Soil Clean up by Venting: Comparison Between Modelling and Experimental VOC Removal Results

Abstract

Many investigations into specific or accidental pollution relate to hydrocarbons of oil origin: fuels (gasoline or gas oil), fuel oil and lubricants. Pollution by petroleum products is a source of volatile organic compounds in soil. Therefore, laboratory column venting experiments were completed in order to investigate the removal of a pure compound (toluene) and a mixture of two (toluene and n-heptane) and five (toluene, n-heptane, ethylbenzene, m-xylene and p-xylene) compounds. The choice of the compounds, as well as their proportion in the mixture was made on the basis of the real fuel composition. The objective of this study is a comparison between the experimental volatile organic compounds removal results and the predicted values of a simple classical analytical mathematical model that enables the modelling of the venting process. The proposed model for the contaminants transport describes the removal of organic compounds from soil, the contaminants being distributed among four phases: vapour, nonaqueous liquid phase, aqueous and "solid" phase; local phases equilibrium and ideal behaviour of all four phases were found to be accurate enough to describe the interphase mass transfer. The testing of the mathematical model accuracy has been done by using the following performance criteria: dynamic absolute error, average error, model accuracy and correlation coefficient. The reasonable agreement between the predicted and the experimental results as well as the values of the performance criteria prove that the mathematical model is suitable to describe the removal of volatile organic compounds pollutants by venting in the range of experimental conditions used in the pilot plant.