Impact of NH4+-N on Organic Micropollutant Removal and Antibiotic Resistance Gene Occurrence during Simulated Riverbank Filtration
Jian Zhao (Tsinghua University)
Qiaojuan Wang (Chinese Academy of Sciences)
Yangrui Huang (Tsinghua University)
Shangbiao Fang (Tsinghua University)
Gang Liu (TU Delft - Sanitary Engineering, Chinese Academy of Sciences)
Weixiao Qi (Tsinghua University)
Yaohui Bai (Chinese Academy of Sciences)
Walter van der Meer (University of Twente)
Jiuhui Qu (Tsinghua University)
Huijuan Liu (Tsinghua University)
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Abstract
Organic micropollutants (OMPs) facilitate the spread of antibiotic resistance genes (ARGs). Ammonia-oxidizing microorganisms (AOMs) are crucial for OMP degradation during riverbank filtration (RBF) and significantly influenced by NH4+-N concentrations. However, the effect of NH4+-N on OMP removal and ARG occurrence in RBF remains unclear. This study aimed to examine the effects of low (∼0.1 mg/L) and high (∼2.2 mg/L) NH4+-N concentrations on OMP removal, ARG occurrence, and microbial communities. NH4+-N addition had no significant effect on the removal of 108 out of 128 OMPs, suggesting that other factors primarily govern the removal process. Notably, NH4+-N addition enhanced the removal of 20 OMPs by 3–70%, including three quinolones (e.g., flumequine), indicating its promotion of specific OMP removals. This effect may primarily result from NH4+-N enhancing OMP biotransformation through the stimulation of AOMs (particularly AOA and comammox) and heterotrophs (e.g., Bradyrhizobium). Furthermore, NH4+-N addition significantly reduced the abundance of eight ARGs, including quinolone ARGs, likely due to its inhibition of antibiotic-resistant bacteria. Additionally, we hypothesize that NH4+-N alleviates OMP selective pressure on microorganisms by promoting OMP conversion through AOMs. This study enhances the understanding of microbe-mediated OMP removal in the presence of NH4+-N and its impact on ARG occurrence during RBF.