Polyvinyl chloride microplastics changed risks of antibiotic resistance genes propagation by enhancing the removal of triclosan in partial denitrification systems with different carbon source

Abstract Both Triclosan (TCS) and polyvinyl chloride microplastics (PVC MPs) were applied in personal care products, which can simultaneously enter into wastewater. However, the effects of PVC MPs on TCS removal and antibiotic resistance genes (ARGs) propagation in partial denitrification (PD) systems were unknown. In this study, the impacts of PVC MPs on PD performance, TCS removal, microbial community and ARGs in different carbon source PD systems of treating wastewater containing TCS were investigated. TCS could inhibit denitrification, but R1-acetate had stronger resistant to TCS than R2-methanol. The addition of PVC MPs could promote denitrification process of the transformation of NO2--N to N2 in R1-acetate and R2-methanol. Moreover, PVC MPs could benefit TCS degradation. The main TCS removal pathway was degradation in R1-acetate while it was adsorption in R2-methanol. PVC MPs could decrease the propagation of ARGs in R1-acetate, but increase the proliferation of ARGs in R2-methanol. Both intI1 or intI3 might be mainly responsible for ARGs propagation through horizontal gene transfer. Moreover, the potential hosts of ARGs were Candidatus Competibacter and Defluviicoccus in R1-acetate, while it was Dermatophilus in R2-methanol. This study contributes to comprehend the impacts of PVC MPs on PD systems of treating wastewater containing TCS.