Method Development for the Occurrence of Residual Antibiotics in Drinking Water

摘要

After extensive development, evaluation, and validation of analytical methodologies for the quantitation of antibiotics in environmental waters, samples of raw and finished water from several drinking water plants within the NCUWC were analyzed for 22 antibiotic residues. The results of these analyses provide the first snapshot of antibiotic occurrence in intakes for drinking water plants in North Carolina. The levels mirror those concentrations found in studies carried out by the U.S. Geological Survey (USGS) in other parts of the United States-albeit at lower concentrations in our study but surprising in the consistency with which specific antibiotics were found. Ciprofloxacin occurred and most frequently in retrospect, this might be expected because this drug is now more heavily prescribed as a broad-screen antibiotic. As a potent drug, Ciprofloxacin is expected to survive conventional wastewater treatment and persist to some degree in the environment. The parts-per-trillion levels found in surface waters, while extremely low due to a combination of dilution effects and adsorption onto sediments, are of concern as they indicate prevalence in other parts of the environment. Moreover, the discovery of these residues in source waters that utility managers hitherto expected to find no documented upstream discharges is troubling as it points to possibility of non-point sources such as those suggested above as non-trivial contributors to the pollutant load. This study also provided the first occurrence data of antibiotic residues in finished drinking waters in North Carolina. The trends for each treatment plant, while indicating some degree of removal during drinking water treatment, indicate that removal is not always consistent and that conventional treatment may not protect the consumer against daily exposure to low levels of these and other so-called 'emerging' contaminants.