Monday, March 31, 2008 : 2:20 p.m.
Virus Retention and Transport in Porous Media
The safety and quality of the nation’s water supply are of great public concern. Human pathogenic viruses have been found in wells and drinking water due to improper placement of wastewater disposal operations and land application of wastewater and sewage sludge. Approximately 70% of outbreaks of waterborne diseases in the United States are associated with groundwater contaminated by pathogenic microorganisms. Therefore, understanding the fate and transport of viruses in soil and groundwater is vital for designing protective zones around water supply wells and developing regulations such as the Ground Water Rule. Our studies have shown that the fate and transport of viruses in natural environments are substantially determined by properties of porous media, solution chemistry, and virus strains. Metal oxides play an important role in virus sorption and inactivation, particularly those with large zero point of charge. The effects of metal oxides depend on solution chemistry and virus strains. Both solution ionic strength and pH affect virus attachment. However, change in ionic strength does not cause virus inactivation, for instance, on montmorillonite and alumina, whereas viruses lose infectivity at low pH. Anions also affect virus-surface interactions. Presence of phosphate on solid surface or in solution prevents viruses from attachment and inactivation during transport, particularly for the viruses with low isoelectric point (e.g., MS- 2). Conversely, presence of carbonate enhances virus attachment and inactivation because adsorption of carbonate at porous medium provides additional protonated surface sites for extra sorption of viruses. Interestingly, the effect of organic materials is relatively complex, depending on virus type, hydrophobicity of organic matter, and levels of metal oxides at solid surfaces. In general, dissolved organic matter competes for sorption sites with viruses resulting in less attachment of viruses, and mineral-associated organic matter influences virus transport dominantly through electrostatic rather than hydrophobic interactions.
Joe Zhuang, Ph.D., The University of Tennessee Dr. Zhuang is a Research Assistant Professor at the University of Tennessee Institute for a Secure and Sustainable Environment (ISSE). His research interests include experimental investigations of transport of colloids and microorganisms in the subsurface, as well as nanoparticles, environmental chemistry and hydrologic tracers.