Seasonal occurrence, removal efficiency and associated ecological risk assessment of three antibiotics in a municipal wastewater treatment plant in Egypt

Abstract

Residual concentrations of antibiotics have been detected in municipal wastewater treatment plants (WWTPs) in many countries around the world at the levels of microgram and nano-gram per liter. To the best of our knowledge, based on reviewing related literature, no studies have been conducted so far focusing on evaluating the residual concentration of antibiotics in WWTPs in Egypt. Thirty-six wastewater samples were collected from the influent and the effluent of Tezmant WWTP in Beni-Suef governorate, Egypt during summer and winter seasons. Three antibiotics were selected based on the consumption rate. The selected antibiotics were investigated in terms of their occurrence, removal efficiency and ecological risk assessment. Solid phase extraction was adopted for the sample pre-concentration then the analysis process was carried out using liquid chromatography tandem mass spectrometry (LC–MS/MS). For the influent samples, the highest detected concentrations (μg/L) are 0.98, 0.66 and 0.48 for sulfamethoxazole (SMZ), azithromycin (AZM) and ciprofloxacin (CIP) respectively. Regarding the effluent samples, the highest level is recorded for SMZ (1.72 μg/L), followed by CIP (0.31 μg/L) and finally AZM (0.25 μg/L). The removal efficiency for the investigated antibiotics from the WWTP ranges from 17.6% to 78.8% in winter and from -30.6% to 80.9% in summer. Ecological risk assessment revealed that SMZ shows high acute toxicity for plant and algae; whereas, CIP for plant and bacterium. Anti- resistance bacteria for the three antibiotics will appear based on Risk Quotient (RQ) calculated.