Dilution Effect of the Apparatus on Contaminant Transport Parameters Assessed by Column Testing

This technical note describes a method aimed at correcting the dilution effect of the apparatus on the solute transport parameters determined by column testing. The method requires quantification of the dead volume (i.e., not drainable during sample collection) of the permeation apparatus and makes use of a closed-form solution to the advection-dispersion-reaction equation (ADRE) equation used to infer transport parameters from column test results. Simulations of the dilution effect were performed and actual experimental data were analyzed, with reference to testing equipment frequently used in column studies (flexible-wall permeameter and bladder accumulators) and to porous materials commonly used in pollutant containment [geosynthetic clay liners (GCLs) and compacted clay liners (CCLs)]. Results showed that the dilution effect of the testing apparatus can significantly affect the determined transport parameters, in particular by increasing the retardation factor and reducing the diffusion coefficient. (C) 2015 American Society of Civil Engineers.