In Situ Mixed Region Vapor Stripping in Low-Permeability Media. 3. Modeling of Field Tests

Abstract

A model was developed to simulate in situ mixed region vapor stripping process for removal of volatile organic compounds from fine-textured soils. The model consists of a thermal response submodel for simulating temperature, moisture content, and exhaust gas flow rate changes in the zone being treated and a mass transfer submodel for predicting the removal of a linearly sorbing, dissolved contaminant. The treatment zone was assumed to be completely mixed. Model parameters were obtained independently from measurements and literature correlations where possible. Calibration of first-order mass transfer rates and energy input (via soil mixing and high-pressure gas injection) was completed using the results of a full-scale field test. The calibrated thermal submodel predicted temperature changes observed in three other field tests. The model could simulate contaminant mass removal rates for the three independent tests. The mass transfer rates, ranging between 0.0009 and 0.0015 s -1 , were independent of temperature up to at least 30°C but appeared to be dependent on the frequency of contact between the mixing blades and various soil depths.