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Home > Nanotechnology Columns > Bergeson & Campbell, P.C. > Scientists Investigate Metallic Silver Nanoparticles in Pilot Wastewater Treatment Plant

Lynn L. Bergeson
Managing Director
Bergeson & Campbell, P.C.

Abstract:
The potential presence of silver nanoparticles (Ag-NP) in municipal wastewater has been the subject of considerable debate in recent years. While silver ion toxicity is well understood, less is understood about the environmental impacts of nanosilver, particularly on sewage treatment plants.

April 22nd, 2011

Scientists Investigate Metallic Silver Nanoparticles in Pilot Wastewater Treatment Plant

The potential presence of silver nanoparticles (Ag-NP) in municipal wastewater has been the subject of considerable debate in recent years. While silver ion toxicity is well understood, less is understood about the environmental impacts of nanosilver, particularly on sewage treatment plants.

Environmental Science & Technology posted on April 5, 2011, an article entitled "Behavior of Metallic Silver Nanoparticles in a Pilot Wastewater Treatment Plant" -- http://pubs.acs.org/doi/abs/10.1021/es1041892 The study addressed the fate of nanosilver in a waste treatment plant. Researchers from the Swiss Federal Institute of Aquatic Science and Technology and the Swiss Federal Laboratories for Material Science and Technology investigated the behavior of metallic Ag-NP in a pilot wastewater treatment plant fed with municipal wastewater.

Transmission electron microscopy (TEM) analyses confirmed that nanoscale silver particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale silver particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most silver in the sludge and in the effluent was present as Ag2S (silver sulfide -- stable, benign, inert).

Results from batch experiments suggested that Ag-NP transformation to Ag2S occurred in the non-aerated tank within less than two hours. Importantly, the researchers have concluded that the physical and chemical transformations of Ag-NP in wastewater treatment plants control the fate, transport, toxicity, and bioavailability of Ag-NP and, thus, must be considered in future risk assessments.

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