title: Fate of zinc oxide and silver nanoparticles in a pilot wastewater treatment plant and in processed biosolids.
abstract: Chemical transformations of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) during wastewater treatment and sludge treatment must be characterized to accurately assess the risks that these nanomaterials pose from land application of biosolids. Here, X-ray absorption spectroscopy (XAS) and supporting characterization methods are used to determine the chemical speciation of Ag and Zn in sludge from a pilot wastewater treatment plant (WWTP) that had received PVP coated 50 nm Ag NPs and 30 nm ZnO NPs, dissolved metal ions, or no added metal. The effects of composting and lime and heat treatment on metal speciation in the resulting biosolids were also examined. All added Ag was converted to Ag2S, regardless of the form of Ag added (NP vs ionic). Zn was transformed to three Zn-containing species, ZnS, Zn3(PO4)2, and Zn associated Fe oxy/hydroxides, also regardless of the form of Zn added. Zn speciation was the same in the unamended control sludge. Ag2S persisted in all sludge treatments. Zn3(PO4)2 persisted in sludge and biosolids, but the ratio of ZnS and Zn associated with Fe oxy/hydroxide depended on the redox state and water content of the biosolids. Limited differences in Zn and Ag speciation among NP-dosed, ion-dosed, and control biosolids indicate that these nanoparticles are transformed to similar chemical forms as bulk metals already entering the WWTP.
authors.affiliation: Department of Civil & Environmental Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Rui
authors.initials: R
authors.lastname: Ma
authors.forename: Clément
authors.initials: C
authors.lastname: Levard
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Judy
authors.forename: Jason M
authors.initials: JM
authors.lastname: Unrine
authors.forename: Mark
authors.initials: M
authors.lastname: Durenkamp
authors.forename: Ben
authors.initials: B
authors.lastname: Martin
authors.forename: Bruce
authors.initials: B
authors.lastname: Jefferson
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Lowry
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry; D006358:Hot Temperature; D053768:Metal Nanoparticles / Q000032:analysis* / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D012834:Silver / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D015034:Zinc Oxide / Q000032:analysis* / Q000737:chemistry
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D012834:Silver; D012987:Soil; D062065:Wastewater; D014874:Water Pollutants, Chemical; D015034:Zinc Oxide; C016538:lime