Mathematical Modeling of In Situ Vapor Stripping of Contaminated Soils

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Abstract
Mathematical models are developed for evaluating the feasibility of in situ vapor stripping for the removal of volatile organics from contaminated soils. The models simulate both laboratory soil stripping columns and field‐scale vacuum extraction wells. Local equilibrium between the condensed and vapor phases is assumed for the volatile compounds; Henry's law or more complex isotherms may be used to describe this equilibrium. Methods for determining Henry's constants from lab data and for determining soil permeability from field data are presented. The models are used to predict the effects of well depth, Henry's constant, screened radius of well, and zone of influence radius. The use of impervious caps and passive vent wells to direct gas flow is discussed, and the effects of buried obstacles and evaporative cooling are examined. The possibility of recontamination from non‐aqueous phase liquid (NAPL) underlying the vadose zone is investigated, as is the ability of the vapor stripping technique to remove pools of NAPL floating on the water table below the vadose zone. An estimate of the maximum time required for cleanup at a site is made.
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