Influence of water evaporation on soil vapor extraction (SVE)

As SVE proceeds large amounts of water are withdrawn from the soil with the gaseous stream together with the contaminants. This may lead to important variations in the pneumatic soil permeability and changes in the soil temperature. A one-dimensional column mathematical model is developed to study these effects, based on the Millington and Quirk expression and assuming local thermal equilibrium and fast water mass transfer from the condensed to the gaseous phase. This model yields a good agreement with experimental results obtained with fine-sand lab columns. The molar flux increases during the process, but most of this increase takes place during the latter period of the drying process. Important temperature drops (up to 10 °C) are also expected when relative moisture of the air is low.