Complete Dissolution of Trichloroethylene in Saturated Porous Media

Porous media containing trichloroethylene (TCE) trapped at residual saturation in otherwise water-saturated porous media were flushed with water to assess the dissolution rate of TCE as TCE volumetric fractions approached zero. Careful attention to column design and experimental methods limited the effect of column materials on effluent concentrations. Effluent concentration measurements during TCE dissolution are presented for a glass bead porous medium, a mixed sand, and a treated soil. Effluent concentrations were measured as they decreased below 5 μg/L, the maximum allowable contaminant level, in the glass bead and mixed sand media. Effluent concentrations from columns packed with treated soil were measured down to 20 μg/L. Solvent extraction of the treated soil after the dissolution experiments revealed that extremely small quantities of TCE were retained in this medium. Results from parallel experiments on columns exposed to only aqueous TCE suggest that TCE remaining in the treated soil columns was sorbed to the porous medium. Existing power-law models were capable of describing TCE dissolution in these media, if the exponent on the TCE volume fraction was modified appropriately.