SOIL CLEAN UP BY IN-SITU AERATION .15. EFFECTS OF VARIABLE AIR-FLOW RATES IN DIFFUSION-LIMITED OPERATION

A model for soil vapor extraction (SVE) is developed which includes th e effects of mass transport kinetics of VOC between nonaqueous phase l iquid (NAPL) droplets and the aqueous phase, and between the aqueous a nd vapor phases. The model permits time-dependent gas flow rates in th e vapor extraction well. The model is employed to demonstrate the effe ctiveness of certain types of pilot-scale SVE experiments in determini ng the rate of mass transport processes. It is also used to explore se veral time-dependent air flow schedules for SVE well operation. The re sults indicate that the use of suitably selected air flow schedules in SVE can result in greatly reduced volumes of air to be treated for VO C removal with relatively little increase in the time required to meet remediation standards.