Detection of antibiotics from wastewater treatment plants in Addis Ababa, Ethiopia

Abstract

Background: Antibiotics are the critical elements widely used to fight different bacterial infections. Amoxicillin, ciprofloxacin and sulfamethoxazole are relatively the most commonly prescribed antibiotics. Once consumed, most antibiotic drugs are excreted in unmetabolized forms via urines and feces and may contaminate the environment if not well treated. Thus, improperly disposed antibiotics are contributing for the development of bacterial resistances and environmental pollution. In urban areas, due to weak removal efficiency of wastewater treatment plants (WWTPs), municipal wastewater is considered as source for release of antibiotics into the environments. Therefore, investigating the concentration of antibiotics in municipal wastewater is critical to take appropriate mitigation strategies. Objective: The aim of this study was to evaluate occurrence of selected antibiotics in the municipal wastewater (influent and effluent) in Addis Ababa, Ethiopia Methods: The study was carried out from January to February, 2022 at Addis Ababa. A 1 L wastewater sample was collected from each sampling point (influent and effluent) of two WWTP using polyethylene bottles as grab samples in February, 2022, kept in the ice box and transported to the laboratory. Samples were appropriately stored until analysis. Before analysis, the PH of samples were adjusted using HCL, chelating agent (Na2EDTA) was added then, and extracted by solid phase extraction using C18 cartridges. Identification and quantification of target antibiotics were performed using HPLC-UV. The laboratory analysis was conducted in Ethiopian food and drug authority drug quality laboratory. Results: The results of this study revealed the presence of ciprofloxacin and sulfamethoxazole in influent wastewater of two treatment plants. Among investigated antibiotics, only sulfamethoxazole is detected in effluent sample of Site B. Amoxicillin is not detected in all wastewater samples of two WWTPs. The concentration (0.67 ±0.15 µg/L) of ciprofloxacin detected in influent sample of Site A treatment plant was relatively highest. The removal efficiency of WWTPs for the two detected antibiotics ranged from 36% to 100%. The removal efficiency was determined as the percentage of the concentrations difference between influents and effluents samples of each WWTP. II Highest removal percentages (100%) were recorded for both antibiotics in Site A treatment plant. The lowest removal percentage for sulfamethoxazole (36%) was recorded in Site B wastewater treatment plant. Conclusion and recommendation: from three investigated antibiotics in this study, two were detected in influent municipal wastewater of two treatment plants with the concentration ranging from < LOQ-0.67ug/L for ciprofloxacin and < LOQ-0.06 ug/L for sulfamethoxazole respectively. In one treatment plant, sulfamethoxazole was still detected in final effluent at the concentration < LOQ. The concentration of ciprofloxacin (0.67±0.15 µg/L) measured in the present study is higher than the levels of Predicted No-Effect Concentrations (PNEC) to the environment for this compound (0.45 µg/L). This study recommends the more detailed studies of levels of these antibiotics in different water environments of Addis Ababa