzed by ultra-performance liquid chromatography coupled with tandem mass spectrometry. The aqueous samples were unavoidably contaminated with antibiotics and the target antibiotics present in high contaminations were tetracycline, oxytetracycline, chlortetracycline, doxycycline, and sulfadiazine, with maximum concentrations of the individual contaminants reaching 41.6 × 10(3), 23.8 × 10(3), 13.7 × 10(3), 685.6 × 10(3), and 98.8 × 10(3) ng/l, respectively. The concentration ranges of these compounds were in the same order of magnitude as previously reported values in China and elsewhere. Biological activity can significantly degrade the contaminants but showed low efficiencies of dissipation of other analytes at lower levels of contamination. The removal efficiencies varied for different compounds and depended on their physiochemical properties and the treatment processes utilized at each waste treatment plant. Some target antibiotics were present in feeds obtained from swine farms at a range of average concentrations between 0.1 and 46.8 μg/kg. However, the extremely high levels of the main contaminants found in these wastewaters cannot be ascribed solely to the pattern of consumption of prescription feeds.