Antibiotic residues and endocrine disrupting compounds in municipal wastewater treatment plants in Rome, Italy

Endocrine disrupting compounds (EDCs)and pharmaceutical residues are environmental ubiquitous contaminants of particular concern due to their possible ecotoxicological effects on aquatic ecosystems. In this work, the occurrence and fate of six antibiotics (amoxicillin, ciprofloxacin, tylosin, erithromycin, sulfamethoxazole and chlortetracycline)and four phenolic endocrine disrupting compounds (EDCs, i.e. bisphenol A, 4-nonylphenol, nonylphenol mono- and di-ethoxylate)in the influents and effluents of the principal wastewater treatment plants (WWTPs)serving the city of Rome (Italy)were investigated. The aim of the study was to provide information on the persistence of the selected contaminants in the urban WWTPs, to evaluate the removal efficiencies of the investigated plants and to perform a preliminary assessment of the potential ecological risk due to the discharge through the effluents of the residual pollutants into the receiving river waters. The analytes were extracted/concentrated from 24-h composite wastewater samples by solid phase extraction (SPE), and the analytical determination was carried out by HPLC MS-MS for the antibiotics and by HPLC-fluorescence detection for the EDCs. All the contaminants were detected both in the inlet and outlet samples of the WWTPs investigated, with the only exception of the antibiotics tylosin and erythromycin. Overall, the results confirmed that the biological treatments were not able to completely remove either the antibiotic residues or the phenolic EDCs selected with removal efficiencies varying widely in the range 17-96%. As a consequence, concentration values in the effluents ranged from 6 to 897 ng/L for antibiotics and from 0.4 to 205 ng/L for phenolic EDCs, with the highest concentrations detected for chlortetracycline and amoxicillin. Indeed, the highest mass loads (mg/d/1000 inhabitants)discharged daily into the receiving waters were found for these latter antibiotics, probably due to their greater consumption by the resident population, while the lowest removal efficiencies in the WWTPs overall were found for sulfamethoxazole and ciprofloxacin, which thus proved to be the most persistent antibiotics in secondary wastewater treatments. Among the EDCs, bisphenol A and nonylphenol di-ethoxylate occurred at higher concentrations in the effluents, mostly in the WWTPs collecting a mix of urban and industrial wastes. The preliminary environmental risk analysis indicated that, although a dilution of the contaminants could potentially occur, an ecotoxicological risk, once they were in the receiving waters, could not be excluded, especially for the antibiotic residues, while it was found that for the phenolic EDCs the risk for the aquatic environment was quite minor.