Occurrence of selected pharmaceuticals in wastewater treatment plants of Tuscany: An effect-based approach to evaluate the potential environmental impact.

Abstract

Municipal wastewaters may pose a risk to the aquatic environment and ultimately to human kind. Their treatment is a fundament step but the actual WWTPs performances cannot be taken for granted, claiming instead for continuous evaluation campaigns. Our waters are indeed threatened by the continuous input of various persistent micropollutants that are part of human daily routine life; the potential effects of their presence in the receiving waters have to be quantified. The present paper reports data of a monitoring campaign focused on nine pharmaceuticals belonging to different therapeutic groups in three WWTPs in Tuscany (Italy). All the three WWTPs use conventional activated sludge process with pre-denitrification and no tertiary treatment. The analytical determination has been achieved through off-line solid phase extraction and analysis in liquid chromatography coupled with mass spectrometry. The overall ecotoxicological effect of effluents was evaluated through a battery of tests using organisms belonging to different trophic levels. All nine pharmaceuticals were detected in the influent of all WWTPs at least in one sampling campaign. The most concentrated compounds were acetaminophen, diclofenac and amoxicillin followed by atenolol, ketoprofen, clarithromycin, carbamazepine, doxycycline and E2; their average concentrations (considering all measurements from all plants) were, respectively: 3914 ± 2620; 2065 ± 739; 2002 ± 2170; 1223 ± 1042; 961 ± 1003; 356 ± 370; 233 ± 100; 196 ± 189; 4 ± 4 ng/L. The highest concentrations were found in the plant that treats urban and hospital wastewaters. Amoxicillin, atenolol and diclofenac were more concentrated in winter than in summer, while ketoprofen, doxycycline and 17-β-estradiol are higher in summer. These results are probably due to the different consumption of each drug during the year, depending on their therapeutic usage. Measured drugs can be divided into three categories: those ones that are generally well removed inside the WWTP (such as acetaminophen, ketoprofen and atenolol), the partly removed ones (doxycycline, clarithromycin and 17-β-estradiol) and the refractory ones to biodegradation during activated sludge process (carbamazepine, diclofenac and amoxicillin). Regarding ecotoxicological assays, the most sensitive organisms were V. fisheri and R. subcapitata, whereas D. magna almost never reacted to the wastewaters. Seasonal variability was not clearly observed among plants and collecting time. The toxicity score evaluated all the results coming from the bioassays battery, indicating that WWTPs treatments always determined a toxicity reduction, even though a residual toxicity was still measured. This observation, together with chemical data, clearly indicate WWTPs as an important source of pharmaceuticals in the Arno river with an important environmental toxicity; therefore, the reduction of pharmaceutical load originated from point source such us WWTPs would ask in the future the adoption of refinery steps in WWTPs able to increase RE of drugs.