Shifts in Nitrogen Removal Performance and Microbial Communities in Constructed Wetlands After Short-term Exposure to Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO 2 NPs) can potentially impact constructed wetlands (CWs). The aim of this study was to investigate the rapid impacts on nitrogen removal performance and on the microbial community after short-term exposure to TiO 2 NPs in CWs, which were determined via 16S rDNA amplicon sequencing and Biolog-Eco technologies. The results showed that removal efficiencies declined by 23.9%, 32.2%, and 38.8% for ammonia nitrogen (NH 4 + -N) and by 26.5%, 43.4%, and 71.4% for nitrate nitrogen at TiO 2 NP concentrations of 50, 100, and 150 mg/L, respectively. Bacterial damage and TiO 2 NP agglomeration on the packing increased as the TiO 2 NP concentration increased. Microbes showed different tolerances against TiO 2 NPs, and members, such as the bacteria removing organic pollutants and NH 4 + -N, were susceptible to TiO 2 NPs. The order of microbial utilisation of the six carbon sources was determined, and the utilisation ratios declined as TiO 2 NP concentration increased. The concentration of 50 mg/L TiO 2 NPs impaired the functions of nitrifiers and denitrifiers in CWs after short-term exposure, and higher concentrations (100 mg/L and 200 mg/L) had no additional negative impact on the packing compared with the concentration of 50 mg/L.