Mixed region reactors for in situ treatment of DNAPL contaminated low permeability media

Fine-textured soils and sediments contaminated by dense non-aqueous phase liquids (DNAPLs) present a significant environmental restoration challenge. An emerging approach to rapid in situ treatment within low permeability media involves the use of soil mixing to create mixed region reactors wherein biological or physical/chemical treatment processes can be employed. In cohesive soils, mixing breaks up the original soil structure and produces soil aggregates or clods separated by interaggregate void spaces. These void spaces create preferential flow paths for more efficient extraction of contaminants from the soil matrix or more rapid diffusion of treatment agents into the soil aggregates. This enhancement technology has been most successfully used with vapor stripping. However, other technologies can also be coupled with soil mixing including chemical degradation, biodegradation and solidification. The application of this technology to DNAPL-contaminated low permeability media appears promising but requires further experiments and models that can simulate the movement of DNAPLs in mixed regions. 11 refs., 6 figs.