Soil Cleanup by In-Situ Aeration. XXI. Effects of Desorption Rates and Equilibria on Remediation Rates

Abstract

Abstract A model for soil vapor extraction (SVE) is developed which permits the use of nonlinear adsorption isotherms and takes desorption kinetics into account. The configuration modeled is a single vertical well. The model is used to exhibit the dependence of cleanup rate on the parameters of the nonlinear adsorption isotherm and on a rate constant k f associated with adsorption. Cleanup curves similar to those found in modeling diffusion-limited SVE by the lumped diffusion parameter method are observed for small values of k f. Slow cleanup rates can also result from isotherm parameter values. In particular, severe tailing in the terminal phase of remediation may result from an equilibrium isotherm which approaches the form C gas=K(C sorbed) B , where B > 1 as C sorbed approaches zero. As with diffusion-limited SVE, short-term pilot-scale experiments may well not identify conditions which cause tailing during terminal phase cleanup. One can distinguish between poor SVE performance due to small rate cons...