## 3 Results and Discussion
### Concentration and Removal of PhACs and Antibiotics in Assamra WWTP
Figure 2: Concentrations (ng L\({}^{-1}\)) of pharmaceutically active compounds (PhACs, excluding antibiotics) in Assamra wastewater treatment plant (WWTP) influent (\(n=2\)) and effluent (\(n=2\)), and in water from the Zarqa River at Sukhna station, (\(n=2\)), Twahin Eledwan station (\(n=2\)), Military station (\(n=2\)) and Jerash stream (\(n=2\)). S1, S2 = parallel samples. that antibiotics in the classes fluoroquinolones, macrolides, penicillin, and antiprotozoan are the most commonly dispensed antibiotics in Jordan. The combined antibiotics (\(\Sigma\)Antibiotics) concentration was 510-860 ng L\({}^{-1}\) in influent and 2300-2600 ng L\({}^{-1}\) in the effluent (Figure 4, Table S5). After passing through the treatment process, only the concentration of clarithromycin decreased (from 308 to 82 ng L\({}^{-1}\); removal rate 73% on average). [PERSON] et al. reviewed the WWTPs performances to remove the PhACs in various countries [44]. The reported studies of 12 kinds of antibiotics, including Ofloxacin and Erythromycin, all observed positive values as removal ratio. However, the present study showed 2- to 5-fold higher concentrations of all other antibiotics in effluent than the levels in influent. Ciprofloxacin, which was not detected in the influent, was found in the effluent samples. Hydrolyses of organic matter of wastewater of solid phase and hence the release of ciprofloxacin bound to solids into the liquid phase could have occurred, explaining the increase of the substance in the effluent. Moreover, antibiotics partition into water is generally based on the chemical and physical properties of the antibiotic itself [45]. For example, clarithromycin has high partition coefficients (log Kow = 3.16, Koc = 150, Table S2) and low solubility. These properties suggest that clarithromycin is likely to adsorb to the solids in wastewater, which explains this substance's reduction. In contrast, ofloxacin has low log Kow (\(-2\)) and high-water solubility (6.7 \(\times\) 105 mg L\({}^{-1}\)) (Table S2), suggesting that it is water-soluble, explaining the high concentrations in the effluent. In this study, we did not analyse the concentrations of antibiotics in the solid phase of raw wastewater or the WWTP sludge. It is likely that a fraction of the antibiotics initially partitioned to organic matter or accumulated in biomass in the wastewater was released after hydrolysis of the organic matter during biological treatment in the WWTP. This condition would partly explain the increase in antibiotic concentrations in effluent compared with influent, as also suggested in other studies [45; 46]. Another explanation could be the presence of antibiotic conjugates or metabolites, which were cleaved back to their mother forms during the treatment process [46; 47]. Figure 4: Concentrations of antibiotics (ng L\({}^{-1}\)) in Assamra wastewater treatment plant (WWTP) influent (\(n=2\)) and effluent (\(n=2\)), and in water from the Zarqa River at Sukhna station, (\(n=2\)), Twahin Eledwan station (\(n=2\)), Military station (\(n=2\)), and Jerash stream (\(n=2\)). S1, S2 = parallel samples.