Nonaqueous phase liquid transport and cleanup: 2. Experimental studies

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Abstract
An analysis of the movement of nonaqueous liquids such as organic solvents and gasoline in part 1 (Hunt et al., this issue) showed that separate phase liquids are not completely displaced by groundwater flow under typical pumping conditions and that removal of the compounds by dissolution is mass transfer limited. Steam displacement was proposed as a more efficient cleanup strategy for separate phase organic liquids present in porous media. This paper presents the results of a series of laboratory sand column experiments designed to confirm the theoretical analyses presented in part 1 (Hunt et al., this issue). Experiments with trichloroethylene, a benzene‐toluene mixture, and a commercial gasoline, showed that water flow at rates as high as 15 m d−1 could not displace the separate phase liquids when present in a sand matrix in quantities corresponding to a column average saturation of 2.5%. Steam injection, on the other hand, displaced the contaminants as a separate phase just ahead of the steam front, producing a concentrated, small‐volume waste stream. Analysis of the laboratory data consisting of pressure gradients, temperature profiles, and water flow velocities shows that the laboratory results are consistent with the theoretical predictions. Moreover, computations of energy requirements show that steam displacement of separate phase contaminants is economically attractive.