Fundamentals of Surfactant/Cosolvent Flushing

Aquifer remediation is frequently limited by oil contaminants capillary-bound in the aquifer material. Surfactant-enhanced subsurface remediation is an innovative technology for overcoming these limitations and thus expediting aquifer cleanup. Petroleum hydrocarbons and chlorinated solvents are common contaminants in soil and aquifer systems. Remediation of these hydrocarbons can be expedited by enhanced solubilization, using surfactant micellar systems, or by physical displacement (mobilization), resulting from ultra-low interfacial tension, middle phase microemulsion systems. Successful implementation of this technology requires detailed knowledge of surfactant chemistry and site-specific conditions (e.g., characteristics of the contamination, geology, water chemistry and heterogeneities). For chlorinated solvents, vertical migration concerns limit the use of middle phase microemulsions – for this application we utilize a hybrid system (super-solubilization), which maximizes the solubility enhancement while minimizing the potential for vertical migration. Economic analyses demonstrate that maximizing solubility enhancement, minimizing surfactant losses and reusing the surfactant stream are critical to the viability of the solubilization and mobilization technologies. This presentation will discuss each of these fundamental issues, with an emphasis on surfactant properties critical to success. Results from field studies demonstrate the viability and robustness of this technology for a wide range of contaminant matrices and geological settings, and illustrate the exciting potential of this innovative technology.