Fate of silver nanoparticles in constructed wetlands and its influence on performance and microbiome in the ecosystems after a 450-day exposure

[Display omitted] •The effects of long-term exposure to sublethal concentration AgNPs in CWs were investigated.•Performance of CWs did not decline after a 450-day exposure of AgNPs.•The soil layer of CWs acted as a major sink for nanoparticle accumulation and transformation.•Sustained AgNPs exposure affected the microbial community structure and key functional bacteria. Great controversy still exists on the ecological effects of silver nanoparticles (AgNPs) especially at relatively low concentrations. The performance, fate of AgNPs and microbiome in CWs were evaluated under a long-term exposure to AgNPs (0, 50 and 200 µg/L) for 450 days. Results showed that AgNPs (50, 200 µg/L) caused no obviously negative effects on COD removal whereas nitrogen and phosphorus removals were slightly stimulated. AgNPs could be removed efficiently from wastewater attributed to the accumulations of soil and plant tissues. Mass balance of AgNPs was analysed and soil layer of CWs was the major sink of nanoparticles. High-throughput sequencing further revealed the impact of AgNPs on the ecological structure of CWs. Moreover, the presence of AgNPs altered the relative abundances of key functional bacteria. The ecological risks of persistent exposure to low concentrations AgNPs should not be ignored, even though it did not result in deterioration of the CWs’ operating performance in our studies.