State Water Resources Research Institute Program

Project ID: 2009OH104B
Title: Evaluating Colloid Release from Natural and Model Porous Media
Project Type: Research
Start Date: 10/01/2009
End Date: 9/30/2010
Congressional District: Fifteenth
Focus Categories: Groundwater, Toxic Substances, Hydrology
Keywords: Toxic Substances, Water Chemistry, Geochemistry, Solute Transport, Ground Water Quality, Colloid Transport, Particle Filtration
Principal Investigator: Lenhart, John
Federal Funds: $ 10,424
Non-Federal Matching Funds: $ 20,912
Abstract: Colloidal processes are important in many natural and engineered systems. In natural systems, colloids present a potential health risk due to their propensity to associate with contaminants or in the case of certain biological colloids, inherent pathogenic nature. If stable in solution these colloidal particles and any co-adsorbed contaminants can be transported significant distances. Although colloidal interactions have been studied for many years and much has been learned about the physical and chemical processes that control irreversible colloid deposition, there still remains significant uncertainty about the processes that govern reversible deposition. Under steady and uniform flow, colloid stability can be estimated using DLVO-theory by summing van der Waals and Coulombic interactions. In systems comprised of surfaces with opposite charge, DLVO-theory is in general agreement with experimental results; however, discrepancies between experimental results and theoretical predictions are the rule, not the exception, in systems characterized by like-charged surfaces. Possible explanations for these discrepancies between theory and observation include surface roughness, charge heterogeneity, and the influence of the secondary minimum. Recent experimental and theoretical results highlight the importance of the secondary minimum, and suggest that it may dominate colloid interactions in many natural and engineered systems.

My objective is to examine reversible colloid deposition under unfavorable conditions in systems with like-charged surfaces. Work will combine experimental and computational tasks. Experimental data will be collected examining the deposition and subsequent release of spherical model colloid through sand-packed columns under a variety of conditions. Theoretical models will be developed and rigorously tested to appropriately incorporate the mechanisms responsible for reversible colloid deposition within the general framework of colloid-filtration theory.

Progress/Completion Report, 2009, PDF
Progress/Completion Report, 2010, PDF

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