System of multi-layered environmental media for the removal of antibiotics from wastewater

In relation to the dissemination of antibiotic resistance in the environment, strategies to remove antibiotics from wastewater are urgently required. As such, we designed and tested a system of layered environmental media (consisting of gravel, sand, soil, and soil + biochar) through which antibiotic-laden water was pumped. The removal efficiency of the system was assessed. Overall removal efficiencies of the antibiotics amoxicillin, cefalexin, sulfadiazine, and tetracycline were 81, 91, 51, and 98 %, respectively. Amoxicillin and cefalexin removal was largely controlled by chemical degradation within the gravel layer, whereas sulfadiazine was largely re-moved via both chemical and microbial degradation in the soil + biochar layer and tetracycline was lost via hydrolysis reactions in the gravel layer. The results indicate the importance of using layers of different media to target different compounds. Increasing the hydraulic retention time of the system improved removal efficiency, especially for amoxicillin and cefalexin, which had half-lives that were shorter than the hydraulic retention time. The presence of dissolved organic matter in the influent water generally reduced antibiotic removal efficiency. Overall, the results indicate the potential of the system for antibiotic removal from water and highlight ways in which improvements to removal efficacy may be achieved.