Micro-Nano Aeration Enhanced Ofloxacin Removal and Inhibited Antibiotic Resistance Gene Spread During the Aerobic Biofilm Treatment of Rural Domestic Sewage

Abstract

Micro-nano aeration (MNA) has great potential for emerging contaminant removal. However, little is known about how MNA affects the fate of antibiotics and antibiotic resistance genes (ARGs) during rural domestic sewage treatment. Here, MNA was applied to replace conventional aeration (CVA) in aerobic biofilm systems and observe ofloxacin (OFL) removal and ARG spread. MNA increased OFL removal by 17.27%-40.54% and decreased total ARG abundance by 36.37%-54.98%, compared to CVA. MNA-induced biofilm rough morphology, high zeta potential, and less extracellular polymeric substances (EPS) secretion can adsorb more OFL+. High dissolved oxygen and temperature caused by MNA could enrich aerobic bacteria and their carrying OFL degrading genes, which enhanced OFL biodegradation. MNA inhibited the enrichment of ARG host bacteria, and more importantly, these ARG hosts were observed to acquire ARGs possibly via horizontal gene transfer (HGT). The functional profile involved in the HGT process, including reactive oxygen species production, membrane permeability, mobile genetic elements (MGEs), adenosine triphosphate synthesis, and EPS content were also mitigated by MNA, inhibiting ARG spread. Partial least-squares path model indicated that MGEs might be the primary factor in inhibiting ARG spread. We provide insight into how MNA enhanced antibiotic removal and inhibited ARG spread in aerobic biofilm systems.

Keywords: micro-nano aeration, aerobic biofilm, Antibiotic resistance genes, Horizontal gene transfer, ofloxacin