Modeling the Influence of Heat/Moisture Exchange during Bioventing

Abstract

The presented modeling investigation examines the potential influence of advection-induced evaporation and condensation on bioventing, a vadose-zone remediation technology. Currently, few soil vapor extraction or bioventing models incorporate nonisothermal effects when considering system performance. Laboratory and field measurements suggest, however, that even small changes in temperature and moisture content can influence microbial activity and could thus affect the overall efficiency of a bioventing operation. The model here is a one-dimensional simulator that describes mass and energy transport under steady, gaseous phase flow conditions. The coupled mass and energy equations are solved using a sequential iterative solver with matric potential and temperature as primary variables. A literature-derived relation is used to quantify the combined effect of water potential and temperature change on biological growth rates. Simulations indicate that the injection of air at temperatures and/or water vapor concentrations different from the initial ambient soil conditions can induce changes in matric potential and local soil temperature, which could measurably impact biological activity.