Occurrence of antibiotics in hospital wastewater effluents discharged into the Niger River in Bamako, Mali. Risk assessment and solutions

Hospital wastewater effluents are a significant source of antibiotics (ABs) contamination in aquatic environments, contributing to antimicrobial resistance (AMR). This study examines 30 pharmaceutical compounds, including 22 ABs, in wastewater effluents from four hospitals in Bamako, Mali, at exit points (P_o) and discharge sites (P_f) into the Niger River. The ABs belong to nine classes, mainly fluoroquinolones, macrolides, and sulfonamides. While half of the ABs were undetected, concentrations of detected ABs ranged from 0.1 to nearly 40 μg/L. Acetyl-sulfamethoxazole (ASMX) and ciprofloxacin (CIP) recorded the highest concentrations at 38.9 ± 25.7 μg/L and 32.0 ± 4.3 μg/L, respectively. Low concentrations (<1 μg/L) were observed for azithromycin, clarithromycin, and sulfadiazine. Significant variations in concentrations between P_o and P_f were noted, with some ABs, like ASMX, achieving 100% abatement due to natural attenuation, while others, such as CIP and lincomycin, showed increases of up to 102% and 400%, respectively, possibly due to downstream accumulation or degradation of conjugates. Ecotoxicological and the potential microbial risk selection values revealed high risks (RQ > 1) at all sites although three of the hospitals reduced risks by over 50% for most of them. These findings underscore the need for effective wastewater treatment systems to mitigate ABs contamination. The study also provides critical baseline data and advocates for cost-effective, nature-based solutions like constructed wetlands and regulatory measures to reduce antibiotic pollution and curb risks for AMR proliferation in the Niger River.