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United States Department of Agriculture

Agricultural Research Service

Research Project: DETECTION, SOURCE IDENTIFICATION, ENVIRONMENTAL TRANSPORT, FATE, AND TREATMENT OF PATHOGENIC MICROORGANISMS DERIVED FROM ANIMAL WASTES Title: A New Paradigm for Pathogen Transport and Deposition in Porous Media: the Role of Pore Structure and Colloid-Colloid Interactions

Authors
item Walker, S.L. - U.C. RIVERSIDE, CA
item BRADFORD, SCOTT

Submitted to: Annual Colloid and Surface Science Symposium
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2006
Publication Date: June 18, 2006
Citation: Walker, S., Bradford, S.A. 2006. A new paradigm for pathogen transport and deposition in porous media: the role of pore structure and colloid-colloid interactions. Annual Colloid and Surface Science Symposium. Paper No. 14.

Technical Abstract: At present our ability to predict the transport and fate of pathogenic microorganisms in natural subsurface environments is limited by our understanding of the pathogen deposition process. A review of the literature has shown that the current paradigm for pathogen deposition, filtration theory, has serious flaws because it does not adequately account for the combined physical and chemical removal mechanisms involved in small pores, at colloid-colloid interfaces, and at colloid-grain interfaces. Therefore, a new conceptual model is presented that combines the influence of physical and chemical interaction mechanisms under unfavorable attachment conditions. Colloid association with the solid-water interface is described using interaction energies based upon traditional DLVO theory. Hydrodynamic forces can funnel weakly associated colloids into flow stagnation zones and grain-grain junctions; however, these same forces may also sweep colloids away from small pore spaces and into active flow pathways. The extent to which colloids pass through pore spaces is a function of the size of the colloid and pore, and the balance of hydrodynamic and DLVO forces, as the presence of an energy barrier effectively decreases the size of accessible pore space. The funneling of flow and retention of colloids in pores and grain junctions provides an optimum location for colloid-colloid interactions to occur such as flow induced aggregation. Experimental evidence that support this conceptual model of deposition is summarized. We believe this model will be useful for establishing a common framework for interpreting experimental results, and provides a basis for exploring the potential role of colloid-colloid interactions.

Last Modified: 9/10/2014
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