Three models for the operation of surfactant washing/flushing columns or test beds are developed. These differ in the manner in which hydrophobic contaminant is held in the soil and, therefore, in the nature of mass transfer of contaminant from the stationary phase to the advecting surfactant solution. The fitting of parameters to experimental results is addressed, following which the parameters obtained are used to simulate operation of laboratory columns and a pilot-scale test bed. The results are compared which experimental data from the column and test bed. The air stripping of biphenyl from spent surfactant solution is modeled using a local equilibrium approach to see if air stripping could account for observed losses. The air stripping of toluene from the surfactant solution is modeled using a local equilibrium approach or a lumped parameter method to model diffusion-limited kinetics.