The removal of antibiotic, antibiotic resistant bacteria and genes in persulfate oxidation system via activating by antibiotic fermentation dregs derived biochar

Abstract

To reduce the adverse effects of antibiotics and antibiotic resistance genes (ARGs) in the environment, nitrogen-doped biochar (NLBH), derived from lincomycin fermentation dregs (LFD), was employed as an activator in a persulfate (PDS) oxidation system. The system was evaluated for its ability to degrade tetracycline (TC), inactivate antibiotic resistant bacteria (ARB) and remove ARGs. The degradation efficiency of TC in the NLBH/PDS system (70.1%) was higher than that in the pristine biochar/PDS system (10.3%). It was confirmed that the defects and edge pyridinic nitrogen generated in the nitrogen doping process were the reactive sites for PDS activation. According to electron paramagnetic resonance (EPR) and radical quenching experiments, the major mechanism for PDS activation was a non-radical pathway dominated by singlet oxygen (1O2). Radical pathways involving sulfate (SO4·-) and hydroxyl radicals (·OH) were also at play in the NLBH/PDS system, but their role was minor. TC was principally degraded by hydroxylation, demethylation, and decarboxylation, and within 90 min, the NLBH/PDS system effectively inactivated 71.5% of ARB (Pseudomonas sp. HLS-6). Intracellular ARGs (iARGs; sul1, sul2) and intI1 had log reduction efficiencies of 2.73–4.04 and 2.70, respectively, whereas, extracellular ARGs (sul1 and sul2) and intI1 accumulated noticeably by 1.52–4.18-and 4.92-log, respectively. This work highlights a promising alternative technique for the removal of antibiotics, ARB and iARGs in future advanced wastewater treatment systems.