Surfactant Enhanced Mobilization of Nonaqueous Phase Liquids in Porous Media

Aquifers with dense nonaqueous phase liquids (DNAPLs) are difficult to remediate, due to the limited solubility of many DNAPLs in water and the immobility of residual DNAPLs at typical flow conditions of aquifers. Surfactant can be used to dramatically reduce remediation times via increased solubilization through micellar partitioning, increased mobilization through reductions in interfacial tension, or a combination of both. Different mobilization regimes result during surfactant flushing, but have not been examined for DNAPLs. Particular regimes are more easily controlled and are therefore preferred during surfactant flushing. Systems were studied in which capillary, viscous, and buoyancy forces were important to determine the critical conditions that lead to the different mobilization regimes during surfactant flushing. In these experiments, a 1:1 mixture of two food-grade, anionic surfactants, sodium diamyl sulfosuccinate and sodium dioctyl sulfosuccinate, were selected for the surfactant flushing solution, and tetrachloroethylene, a representative groundwater pollutant, was selected as the DNAPL. Experiments were conducted in two well-characterized cells packed with glass beads. Explanations of the mobilization regimes are given using a dimensionless grouping of system parameters (defined as the bank number). Because the bank number relies on general physical and chemical properties, it should be applicable to flushing of any homogeneous porous media. The pore-scale observations of this work have important implications concerning numeric simulations. The flow mechanism(s) that occur during flushing are important for determining the appropriate relative permeability function(s) used in numeric simulations.Master of Science in Environmental Engineerin