Simultaneous elimination of amoxicillin and antibiotic resistance genes in activated sludge process: Contributions of easy-to-biodegrade food

Antibiotics are continuously released into aquatic environments and ecosystems where they accumulate, which increases risks from the transmission of antibiotic resistance genes (ARGs). However, it is difficult to completely remove antibiotics by conventional biological methods, and during such treatment, ARGs may spread via the activated sludge process. Easy-to-biodegrade food have been reported to improve the removal of toxic pollutants, and therefore, this study investigated whether such co-substrates may also decrease the abundance of ARGs and their transferal. This study investigated amoxicillin (AMO) degradation using 0-100 mg/L acetate sodium as cosubstrate in a sequencing biological reactor. Proteobacteria, Bacteroidetes, and Actinobacteria were identified as dominant phyla for AMO removal and mineralization. Furthermore, acetate addition increased the abundances of adeF and mdsC as efflux resistance genes, which improved microbial resistance, the coping ability of AMO toxicity, and the repair of the damage from AMO. As a result, acetate addition contributed to almost 100% AMO removal and stabilized the chemical oxygen demand (similar to 20 mg/L) in effluents when the influent AMO fluctuated from 20 to 100 mg/L. Moreover, the total abundance of ARGs decreased by approximately similar to 30%, and the proportion of the most dominant antibiotic resistance bacteria Proteobacteria decreased by similar to 9%. The total abundance of plasmids that encode ARGs decreased by as much as similar to 30%, implying that the ARG spreading risks were alleviated. In summary, easy-to-biodegrade food contributed to the simultaneous elimination of antibiotics and ARGs in an activated sludge process. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study found that adding sodium acetate can enhance antibiotic degradation, reduce the abundance and transmission of ARGs, improve microbial resistance to antibiotic toxicity, and stabilize the chemical oxygen demand in wastewater discharge.