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

Titanium dioxide nanoparticles (TiO2 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 TiO2 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 (NH4+-N) and by 26.5%, 43.4%, and 71.4% for nitrate nitrogen at TiO2 NP concentrations of 50, 100, and 150 mg/L, respectively. Bacterial damage and TiO2 NP agglomeration on the packing increased as the TiO2 NP concentration increased. Microbes showed different tolerances against TiO2 NPs, and members, such as the bacteria removing organic pollutants and NH4+-N, were susceptible to TiO2 NPs. The order of microbial utilisation of the six carbon sources was determined, and the utilisation ratios declined as TiO2 NP concentration increased. The concentration of 50 mg/L TiO2 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.

Automated summary

The study found that TiO2 NPs have significant impacts on nitrogen removal performance and microbial communities in constructed wetlands. As the concentration of TiO2 NPs increases, nitrogen removal efficiency decreases and causes damage to the microbes.