Experimental and Economic Assessment of Two Surfactant Formulations for Source Zone Remediation at a Former Dry Cleaning Facility

Abstract

AbstractTreatability tests and cost analyses were conducted to provide objective criteria for selection of a surfactant formulation to be used for surfactant enhanced aquifer remediation (SEAR) of a tetrachloroethene (PCE)‐contaminated site in Oscoda, Michigan. Two surfactant formulations, 4% Tween 80 + 500 mg/L CaCl2 and 8% Aerosol MA/IPA +15,000 mg/L NaCl + 1000 mg/L CaCl2, were considered based on their capacity to solubilize PCE and prior use in SEAR applications. Results of a two‐dimensional aquifer cell experiment indicated that 53% of the released PCE was recovered after flushing with approximately 8 pore volumes of 4% Tween 80. In contrast, only 3 pore volumes of 8% Aerosol MA/IPA solution were required to recover 78% of the PCE from the two‐dimensional aquifer cell, although the greater recovery of PCE was attributed, in large part, to the higher concentration of Aerosol MA. However, mobilization of PCE as free product was observed during the 8% Aerosol MA/IPA flood, which was consistent with total trapping number (NT) calculations. At the pilot‐scale, SEAR treatment costs were estimated to be $222,000 and $244,000 for 4% Tween 80 and 8% Aerosol MA/IPA, respectively, which compared favorably to the estimated pump‐and‐treat cost of $316,000. Projected full‐scale costs, based on a line‐drive flushing system, were $382,000 for 4% Tween 80 and $443,000 for 8% Aerosol MA/IPA. In contrast, full‐scale pump‐and‐treat costs were estimated to be $1,167,000. Surfactant recycling was shown to be logistically and economically infeasible at the pilot scale, and provided only a minimal cost benefit for 4% Tween 80 at the full scale. Based on the similarities in solubilization capacity and treatment cost, but substantially lower risk of PCE displacement, Tween 80 was recommended over Aerosol MA/IPA for pilot‐scale testing of SEAR.