ABSTRACT
The selection of the surfactant system is one of the most critical steps in designing a successful surfactant flood. The surfactant chosen must solubilize and lower the interfacial tension between the contaminant and aqueous phases so that the DNAPL can be freed from the pore structure and displaced. Moreover, the surfactant must exhibit the appropriate phase behavior under the conditions expected in the target zone of the aquifer. The tendency to form gels, liquid crystals, and emulsions should be minimal, because surfactants prone to this type of behavior are likely to cause a loss of hydraulic conductivity due to plugging problems, present effluent treatment problems, and create phases that are difficult to recover hydraulically. In addition, the selected surfactant should also have a high contaminant solubilization capacity to maximize DNAPL recovery, and fast equilibration/coalescence times to minimize mass transfer and kinetic effects. Other desirable characteristics include no or very low toxicity, and the ability to biodegrade in a reasonable time frame (neither too quickly nor too slowly).
