Engineered nanoparticles are increasingly incorporated into consumer products and inevitably released into wastewater. This study explored the interaction between wastewater biofilm and frequently used silver nanoparticles (Ag-NPs). Biofilm was grown in a non-limiting synthetic wastewater (SW) in two types of reactors: a CDC biofilm reactor (CBR) and a flow cell. Three typical wastewater bacteria (Acinetobacter calcoaceticus, Comamonas testosteroni, and Delftia acidovorans) were used as a model consortium, and biofilm functionality, structure, and viability were monitored with and without Ag-NPs exposure in CBR. Upon initial contact with SW, less than 1% of silver remained Ag-NPs, while the the majority (&gt;97%) formed agglomerates larger than 100 nm. No significant change in biofilm viability and ability to remove nutrients was observed at 50 ppb of Ag-NPs. However, significant cell stress was detected with the generation of excess reactive oxygen species. To measure Ag-NP accumulation within biofilm, flow cell experiments were perfomed for each species singly, in dual combinations, and mixed under the Ag-NP exposure at 200 ppb. The single species biofilm accumulated the least amount of silver, approximately 0.01 ng mm-2. The dual species, A. calcoaceticus and D. acidovorans accumulated 0.43 ng mm-2, the highest measured concentration of these combinations. This combination was then further tested for the possible release of silver. After Ag-NP exposure, biofilm detachment and total silver concentrations in influent and effluent were measured. While effluent cell counts did not significantly change (p&gt;0.05), the measured silver attached to the biofilm significantly decreased (p=0.04). This shows that small concentrations of silver attached to the biofilm, and were subsequently released. Given the dynamic nature of living biofilm, this study indicates that wastewater biofilm plays a small role in silver transport in wastewater networks. Further, this work could potentially apply to the fundamental understanding of biofilm – NP interactions in other systems.

Interaction between silver nanoparticles and model wastewater biofilm

256th National Meeting (2018)

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