Ozone pretreatment of wastewater containing aromatics reduces antibiotic resistance genes in bioreactors: The example of p-aminophenol.

Aromatic matters are widely present in wastewater, especially industrial wastewater, and may lead to a high abundance of antibiotic resistance genes (ARGs) in wastewater treatment bioreactors and stimulate horizontal transfers of ARGs. Here, we investigated a practical approach that applying ozone pretreatment to mitigate ARGs in bioreactors treating wastewater containing a typical aromatic pollutant, p-aminophenol (PAP). The results showed that ozone pretreatment could effectively reduce the aromaticity of wastewater, and the relative abundance of ARGs in the bioreactor fed with ozone treated wastewater decreased by over 70% compared to the control reactor. Multidrug, quinolone, mupirocin, polymyxin, aminoglycoside, glycopeptide, beta-lactam, and trimethoprim resistance genes were all reduced in the bioreactors receiving wastewater pretreated by ozone. Metagenomic analysis suggested that the reduction of ARGs could be attributed to the co-occurrence of ARGs and aromatic degradation genes in bacteria. Furthermore, we expanded our analysis to investigate 71 metagenomes from different environments, and the results indicated that the impact of aromatics on ARG abundance widely occurs in various ecosystems and confirmed that high levels of aromatics could lead to high abundance of ARGs. Taken together, our work confirmed that the aromatics played critical roles in selecting ARGs and proposed a feasible approach to reduce ARGs in wastewater treatment bioreactors.