Removal of antibacterial drugs in urban wastewater treatment plants

The aim of the study was to detect and quantify selected antibacterial drugs in the raw and treated wastewater collected under various temperature conditions (i.e. winter and summer period) from two urban wastewater treatment plants (WWTPs), located in the northern and southern part of Poland. An additional goal of the study was to estimate the effectiveness of the removal of these antibacterial drugs in the above-mentioned conditions. For the study were selected: clarithromycin (CLA), erythromycin (ERY), roxithromycin (ROX), sulfamethoxazole (SMX), N-acetyl-sulfamethoxazole (N-Ac-SMX), sulfamethoxine (SMN), sulfamerazine (SMR), tiamulin (TIA), and trimethoprim (TRP). The study showed that CLA, ERY, ROX, SMX, TRP, and N-Ac-SMX (main SMX metabolite) were detected in all wastewater samples, regardless of the place of collection and the season of the sampling, while SMN, SMR, and TIA were not detected in the investigated wastewater. The studies have shown that N-Ac-SMX was the most efficiently removed compound at both treatment plants, regardless of the process temperature (over 95%), however, this substance may reversibly transform into the origin form of SMX under the conditions prevailing at WWTPs, which means that the removal can be only apparent. In the study, the temperature was an important parameter affecting the removal efficiency of CLA, ROX, and TRP. The removal efficiency of these substances always has been higher in summer than in the winter period. The process was also slightly more effective at WWTP 2. At WWTP 2, the average removal for CLA, ROX, and TRP in the summer period was equal to 76%, 47%, and 38%, respectively. Erythromycin, was a substance that was not degraded in any of the investigated technological systems and no effect of temperature on the removal efficiency was observed.