Surfactant-Enhanced DNAPL Removal

Due to the limitations of conventional groundwater remediation technologies, innovative methods have been sought to enhance the removal of recalcitrant compounds such as trichloroethylene TCE and tetrachloroethylene PCE, which are frequently trapped in the subsurface as dense nonaqueous phase liquids DNAPLs. Surfactant-Enhanced Aquifer Remediation SEAR is one such method, which has been adapted from enhanced oil recovery techniques used by the petroleum industry. It involves sweeping a surfactant solution across the DNAPL-contaminated portion of the aquifer. The surfactants accomplish rapid removal of the DNAPL contaminant by greatly increasing its effective aqueous solubility and by reducing the interfacial tension between the DNAPL and water phases. In field demonstrations conducted to date, up to 99 removal efficiencies have been achieved with just three pore volumes of surfactant followed by water flooding. In a typical remediation scheme, surfactants are used to remediate DNAPL source areas and complement the use of other technologies, such as conventional pump- and -treat systems, for removing the dissolved-phase plumes that are associated with DNAPL source areas. Currently, simple options for remediating DNAPL source areas are limited. Residual DNAPL in an aquifer acts as a continual source of contamination to the groundwater, and site closure cannot be achieved unless the source is removed. This surfactant-based technology will be more cost-effective than conventional pump-and-treat systems and will provide for a more rapid site cleanup.