- Bourns College of Engineering
- Chemical/Environmental Engineering
Dr. Walker holds the John Babbage Chair in Environmental Engineering at the University of California, Riverside and is actively involved in several professional societies including American Chemical Society, the American Society of Microbiology, the Society of Women Engineers, and the Association of Environmental Engineering and Science Professors.
- Ph.D. Environmental Engineering 2004
- M.S. Chemical Engineering 2000
- B.S Environmental Engineering 1998
- University of Southern California
- B.S. Environmental Studies 1998
- University of Southern California
2010 - 2011, Recipient of the Chancellor's Award for Excellence in Undergraduate Research and Creative Achievement
2010 NSF Career Award
2009 Fulbright Scholarships
1/1/05 - 6/30/2008 UC Riverside, John Babbage Chair
2005 Regents' Faculty Fellowship/Faculty Development Award
2001-2004 U.S. Environmental Protection Agency STAR Fellowship
2003 American Chemical Society Certificate of Merit, Environmental Chemistry Division
2002 American Chemical Society Graduate Student Award in Environmental Chemistry
2000-2003 National Water Research Institute Graduate Fellowship
Dr. Walker's research interest lies at the intersection of physical, chemical, and biological processes in natural and engineered aquatic systems. In particular, work has focused on understanding the factors controlling bacterial adhesion and transport in subsurface environments. The emphasis has been to explore the fundamental mechanisms involved in cellular adhesion, and the interactions occurring at the molecular scale between the bacterium and mineral surfaces. These mechanisms apply to not only to bacterial-mineral interactions, but also between bacteria with surfaces such as membranes, filter media, and biomedical materials.
The overall goal of Dr. Walker's work is to optimize effective water treatment and distribution, wastewater reclamation, and to understand mechanisms controlling microbial transport in aquatic environments. Current research areas include the following:
Application molecular techniques to find possible links between genetic characteristics of bacteria and their adhesion and transport behavior, and expanding current predictive capability for transport of various bacterial species in aquatic systems.
Examination of the sensitivity of bacterial adhesion to physical and chemical fluctuations as would occur in natural (i.e. groundwater) and engineered (i.e. water and wastewater treatment plants) systems through the investigation of the removal of cells in a radial stagnation point flow (RSPF) system, a parallel plate (PP) flow chamber, and traditional packed bed columns.
Study of nanoparticle attachment and detachment kinetics in flowing systems.
Bolster, C.H., Haznedaroglu, B., and Walker, S. L. “Diversity in cell properties and transport behavior among 12 environmental Escherichia coli isolates” Journal of Environmental Quality (in press)
Tazehkand, S.S., Torkzaban, S., Walker, S.L., and Bradford. S.A. 2008 “Cell preparation methods influence E.coli D21g surface chemistry and transport in saturated porous media” Journal of Environmental Quality (in press)
Torkzaban, S., S. S. Tazehkand, S. L. Walker, and S. A. Bradford 2008, Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry, Water Resour. Res., 44, W04403, doi:10.1029/2007WR006541.
Torkzaban, S., Bradford. S.A., and Walker, S.L., 2008, “Colloid transport in unsaturated porous media: The role of water content and ionic strength on particle straining” Journal of Contaminant Hydrology 96:113-127
Haznedaroglu, B., Bolster, C.H., and Walker, S. L. , 2008, “The role of starvation on bacterial adhesion and transport in saturated porous media” Water Research 42:1547-1554
Torkzaban, S., Bradford. S.A., and Walker, S.L., 2007, “Resolving the coupled effects of hydrodynamics and DLVO forces on colloid attachment to collector surfaces” Langmuir, 23 (19), 9652 -9660. 10.1021/la700995e S0743-7463(70)00995-2
Chen, G. and Walker, S.L., 2007 “The role of solution chemistry and ion valence on the adhesion kinetics of groundwater and marine bacteria” Langmuir 23 (13) 7162-7169, doi:10.1021/la0632833
Bradford. S.A., Torkzaban, S., and Walker, S.L., 2007 “Coupling of physical and chemical mechanisms of colloid deposition in saturated porous media” Water Research 41: 3012-3024, doi:10.1016/j.watres.2007.03.030
Bradford. S.A., Simunek, J., and Walker, S.L., 2006 “Transport of E. coli O157:H7 in Saturated Porous Media” Water Resources Research, Special Section: Colloid Transport in Subsurface Environments 42 (12), W12S12, doi:10.1029/2005WR004805
Bolster, C.H., Walker, S.L., and Cook, K.L. 2006 “Comparison of Escherichia coli and Campylobacter jejuni Transport in Porous Media” Journal of Environmental Quality 35: 1018-1025
Walker, S.L. 2005 .The Role of Nutrient Presence on the Adhesion Kinetics of Burkholderia cepacia G4g and ENV435g. Colloids and Surfaces B: Biointerfaces 45: 181-188.
Walker, S.L 2005 ''The Influence of Bacterial Surface Polymers on Bacterial Adhesion and Transport in Groundwater Environments'' Journal of Harbin Institute of Technology (new series), 12: 19-26.
Walker, S.L., Redman, J.A., and Elimelech, M. 2005 .Influence of Growth Phase on Bacterial Adhesion and Transport: Interaction Mechanisms Involved in Packed-Bed Column and Radial Stagnation Point Flow Systems. Environmental Science and Technology, special issue .Particles and Interfaces in Aquatic Systems, A tribute to Prof. Charles R. O.Melia. 39: 6405-6411.
Walker, S.L., Hill, J., Redman, J.A. and Elimelech, M., 2005 "The Influence of Growth Phase on Adhesion Kinetics of Escherichia coli D21g. Applied and Environmental Microbiology, 71:3093-3099.