Transformation of silver nanoparticles in fresh, aged, and incinerated biosolids Christopher A. Impellitteri a, *, Stephen Harmon a , R. Gune Silva b , Bradley W. Miller c , Kirk G. Scheckel a , Todd P. Luxton a , Donald Schupp b , Srinivas Panguluri b a United States Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA b Shaw Environmental Inc., 1600 Gest Street, U.S. EPA Test and Evaluation Facility, Cincinnati, OH 45204, USA c Oak Ridge Institute for Science and Education, P.O. Box 117, Oak Ridge, TN 37831, USA article info Article history: Received 25 May 2012 Received in revised form 1 October 2012 Accepted 3 December 2012 Available online 21 March 2013 Keywords: Silver Nanoparticles Biosolids Incineration Wastewater treatment abstract The purpose of this research was to assess the chemical transformation of silver nano- particles (AgNPs) in aged, fresh, and incinerated biosolids in order to provide information for AgNP life cycle analyses. Silver nanoparticles were introduced to the influent of a pilot- scale wastewater (WW) treatment system consisting of a primary clarifier (PC), aeration basin, and secondary clarifier. The partitioning of the AgNPs between the aqueous and solid phases in the system was monitored. Less than 3% of the total AgNPs introduced into the PC were measured at the overflow of the PC. Biosolids were collected from the pilot- scale system for silver analyses, including Ag concentration and speciation. Additionally, biosolids were collected from a publically owned treatment works (POTW). The POTW biosolids were spiked with AgNPs, AgNO 3 , and Ag 2 S. One set of the spiked POTW biosolids was aged for one month, and another set was analyzed within 24 h via X-ray absorption spectroscopy (XAS) and scanning electron microscopy/energy dispersive X-ray spectros- copy (SEM-EDX) in order to determine Ag chemical speciation and elemental associations. Replicates of the aged and 24-h samples were also incinerated at 850  C for 4 h. The re- sidual ash was analyzed by XAS and SEM-EDX. The results show that AgNPs are converted to Ag-sulfur (as sulfide and sulfhydryl) species in fresh and aged biosolids, which is in agreement with other studies on AgNPs in biosolids. Results from linear combination fitting of the XAS data for incinerated biosolids show that a significant proportion of the spiked silver (30e50%) is converted to elemental Ag in the incineration process. In addition to elemental Ag, the results suggest the presence of additional AgeS complexes such as Ag 2 SO 4 (up to 25%), and silver associated with sulfhydryl groups (26e50%) in the inciner- ated biosolids. Incinerated biosolids spiked with AgNO 3 and Ag 2 S exhibited similar trans- formations. These transformations of AgNPs should be accounted for in life-cycle analyses of AgNPs and in management decisions regarding the disposal of incinerated biosolids. Published by Elsevier Ltd. * Corresponding author. Tel.: þ1 513 487 2872; fax: þ1 513 569 7658. E-mail address: impellitteri.christopher@epa.gov (C.A. Impellitteri). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 47 (2013) 3878 e3886 0043-1354/$ e see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.watres.2012.12.041