Investigation of pharmaceuticals in a conventional wastewater treatment plant: Removal efficiency, seasonal variation and impact of a nearby hospital

Abstract

Discharges from the wastewater treatment plants (WWTPs) are among the main sources of contamination to receiving surface water, therefore the quality of treated wastewater needs to be properly monitored. However, not only the effluents of larger WWTPs employing advanced treatment processes have been considered, but also those from more conventional WWTPs. In this study, the occurrence and behavior of pharmaceuticals have been investigated in a conventional WWTP which receives wastewater from an urban area and a near-by hospital. 24-h composite samples were collected during one week before (influent wastewater, IWW) and after (effluent wastewater, EWW) treatment along three monitoring campaigns distributed over one year. Moreover, seven daily IWW samples discharged from a hospital were also collected. A preliminary wide-scope screening using liquid chromatography (LC) coupled to high resolution mass spectrometry allowed to identify a wide number of pharmaceuticals in the samples. Based on the screening findings, a list of 40 compounds was established for subsequent target quantitative analyses by LC-tandem mass spectrometry. Up to 75% of the compounds investigated were present in all wastewater samples. Analyte concentrations in hospital discharge samples were significantly higher, evidencing an important contribution in terms of pharmaceuticals content. Antibiotics showed the highest concentrations during the winter season, which could be related to the increase in the prescription of these compounds to treat respiratory infections. Data from this work show that the biological treatment applied was able to eliminate nearly half of the compounds under study, although still 12 pharmaceuticals were not or poorly removed.