AN EXPERIMENTAL INVESTIGATION OF NONAQUEOUS PHASE LIQUID DISSOLUTION IN SATURATED SUBSURFACE SYSTEMS - TRANSIENT MASS-TRANSFER RATES

This work focuses on the experimental measurement and mathematical mod eling of processes affecting the dissolution of nonaqueous phase liqui ds (NAPLs) entrapped in sandy porous media. Results of a series of lab oratory-scale one-dimensional column dissolution experiments indicate that the length of time required to dissolve NAPLs and substantially r educe aqueous phase effluent concentrations is many times greater than predicted by equilibrium calculations. Experimental measurements clea rly show an influence of both grain size and grain size distribution o n the evolution of effluent concentrations. The longer cleaning times associated with coarse or graded media are attributed to the larger an d more amorphous NAPL blobs associated with these media. A general cor relation for transient dissolution rates is proposed which incorporate s porous medium properties, Reynolds number, and volumetric fraction o f NAPL. The model is calibrated with results from styrene dissolution experiments and is shown to adequately predict trichloroethylene disso lution rates in the same sandy media over the period of time required to dissolve the NAPL.