Fate of antibiotics from hospital and domestic sources in a sewage network.

Investigation of domestic and hospital effluents in a sewage system of an elementary watershed showed that antibiotics belonging to eight classes were present with concentrations ranging from <LOQ to 50μgL-1. The compounds most often detected in the effluents were the fluoroquinolones (79-100%), the sulfonamides (86-100%) and the macrolides (79-86%). Vancomycin, strictly reserved for hospital use in France, was detected exclusively in the hospital effluent, supporting its pertinent use as a marker of hospital discharge. Beta-lactams, which are among the most frequently consumed compounds, were rarely detected in the effluents, due to their rapid hydrolysis. Out of 23 antibiotics used in veterinary and human medicine, fourteen were quantified in both the wastewater treatment plant (WWTP) input and output: erythromycin, amoxicillin, tetracycline, trimethoprim, ormethoprim, sulfamethoxazole, vancomycin and seven quinolones (flumequine, enrofloxacin, enoxacin, ofloxacin, lomefloxacin, norfloxacin and ciprofloxacin). Antibiotic concentrations in the hospital effluent (from 0.04 to 17.9μgL-1) were ten times higher than those measured in the domestic effluent (from 0.03 to 1.75μgL-1), contributing to 90% of the antibiotic inputs to the WWTP. Some molecules such as sulfamethoxazole, erythromycin and trimethoprim displayed higher concentrations after wastewater treatment due to deconjugation of their metabolites, which restores the parent molecules. For other compounds, the antibiotic elimination showed discrepancies depending on their physicochemical properties. For fluoroquinolones, the apparent removal processes were mainly based on adsorption mechanisms, followed by settling, leading to sludge contamination (from 13 to 18,800μgkg-1 dry weight).