SANDTANK TESTING OF SURFACTANT ENHANCED REMEDIATION OF SUBSURFACE CONTAMINATION BY CHLORINATED SOLVENTS

DENSE NON-AQUEOUS PHASE LIQUIDS (DNAPLS) ARE A CLASS OF ORGANIC COMPOUNDS COMMONLY FOUND AS GROUND WATER CONTAMINANTS; CHLORINATED SOLVENTS ARE AN IMPORTANT CLASS OF DNAPLS. MANY DNAPLS ARE CHARACTERIZED AS BEING IMMISCIBLE WITH AND HEAVIER THAN WATER. THESE CHARACTERISTICS COMBINE TO MAKE SUBSURFACE DNAPL CONTAMINATION PARTICULARLY DIFFICULT TO REMEDIATE. IN GENERAL, DNAPLS RELEASED TO THE SUBSURFACE MIGRATE DOWNWARD LEAVING BEHIND RESIDUAL SATURATION CONCENTRATIONS IN THE UNSATURATED AND SATURATED ZONES. IF RELEASED IN SUFFICIENT QUANTITIES, THE DNAPL WILL FORM A FREE PHASE ON IMPERMEABLE MATERIALS AT THE BASE OF THE SATURATED ZONE. THE RESIDUAL SATURATION AND FREE PHASE DNAPLS IN THE SATURATED ZONE REPRESENT A LONG TERM SOURCE OF CONTAMINATION FOR GROUND WATER BECAUSE THEIR AQUEOUS SOLUBILITY IS MUCH HIGHER THAN THEIR ALLOWABLE DRINKING WATER STANDARD. THE KEY TO REMEDIATION IS REMOVAL OF THE RESITUAL AND FREE DNAPL FROM THE SUBSURFACE. SURFACTANTS IN SOLUTION CAN EMULSIFY OR SOLUBILIZE RESIDUAL OR FREE DNAPLS IN THE SATURATED ZONE IF SYSTEMS CAN BE DESIGNED WHICH WILL NOT EXPERIENCE SIGNIFICANT LOSSES DUE TO ADSORPTION OR PRECIPITATION. THE SURFACTANT SYSTEM MUST BE SELECTED BASED ON THE CHARACTERISTICS OF THE DNAPL, THE AQUIFER SOLID MEDIA, THE GROUND WATER, AND THE RESERVOIR TEMPERATURE IF IT IS TO BE EFFECTIVE. THE OBJECTIVES OF THE PROPOSED STUDY ARE TO ASSESS THE VIABILITY OF USING SUCH SURFACTANTS OR SURFACTANT SYSTEMS TO REMOVE FREE AND RESIDUAL SATURATIONS OF DNAPLS FROM SATURATED SOILS BY EITHER MECHANISM, EMULSIFICATION OR SOLUBIZATION, IN A TEN CUBIC FOOT TEST CELL.