EVALUATION OF THERMAL EFFECTS ON THE DISSOLUTION OF A NONAQUEOUS PHASE LIQUID IN POROUS-MEDIA

Porous media contaminated with nonaqueous phase liquids (NAPLs) may se rve as a long-term source of groundwater contamination. To remove NAPL s and thereby mitigate the potential impact to the environment and hum an health, it has been suggested that contaminated media be flushed wi th cosolvents, surfactants, hot water, or steam. In this study, hot wa ter flooding was used to remediate a porous medium contaminated with t etrachlorethylene (PCE) at residual saturation in an otherwise water-s aturated medium. The effect of temperature on the physical and chemica l properties of the system was well characterized, and a quantitative assessment was made of the eff ect of temperature on PCE dissolution. A comparison of the results from the dissolution experiments with exis ting dimensionless correlations for NAPL dissolution in porous media e lucidated the role of the aqueous-phase viscosity and the NAPL species aqueous-phase diffusivity. Nonaqueous-aqueous phase mass transfer rat e coefficients measured for this system were put in dimensionless form (Sherwood number) and fitted to a power-law model. The Sherwood numbe r was found to vary with the Schmidt number to approximately the 0.5 p ower, as suggested by previous investigators. This result is expected to apply to nonaqueous-aqueous phase mass transfer in other systems wh ere aqueous-phase properties are altered by the addition of chemicals.