Comparison of one- and three-dimensional soil vapour extraction experiments

Soil vapour extraction (SVE) is a common remediation technology used to clean soil contaminated with gasoline. Even though many studies have been completed on SVE, the majority of them have been at the one-dimensional level, while SVE occurs at a three dimensional level. Accordingly, one-dimensional and radial column laboratory experiments were completed to determine if the experimental configuration made a difference with the results. Two soil types were tested at a variety of flow rates. The contaminant used was toluene. The results were analysed both qualitatively and quantitatively. Analysis of both systems showed them to provide good mass closures. On a qualitative basis, the one-dimensional experiments showed that an increase in flow rates did not result in significant mass transfer limitations for the air flow rates tested. The radial columns revealed mass transfer limitations that were not seen in the one-dimensional column. Quantitative comparison through back-calculated mass transfer coefficients confirmed the trends seen in the qualitative analysis. It is unclear if this is a result of geometry of the radial column or the higher velocities within the radial column. The results indicate that further work with the radial column is necessary to better understand field SVE systems, making it possible to better predict field performance.