Modeling vapor extraction and general transport in the presence of NAPL mixtures and nonideal conditions
- Applied Geosciences, Inc., Irvine, CA (United States)
- San Diego State Univ., CA (United States)
- Westhollow Research Center, Houston, TX (United States)
The design of vapor-extraction remedial systems and the analysis of their performance can be improved by using models that can simulate the chemical and physical processes affecting the occurrence and movement of multiple-compound vapor-phase chemical mixtures. Previous models fall into two categories: (1) multiple-compound phase distribution models which are either nondimensional (no transport) or one-dimensional (column experiments); and (2) multidimensional single-compound transport models. In this paper, a model is presented that couples the steady-state vapor flow equation, the advection-diffusion transport equation, and a multiple-compound, multiphase chemical partitioning model. The numerical implementation allows spatially variable fields of permeability, confining layer permeability, and initial contaminant concentrations. Based on the concentrations of each chemical compound, the model calculates whether a nonaqueous phase liquid (NAPL) is present, and calculates the chemical phase distribution by the appropriate equilibrium partitioning formulation (Henry's Law or Raoult's Law). The user can specify the location and discharge rates of any number of extraction or injection wells, including zero wells, in which case the simulation will solve transport by diffusion only. The remediation, by vapor extraction, of hypothetical fuel hydrocarbon spills was simulated to investigate the error introduced by failing to account for natural conditions. The nonideal conditions include inhomogeneous soil permeability, leakage of atmospheric air into the subsurface and irregular contaminant distribution. The model was also run in the pure diffusion mode to simulate the transport of benzene to the ground surface, and to show the limitations of single-compound vapor flux models when a multicompound NAPL (such as gasoline) represents the source of benzene.
- OSTI ID:
- 6489546
- Journal Information:
- Ground Water; (United States), Vol. 31:3; ISSN 0017-467X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
BENZENE
ENVIRONMENTAL TRANSPORT
MATHEMATICAL MODELS
GROUND WATER
CONTAMINATION
PETROLEUM
EXTRACTION
FLUID FLOW
MIXTURES
OIL SPILLS
PERMEABILITY
REMEDIAL ACTION
VAPORS
WATER POLLUTION
AROMATICS
DISPERSIONS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
GASES
HYDROCARBONS
HYDROGEN COMPOUNDS
MASS TRANSFER
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
POLLUTION
SEPARATION PROCESSES
WATER
020900* - Petroleum- Environmental Aspects
540220 - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)