Sharon Walker received her Ph.D. in Environmental Engineering, from the Department of Chemical Engineering at Yale University in 2004. She earned her M.S. in Chemical and Environmental Engineering from Yale in 2000 and two Bachelor of Science degrees from the University of Southern California in Environmental Engineering and Environmental Studies in 1998. Dr. Walker is a member of the American Chemical Society (ACS), Association for Environmental Engineering and Science Professors (AEESP), American Institute of Chemical Engineers (AIChE), Association of Women in Science (AWIS), and Society of Women Engineers (SWE). She is also a member of Chi Epsilon, Tau Beta Pi, and Golden Key honor societies. She is currently a faculty advisor to the UC Riverside Alpha Beta chapter of Tau Beta Pi and the Society of Women Engineers UCR chapter. She was awarded the 2008 Woman of Distinction Award by the Girl Scouts of San Gorgonio Council for her outreach efforts in Science Technology, Engineering, and Math (STEM) education and the 2011 Chancellor's Award for mentoring undergraduates in research. Other honors include her Fulbright Scholarship at Ben Gurion University in Israel (2009-2010) and an ELATE fellowship (2014-2015). Most recently, Dr. Walker served as the Associate Dean of the Graduate Division at UCR (2014-2015).



Travis Waller and Sharon L. Walker
Dept. of Chemical and Environmental Engineering, University of California, Riverside

Titanium dioxide (TiO2) used in food and consumer products accounts for a large fraction of nanoparticles released to wastewater treatment facilities. Septic tanks are decentralized wastewater treatment systems in approximately 20% of American households and are well known for maintenance issues, as well as, system failure. Optimum septic system function relies on microbial degradation of wastewater compounds before release into groundwater. TiO2 incorporated in consumer based and food products has a direct pathway to WWTPs (e.g. septic system) via bathing and excretion. Wastewater treatment efficiency in the less studied septic systems is of concern as multiple studies have reported geno- and cyto- toxicity of TiO2 to microorganisms in aqueous environments. This study considers the impacts of industrial and food grade TiO2 on the waste degradative capacity of the microbial community determined via effluent quality, in addition to, the biochemical and the phenotypic response of the microbiota. Further, the transformation of TiO2 in the complex septic system matrix was considered. Preliminary findings of industrial grade TiO2 exposures indicate water quality changes such as consumption of alkalinity and decreases of turbidity and total dissolved solids. Phenotypic characteristics of the microbial community, including cellular concentration, hydrophobicity, and electrophoretic mobility, remain largely unchanged suggesting a compositionally stable community after exposure to industrial grade TiO2. Implications of nanoparticles in wastewater treatment, as well as, experimental challenges of studying nanoparticles in complex environments will be discussed in greater detail.