Antibiotics in hospital effluent and domestic wastewater treatment plants in Doha, Qatar

Wastewater samples were collected from the main hospital's effluent (HWW), influents and effluents of the old wastewater treatment plant (OWWTP) built in 1990 and the new one (NWWTP) built in 2010 located in Doha, Qatar. Analytical methods were optimized to determine the concentrations of eight selected antibiotics (ABs): penicillin, amoxicillin, gentamicin, ciprofloxacin, tetracycline, erythromycin, metronidazole, and clavulanic acid. Samples were prepared through automated solid phase extraction (SPE) before analysis using liquid chromatography - mass spectrometry (LC–MS) with positive ion electrospray. Among the eight target compounds tested, recoveries were obtained in the range of 47.5–98%. The highest concentration of metronidazole and ciprofloxacin were detected in the HWW at levels of 5.46 μg/L and 1.99 μg/L, respectively. In effluents samples collected from both WWTPs, clavulanic acid was the most prominent compound at concentration of 84.74 μg/L. The highest concentration of erythromycin (7.20 μg/L) was detected in the influent sample collected from OWWTP. Amoxicillin, penicillin, and erythromycin were below the detection limit (0.1 μg/L). There was a significant statistical correlation between the concentrations of most of the studied antibiotics. Ciprofloxacin was highly correlated with erythromycin, clavulanic acid, and metronidazole in all influent samples, whereas the concentration of erythromycin was highly correlated with those of amoxicillin, ciprofloxacin, tetracycline and penicillin in all effluent samples. No significant difference (P ≥ 0.05) was found between concentrations of the targeted antibiotics in the NWWTP and OWWTP. Generally, both treatment plants showed effective removal rates (99.44%) of penicillin and metronidazole. However, clavulanic acid and ciprofloxacin were not removed from the effluent of either plant, even though the effluent passed through the ultrafiltration stage in the new WWTP. The findings reveal that HWW is not the only source of ABs in wastewater but direct disposal onto the sewer system could be the major source. The study calls for further investigation of additional pharmaceuticals and other emerging contaminants in the wastewater of Qatar as well as their metabolites and biodegradation products as well as application of advanced treatment technologies for highest removal rate and safe water reuse options.