IN SITU AQUIFER RESTORATION FROM DENSE SOLVENT CONTAMINATION BY STEAM INJECTION

STEAM INJECTION IS PROPOSED AS A TECHNOLOGY WHICH CAN ENHANCE THE APPLICATION OF THE PUMP-AND-TREAT, SOIL VENTING, AND BIOREMEDIATION TECHNOLOGIES IN THE CLEANUP OF AQUIFERS CONTAMINATED BY DENSE SOLVENTS. THE USE OF STEAM INJECTION TO REMEDIATE VADOSE ZONE CONTAMINATION HAS BEEN FIELD-TESTED SUCCESSFULLY. AQUIFER CLEANUP IS CONCEPTUALLY VIABLE BUT REMAINS UNPROVEN. IN A CONCEPTUAL CLEANUP, VERTICAL STEAM INJECTION WELLS SURROUND THE REGION OF CONTAMINATION AND EXTRACTION WELLS ARE PLACED WITHIN THIS REGION. STEAM IS INJECTED BOTH ABOVE AND BELOW THE WATER TABLE. THE STEAM INJECTION PRESSURE MUST BE HIGHER THAN THE HYDRAULIC PRESSURE OF THE AQUIFER TO ENABLE INJECTION. IN THE EXTRACTION WELLS, GROUNDWATER AND PRODUCT ARE REMOVED AND A VACUUM IS APPLIED. THIS AIDS IN DIRECTING THE STEAM TOWARD THE EXTRACTION WELLS. THE SOIL IS HEATED AS THE STEAM CONDENSES UNTIL IT REACHES STEAM TEMPERATURE CREATING A STEAM ZONE. THIS STEAM ZONE GROWS TOWARD THE EXTRACTION WELLS AND PUSHES MUCH OF THE CONTAMINANT AHEAD OF IT. IN THE STEAM ZONE, THE RESIDUAL CONTAMINANT IS VOLATILIZED AT THE ELEVATED TEMPERATURE AND SWEPT TOWARD THE EXTRACTION WELL BY THE FLOWING STEAM. AFTER STEAM BREAKS THROUGH IN THE EXTRACTION WELLS, THE INJECTION CONTINUES UNTIL RECOVERY OF CONTAMINANTS DIMINISHES.