Evaluating DNAPL Dissolution Kinetics During Chemical Oxidation in An Experimental Fracture Network

Tuesday, April 13, 2010
Kaneen Elizabeth Christensen , Environmental Science and Engineering, Colorado School of Mines, Golden, CO
Peggy Altman , Environmental Science and Engineering, Colorado School of Mines, Golden, CO
Dr. John McCray , Environmental Science and Engineering, Colorado School of Mines, Golden, CO
Charles E. Schaefer, Ph.D. , Shaw Environmental and Infrastructure Inc., Lawrenceville, NJ
In situ chemical oxidation (ISCO) is an increasingly common remedial strategy used  to address groundwater sites contaminated with dense non-aqueous phase liquids (DNAPLs). ISCO is typically used at contaminated site to increase mass transfer from DNAPL phase to the aqueous phase. At these contaminated groundwater sites, DNAPLs can penetrate deep into the subsurface and into the underlying fractured bedrock, adding to the complexity of addressing DNAPL contaminated aquifers. However, the kinetics of DNAPL dissolution in fractured-aquifer systems under ISCO amendments has not been studied in detail. This research is the first to investigate aqueous DNAPL dissolution during ambient groundwater conditions as well as DNAPL dissolution during chemical oxidation in a three dimensional (3-D) fractured sandstone network experiment.

The DNAPL dissolution mass transfer rates during ambient groundwater flow and ISCO will be compared to a discrete fracture study and comparable porous media experiments utilizing chemical oxidation. All experimentally derived mass transfer rates will be evaluated against system properties to determine the primary factors controlling dissolution in fractured-aquifer settings, these include:  interfacial area, Reynolds number (lumped parameter that includes velocity and liquid properties), and other measures of the fracture network characteristics. The experimental goal utilizing the 3D fracture network is to develop a constitutive, empirical, or phenomenological model to yield predictive methods for contaminant-source longevity regarding DNAPL dissolution as well as improve understanding of DNAPL dissolution during ISCO in these complex fractured-aquifer groundwater settings.