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Subsurface Compositional Simulation Incorporating Solute-Chemistry Dependent Constitutive Relationships: Implications for Site-Assessment and Remediation

EPA Grant Number: U915780
Title: Subsurface Compositional Simulation Incorporating Solute-Chemistry Dependent Constitutive Relationships: Implications for Site-Assessment and Remediation
Investigators: Phelan, Thomas J.
Institution: University of Michigan
EPA Project Officer: Thompson, Delores
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $102,000
RFA: STAR Graduate Fellowships (2000)
Research Category: Academic Fellowships , Fellowship - Engineering , Engineering and Environmental Chemistry

Description:

Objective:

Surface-active species, through their alteration of the constitutive relationships governing multiphase flow and transport, can have a significant impact on the fate and transport of organic non-aqueous phase liquids in the subsurface. These mechanisms can have important ramifications, hereunto neglected in practice, on conclusions regarding waste site assessment and ultimately, remediation. It is the intent of this research to incorporate the science described in the literature into a multiphase flow and transport simulator that incorporates solute chemistry effects on constitutive relationships.

Approach:

The equations governing multiphase flow and transport in the subsurface are highly nonlinear and strongly coupled. To model the temporal and spatial changes in fluid composition, the mass balance equations on dissolved components must be solved as well as the multiphase flow equations. The solution of this complete problem, in and of itself, requires tremendous computational resources. Addition of solute chemistry effects will compound this problem significantly. Incorporation of relative permeability, capillary pressure-saturation, and interphase mass transfer relationships that exhibit compositional dependence will increase the required computational effort markedly. The first step in this research, then, will be to develop an efficient computer code that solves the equations accurately and efficiently. The code being developed employs a two-dimensional Galerkin finite element method using chapeau basis functions on triangular elements to solve coupled phase and component mass balance equations.

Expected Results:

It is anticipated that the development of the computer code will be a major contribution of this research project. Once the code is developed, it must be verified against laboratory data in the literature. Can the data be simulated? If not, why not? Is the mathematical model insufficient? Are the parameters incorrect? These issues must be addressed before research can proceed. Assuming the computer model can adequately reproduce reality, a suite of simulations is planned to investigate the effects of solute-chemistry dependent parameters on field-scale scenarios. Questions to be answered include: What are the spatial and temporal scales at which these interfacial phenomena are important? Are they as important at the field scale as at the laboratory scale? For which types of problems are they important? Are they more important when one is considering flow or considering transport? Does neglecting these mechanisms introduce significant errors into estimates of off-site migration or remediation time? An interesting question to be examined is whether one can use the surface-active properties of certain solutes to induce capillary barriers to impede movement or to increase the dissolution rate of an organic contaminant.

Supplemental Keywords:

porous media, drinking water, groundwater, chemical transport, solvents, DNAPLs, NAPLs, surfactants, multiphase flow. , Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Waste, RFA, Remediation, Chemical Engineering, Civil/Environmental Engineering, Chemistry, computing technology, Environmental Engineering, Environmental Chemistry, Monitoring/Modeling, Civil Engineering, Ecology and Ecosystems, site remediation, site assessment, computer modeling programs, ecology assessment models, porous media, chemical transport, groundwater, NAPL, multiphase fluid flows, chemical transport model, DNAPLs, subsurface compositional simulation, multiphase flow and transport, ecology, analytical chemistry, non-aqueous phase liquids (NAPLs), modeling

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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