IMPORTANCE OF PHASE-BEHAVIOR ON THE REMOVAL OF RESIDUAL DNAPLS FROM POROUS-MEDIA BY ALCOHOL FLOODING

A promising method of accelerating the removal of residual DNAPLs from aquifers involves the mobilization of trapped globules by alcohol flo oding. This technology was originally developed in the petroleum indus try for the recovery of residual oil after waterflooding. Alcohols can significantly reduce the interfacial tension between the residual DNA PLs and the aqueous phase, allowing for mobilization of trapped globul es through pore constrictions. In addition, laboratory batch and colum n results show that certain alcohols preferentially partition into the DNAPL phase, swelling the residual DNAPL globules considerably and at the same time reducing their density significantly. The swollen DNAPL globules become a relatively continuous phase during flooding, making them much easier to displace than disconnected residuals. Density red uction makes the mobilized DNAPL easier to control, and reduces the po tential for further downward migration into uncontaminated portions of the aquifer. Laboratory column results confirm that residual trichlor oethylene and tetrachloroethylene globules can be effectively removed from glass bead packings at low upflow gradients using preferentially DNAPL-soluble alcohols.