Potential Removal and Release of Nanomaterials from Wastewater Treatment Plants Mehlika A. Kiser 1* , Paul Westerhoff 1 , Troy M. Benn 1 , Yifei Wang 1 , Hodon Ryu 2 , Kiril Hristovski 1* 1 Arizona State University (ASU), P.O. Box 875306, Tempe, AZ 85287-5306 2 USEPA-NRMRL (MS-387), 26 W. Martin Luther King Dr., Cincinnati, OH 45268-0001 *To whom correspondence should be addressed. Email: ayla@asu.edu. ABSTRACT We studied the occurrence, characterization, and removal of nano- and larger-sized titanium (Ti) in a full-scale wastewater treatment plant. Raw sewage contained 100 – 3,000 μg/L Ti, while tertiary effluent Ti concentrations ranged from about 10 to 100 μg/L. The Ti that was removed across the treatment train accumulated in plant solids. Finished plant biosolids, tertiary effluent, and commercial toothpaste were analyzed by scanning electron microscopy, and various forms of Ti solids were observed, including aggregates containing nanoscale primary particles of titanium oxides. To support field work, laboratory batch sorption experiments were conducted with various types of nanoparticles as sorbates and wastewater biomass as sorbent. Upon exposure to 400 mg/L total suspended solids of wastewater biomass, 97% of silver nanoparticles 88% of fullerenes, 39% of functionalized nanosilver, 23% of nanoscale titanium dioxide, and only 13% of fullerol nanoparticles were removed. KEYWORDS: Nanomaterials, release, wastewater, sorption, fate and transport INTRODUCTION As the number of consumer products containing engineered nanomaterials increases, the release of nanomaterials into sewage will inevitably increase as well (Benn and Westerhoff, 2008; Kiser et al., 2009). Wastewater treatment plants (WWTPs) collect society’s wastes, including engineered nanomaterials, and distribute them into the environment through treated effluent, biosolids, and/or aerosols. Thus, quantification and characterization of the release of engineered nanomaterials from WWTPs will be an important contribution to understanding nanomaterial environmental fate and assessing exposure. Recent nanomaterial exposure modeling predicts that nanoscale titanium dioxide (TiO 2 ) is found in WWTP effluent at concentrations several times higher (0.7 – 16 μg/L) than the no-effect concentration (1 μg/L) (Nowack and Bucheli, 2007). Furthermore, TiO 2 has been used in consumer products for decades – mostly in bulk form, though increasingly in nanoscale form. Titanium (Ti) may thus serve as an indicator of the fate of nanomaterials passing through a WWTP. We report current Ti concentrations in a full- scale municipal WWTP and characterize nanoscale Ti in biosolids and tertiary effluent. To support field work, degrees of sorption of nanoscale TiO 2 , non-functionalized and functionalized nanosilver (Ag), and non-functionalized and functionalized fullerenes (C 60 ) to wastewater WEFTEC 2010 Copyright ©2010 Water Environment Federation. All Rights Reserved. 899