Bacterial community change and antibiotic resistance promotion after exposure to sulfadiazine and the role of UV/H2O2-GAC treatment

Abstract

Effects of sulfadiazine on bacterial community and antibiotic resistance genes (ARGs) in drinking water distribution systems (DWDSs) were investigated in this study. Three DWDSs, including sand filtered (SF) DWDSs, granular active carbon (GAC) filtration DWDSs, and UV/H2O2-GAC DWDSs, were used to deliver sand filtered water, GAC filtered water, and UV/H2O2-GAC treated water, respectively. UV/H2O2-GAC filtration can remove the dissolved organic matter effectively, which resulted in the lowest bacterial diversity, biomass and ARGs in effluents and biofilm of DWDSs. When sulfadiazine was added to the sand filtered water, the dehydrogenase concentration and bacterial activity of bacterial community increased in effluents and biofilm of different DWDSs, inducing more extracellular polymeric substances (EPS) production. The proteins increasement percentage was 26.9%, 11.7% and 19.1% in biofilm of three DWDSs, respectively. And the proteins increased to 830.30 ± 20.56 μg cm−2, 687.04 ± 18.65 μg cm−2 and 586.07 ± 16.24 μg cm−2, respectively. The increase of EPS promoted biofilm formation and increased the chlorine-resistance capability of bacteria. Therefore, the relative abundance of Clostridium_sensu_stricto_1 increased to 12.22%, 10.41% and 0.33% in biofilm of the three DWDSs, respectively. Candidatus_Odyssella also increased in the effluents and biofilm of the three DWDSs. These antibiotic resistance bacteria increase in DWDSs also induced the ARGs promotion, including sul1, sul2, sul3, mexA and class 1 integrons (int1). However, UV/H2O2-GAC filtration induced the lowest increase of dehydrogenase and EPS production through sulfadiazine removal efficiently, resulting in the least bacterial community change and ARGs promotion in UV/H2O2-GAC DWDSs.