Abstract: Silver nanoparticles (Ag-NPs) have been one of the most commercialized nanomaterials nowadays. Due to their strong antimicrobial properties, Ag-NPs are used extensively in a wide range of nanotechnology-enhanced consumer products. Their widespread production and utilization inevitably cause the release of Ag-NPs into wastewater collection and treatment plants. With the rapid increase in the number of Ag-NPs products in the market, there are particular concerns on the risks associated with the interactions between Ag-NPs and wastewater microorganisms, which would potentially threaten wastewater treatment functions. Although it is expected that Ag-NPs have inhibitive effects on microbial activities in wastewater treatment plants (WWTPs), their fate and transformation in wastewater remain unclear because of the complex and uncertainty of Ag-NPs in WWTPs. In this review, we summarized the antimicrobial behaviors of Ag-NPs in WWTPs and implications in the functions of microorganisms for removing organic matter, nitrogen and phosphorus. To better understand the associated risks of Ag-NPs in WWTPs, we highlight current progress and knowledge gaps. Future perspectives are also proposed, including (1) characterization of the dynamics of Ag-NPs in WWTPs, (2) assessment of the potential toxicity of Ag-NPs to functional microorganisms (e.g. removing pollutants), and (3) development of strategies to mitigate the risks of Ag-NPs in WWTPs. These discussions deliver important theoretical basis for assessing environmental risks of Ag-NPs in sewage systems.

Key words: silver nanoparticles, wastewater treatment, biotoxicity, environmental risk.