Field demonstration of acoustically enhanced soil washing system for in-situ treatment of low-permeability soils

The objective of this research is the demonstration and explanation of an in-situ enhanced treatment/recovery technique that mobilizes contaminants in low-permeability soils. The technique uses ultrasonic excitation to stimulate contaminant migration. The ultrasonic excitation mechanically suspends fine particles to which the contaminants are strongly sorbed. Then the fine particles subsequently are recovered by induced hydraulic gradients. The recovery of these fines reduces the contaminant mass in the soil. Preliminary small-scale laboratory experiments suggest that the technique can homogenize soil at small scales and significantly affect their permeability. We have found that it will be important for the acoustic gradient and hydraulic gradient to be in opposite directions for the technique to be successful - a condition that was not anticipated prior to conducting the initial experiments. A laboratory study using fluorescent dyes and motor oil as 'contaminants' is currently in progress. A field demonstration using the dyes as 'contaminants' is planned and awaits a letter of authorization from the Texas Water Commission for an injection/recovery experiment.