## 4 Discussion
### Concentrations of Pharmaceuticals in Influents and Effluents Wastewater
Finally, a clindamycin concentration nearly three times higher than the mean across the studies was reported in a treatment facility in Warsaw (Poland) [13]. When looking at the highest PRs concentrations in the effluents of the 88 WWTPs (Table 5), sulfamethoxazole, ofloxacin and erythromycin were detected in more than 61% of studies (eleven) as the substances with the highest concentrations among the other antimicrobial substances. In studies in which sulfamethoxazole represented the most abundant PH, authors reported values ranging from 275 to 21,400 ng/L [13; 37; 49], all detected in municipal WW samples. [PERSON] and colleagues observed an ofloxacin concentration of 3051 ng/L in effluents from a WWTP in Ljubljana (Slovenia) [11]. Similarly, [PERSON] et al. reported an amount of ofloxacin equal to 648 ng/L in municipal WW effluents in Tunis (Tunisia) [36]. Moreover, erythromycin presented concentrations between 40 and 1187 ng/L in studies in which this compound was found in the highest concentrations; all were observed in municipal WW [35; 36; 50]. Although reported in thirteen studies out of the eighteen, trimethoprim was the compound found in the lowest concentrations in four of these (0.01-100 ng/L) [11; 15; 36; 37]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multirow{2}{*}{**Class**} & \multirow{2}{*}{**Pharmaceutical**} & **No. of Studies in Which the PR Was Detected (\% of the Total)** & **Max. Average Conc. (ng/L) Detected in Effluents** & **Min. Average Conc. (ng/L) Detected in Effluents * & **Mean across Studies (ng/L)** \\ \hline Amphericols & Chloramphenicol & 3 (16.7) & 97 [12] & 5.9 [50] & 50 \\ \hline Azoles & Fluconazole & 3 (16.7) & 170 [5] & 3 [35], H & 73 \\  & Metronidazole & 10 (55.6) & 3000 [11], H & 1.2 [39] & 330 \\  & Tinidazole & 1 (5.6) & 12 [49] & 9.1 [49] & 10 \\ \hline Cephalosporins & Cefalexin & 2 (11.1) & 308 [10] & 5.0 [35] & 117 \\  & Ceftazidime & 1 (5.6) & 1600 [11], H & 1600 [11], H & 1600 \\ \hline Dehydroopeptidase Inhibitors & Silastatin & 1 (5.6) & 4100 [11] & 4100 [11], H & 4100 \\ \hline Diphenylethers & Triclosan & 1 (5.6) & 7.4 [12] & 0.9 [12] & 4.2 \\ \hline Folic Acid Inhibitors & Trimethoprim & 14 (77.8) & 26,100 [6] & 1.6 [17] & 1979 \\ \hline Glycopeptide antibiotics & Vancomycin & 2 (11.1) & 162 [13] & 81 [14] & 119 \\ \hline Lincosamides & Clindamycin & 5 (27.8) & 290 [13] & 0.5 [39] & 71 \\  & Lincomycin & 4 (22.2) & 56 [13] & 1.5 [12] & 26 \\ \hline Macrolides & Azithromycin & 8 (44.4) & 56,666 [17] & 0.1 [39] & 4387 \\  & Clarithromycin & 12 (66.7) & 15,000 [11], H & 0.2 [39] & 750 \\  & Erythromycin & 11 (61.1) & 1187 [36] & 0.1 [39] & 304 \\  & Roxithromycin & 6 (33.3) & 6272 [17] & 3.6 [17] & 882 \\ \hline Penicillins & Ampicillin & 4 (22.2) & 790 [16], H & 60 [16] & 254 \\ \hline Penicillins-Like & Amoxicillin & 4 (22.2) & 1600 [15] & 40 [12] & 463 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: List of 45 pharmaceuticals detected in 88 WWTPs, investigated in the eighteen studies. Maximum and minimum average concentrations and means were reported and expressed in ng/L. The high and ubiquitous presence of these compounds in influents and effluents depends on several factors, mainly related to the consumption and the physicochemical characteristics of the drug. For instance, combinations of trimethoprim and sulfamethoxazole are widely used to treat urinary and respiratory tract infections and are also administered to patients with AIDS or other conditions of immunosuppression [15]. Furthermore, the constant presence of PRs in WW effluents can be attributed to the process of sorption that may occur when PRs accumulate in the sludge of WWTPs. Especially during the final phases of treatment, the substances attached to the sediment particles might be redissolved due to gas bubbling [39], leading to an increase in the detected PR concentration [13].