JOINT ELECTROOSMOTIC PURGING OF DNAPLS FROM SATURATED SOILS

The process of "pumping" water by electroosmosis has been used for dewatering and stabilizing soils since the 1930s, and has more recently been evaluated for treating groundwater contaminated with dossolved organics and toxic metals. Electroosmosis is particularly effective in fine pores where hydraulic pumping fails, particularly as its flow can be accurately directed. A modified process is proposed in which water is used to purge dense, non-aqueous phase (organic) liquids (DNAPLs) which are not normally susceptible to electroosmotic forces. An important advantage of this approach is that the purge liquid can be used to introduce surfactants that will enhance the rate of desorption and so remove absorbed DNAPLs that would otherwise continue to be a long-term source aquifer contamination. This in situ approach is expected to have energy costs of the order of $1/ton of soil treated and so offers significant cost savings over conventional extraction processes. The concept is to be demonstrated in a 10 ft3 test cell after determining operating parameters in a series of small-scale tests. In addition to the experimental investigation, the utility of a simplified theoretical model for design calculations and for predicting performance will be explored.