Investigation of Drugs in Wastewater: Removal Efficiency in a Treatment Plant and Environmental Impact Assessment

Treball Final de Grau en Química. Codi: QU0943. Curs acadèmic: 2019/2020 This study assessed the presence of 41 pharmaceuticalsin wastewater samples from the north of Spain. The samples under study were collected during a week, before the treatment (influent) and after treatment (effluent) in a wastewater treatment plant (WWTP). Additionally, samples reaching the inlet of the WWTP from hospital discharge were also collected. The wastewater samples were analysed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry using triple quadrupole analyzer (UHPLC-MS/MS QqQ) due to its greatselectivity and sensitivity. Analyses were performed by direct injection (DI) of the samples; so, pre-concentration treatments were avoided. Moreover, in order to correct matrix effects, Isotopically-Labelled Internal Standards (ILIS) available for some pharmaceuticals were added to the samples. Acetaminophen and Gabapentin were the most frequently detected compounds in both influent wastewater (IWW) and Hospital discharge. In EWW, it was observed a decrease in the concentrations of pharmaceuticals in comparison to the influent samples. The removal efficiency (RE) (%) was calculated by comparing the mass load of the influent and the effluent samples. From the 30 compounds detected in wastewater, only three pharmaceuticals (Acetaminophen, Atorvastatin and Enalapril) presented a 100% RE, which means that they were completely eliminated after passing through the WWTP. The results of this work indicate that most of pharmaceuticals under study are present in treated wastewater, and consequently they reach the aquatic environment. Hazard quotients (HQ) were calculated to assess the potential environmental risks of these pharmaceuticals. The results showed that generally there are not significant risks associated to the presence of pharmaceuticals in the aquatic environment although Ciprofloxacin, Diclofenac, Norfloxacin and Venlafaxine presented an HQ > 1 implying that the amount of these compounds released into the environment is above the non-effect concentration. The results from this study contribute to the better understanding of potential risks associated to the presence of pharmaceuticals in urban wastewater and their impact on the aquatic environment.