ASSESSMENT OF IN-SITU SOLVENT-EXTRACTION FOR REMEDIATION OF COAL-TAR SITES - COLUMN STUDIES

Part of a study to assess the feasibility of coal tar site remediation by the injection and recovery of water-miscible, biodegradable solven ts is described. The overall objective of the study was to obtain esti mates of cleanup times and solvent volumes required for a hypothetical contaminated site. We describe the results of column experiments, per formed by passing solvent-water solutions through glass bead-packed co lumns contaminated with coal tar blobs at low volumetric saturation. T his experimental design allowed the investigation of dissolution rate limitations at residual saturations similar to those observed in the f ield, albeit under more homogeneous conditions. The column effluent da ta were modeled with a modified advection-dispersion equation that inc ludes a mass-transfer source term for coal tar dissolution. This sourc e term empirically relates mass transfer to experimental variables suc h as coal tar saturation and solvent flow velocity using fitting param eters. Values of parameters in the mass-transfer source term were esti mated from experimental data. The modeling approach and the parameter values developed in this study have been used in simulations of the in situ solvent extraction process.