**Environmental Risk and Risk of Resistance Selection Due to Antimicrobials' Occurrence in Two Polish Wastewater Treatment Plants and Receiving Surface Water**

#### **Joanna Giebułtowicz 1, Grzegorz Nał ˛ecz-Jawecki 2, Monika Harnisz 3, Dawid Kucharski 1, Ewa Korzeniewska 3 and Gra ˙zyna Płaza 4,\***


Academic Editors: Jolanta Kumirska and Teresa A. P. Rocha-Santos Received: 21 February 2020; Accepted: 21 March 2020; Published: 24 March 2020

**Abstract:** In this study, a screening of 26 selected antimicrobials using liquid chromatography coupled to a tandem mass spectrometry method in two Polish wastewater treatment plants and their receiving surface waters was provided. The highest average concentrations of metronidazole (7400 ng/L), ciprofloxacin (4300 ng/L), vancomycin (3200 ng/L), and sulfamethoxazole (3000 ng/L) were observed in influent of WWTP2. Ciprofloxacin and sulfamethoxazole were the most dominant antimicrobials in influent and e ffluent of both WWTPs. In the sludge samples the highest mean concentrations were found for ciprofloxacin (up to 28 μg/g) and norfloxacin (up to 5.3 μg/g). The removal e fficiency of tested antimicrobials was found to be more than 50% for both WWTPs. However, the presence of antimicrobials influenced their concentrations in the receiving waters. The highest antimicrobial resistance risk was estimated in influent of WWTPs for azithromycin, ciprofloxacin, clarithromycin, metronidazole, and trimethoprim and in the sludge samples for the following antimicrobials: azithromycin, ciprofloxacin, clarithromycin, norfloxacin, trimethoprim, ofloxacin, and tetracycline. The high environmental risk for exposure to azithromycin, clarithromycin, and sulfamethoxazole to both cyanobacteria and eukaryotic species in e ffluents and/or receiving water was noted. Following the obtained results, we sugges<sup>t</sup> extending the watch list of the Water Framework Directive for Union-wide monitoring with sulfamethoxazole.

**Keywords:** antibiotics; wastewater; sewage sludge; risk assessment; removal e fficiency; LC-MS/MS analysis
