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Modeling field-scale cosolvent flooding for DNAPL source zone remediation
Hailian Liang1, Ronald W Falta
1Department of Environmental Engineering and Earth Science, Clemson University, Clemson, SC 29634-0919, USA.
Journal of Contaminant Hydrology
|November 9, 2007
Summary
Cosolvent flooding effectively removes dense non-aqueous phase liquid (DNAPL) contaminants like tetrachloroethylene (PCE) using ethanol. Site heterogeneity and contaminant distribution require model calibration for accurate remediation predictions.
Area of Science:
- Environmental Engineering
- Hydrogeology
- Chemical Engineering
Background:
- Dense non-aqueous phase liquid (DNAPL) contamination poses significant environmental challenges.
- Remediation of DNAPL sites often involves complex multiphase flow dynamics.
- Tetrachloroethylene (PCE) is a common and persistent DNAPL contaminant.
Purpose of the Study:
- To model and assess the effectiveness of cosolvent flooding for DNAPL (PCE) removal at a field scale.
- To investigate the impact of high ethanol concentrations on DNAPL dissolution and transport.
- To evaluate the role of porous media heterogeneity and DNAPL distribution in remediation efficacy.
Main Methods:
- Utilized a three-dimensional, compositional, multiphase flow simulator (UTCHEM).
- Modeled a ternary ethanol-PCE-water system, accounting for equilibrium phase behavior and multiphase flow.
- Employed a kinetic interphase mass transfer approach and performed field simulations in three calibration steps.
Main Results:
- High ethanol concentrations (>95%) led to a single-phase mixture, rendering mass transfer limitations irrelevant.
- Initial models struggled to accurately predict PCE removal, highlighting the impact of site-specific parameters.
- Calibrating the initial PCE distribution was crucial for matching effluent curves and predicting removal.
Conclusions:
- Cosolvent flooding is a viable strategy for DNAPL remediation, particularly with high ethanol concentrations.
- Spatial heterogeneity of porous media and uncertainty in DNAPL distribution are critical factors influencing remediation success.
- Model calibration, especially for initial contaminant distribution, is essential for accurate field-scale remediation predictions.
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