Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Danny D. Reible

Abstract

In evaluating risks associated with chemical spills on the ground surface or leaks from underground storage tanks, it is required to know the extent and degree of contamination in the subsurface. In many cases pure organics are spilled and due to their low miscibility with water they remain pure or concentrated for some distance or time from the source. This dissertation is aimed at developing a model of the multiphase (air, water, organic) migration processes. The particular focus is on modeling organic infiltration in the unsaturated zone where the transport is largely vertical. Sand-column experiments using a variety of immiscible and miscible organics indicated that the organic infiltration front after a 'spill' was sharp and that little residual water was displaced by an infiltrating immiscible organic. Based upon these assumptions, the multiphase transport problem was essentially modeled as a single phase infiltration under the influence of gravity and capillary forces. The resulting model describing organic phase infiltration rate contained two parameters, an effective medium permeability and an effective capillary suction at the wetting front. For the case of a fully infiltrated organic, an effective capillary suction at the drainage front was also required. The boundary element method (BEM) is used to solve the governing quasi-steady differential equations. Good agreement between the experimental data and the model was observed taking the effective medium permeability equal to the saturated flow permeability and using measured values of the capillary suction parameters. Many groundwater contamination incidents begin with the release of an essentially immiscible fluid into the subsurface environment. Once in the subsurface, an immiscible fluid participates in a complex pattern of transport processes. For immiscible fluids that are commonly found in contaminated groundwater environments the interphase mass transfer between the nonaqueous liquid phase and the aqueous phase is an important process. A model capable of exploring the effect of interphase mass transfer on in-situ extraction is also presented.

Pages

153

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