Evaluation of thermal effects on the dissolution of a nonaqueous phase liquid in porous media

Porous media contaminated with nonaqueous phase liquids (NAPLs) may serve as a long-term source of groundwater contamination. To remove NAPLs and thereby mitigate the potential impact to the environment and human health, it has been suggested that contaminated media be flushed with cosolvents, surfactants, hot water, or steam. In this study, hot water flooding was used to remediate a porous medium contaminated with tetrachlorethylene (PCE) at residual saturation in an otherwise water-saturated medium. The effect of temperature on the physical and chemical 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 existing dimensionless correlations for NAPL dissolution in porous media elucidated the role of the aqueous-phase viscosity and the NAPL species aqueous-phase diffusivity. Nonaqueous-aqueous phase mass transfer rate coefficients measured for this system were put in dimensionless form (Sherwood number) and fitted to a power-law model. The Sherwood number was found to vary with the Schmidt number to approximately the 0.5 power, as suggested by previous investigators. This result is expected to apply to nonaqueous-aqueous phase mass transfer in other systems where aqueous-phase properties are altered by the addition of chemicals.