Cost-Benefit Analysis of Cosolvent Flushing to Treat Groundwater Contamination Source Areas

Dense non-aqueous phase liquids (DNAPLs) in the zone beneath the water table can be a virtually permanent source of groundwater contamination that cannot be remediated by currently available technologies. Cosolvent flushing is a new technology that has the potential to remediate these sites and could pose a solution to the problem of DNAPL source areas. A computer model was developed to determine the cost and time to remediate an aquifer using cosolvent flushing. Included in the model is a module to calculate the costs of recycling the alcohol that is used as the cosolvent. The model was validated using site conditions to a prior study. It was determined that recycling the cosolvent allows cosolvent flushing to be a cost effective alternative to surfactant flushing, another new technology being considered for DNAPL source remediation. Sensitivity analysis of the model was conducted by varying the saturation percentage of contaminant, percentage and type of alcohol used in the cosolvent mixture, site hydraulic conductivity, and the contaminant. Five alcohols were modeled: methanol, ethanol, 1-isopropanol, 2-isopropanol, and tert-butyl-alcohol (TBA). 1-Isopropanol, 2-isopropanol, and TBA were always more expensive than methanol and ethanol