Date of Award

Spring 2017

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. Daniel P. Cassidy

Second Advisor

Dr. Duane R. Hampton

Third Advisor

Dr. Donald M. Reeves

Keywords

Surfactant, Saponin, NAPL, contamination, push-pull

Access Setting

Masters Thesis-Open Access

Abstract

Laboratory studies were conducted on Quillaja saponins and nine other surfactants commonly used to remove non-aqueous phase liquids (NAPLs) from soils and aquifers. The NAPL contaminant tested was diesel fuel. Static batch reactors containing an aged diesel-contaminated soil was treated with saponins and nine other commercially available surfactants to determine how much diesel fuel could be removed with the pore fluids after 1 day and 10 days of contact time. Of all the surfactants tested, saponins achieved the greatest removal of diesel fuel after 1 day and 10 days. There was large disparity in the diesel fuel removed by the other nine surfactants tested, which suggests a high degree of specificity controlled by the soil, rather than the NAPL itself. The amount of diesel fuel removed was much greater after 10 days than after 1 day, which demonstrates the importance of allowing contact time after introducing surfactants into a NAPL contaminated system, especially one with little or no mixing.

Column studies were then conducted with saponins as the only surfactants, with and without co-injection with hydrogen peroxide (H2O2). Because mixing has been shown to enhance contact between NAPL and surfactants, and therefore NAPL removal, H2O2 was tested as a co-injectate that could provide mixing in the pores of the columns because of its tendency to auto-decomposition to O2 gas on soils. Columns were used to simulate a Push-Pull application of surfactants, which is increasingly being used for small NAPL contaminated sites (e.g., gasoline stations). The columns were charged with Ottawa sand (20-30 mesh) that had been artificially contaminated with diesel fuel and mixed every month over a year-long period. Two doses of saponins were injected (500 times and 1000 times the critical micelle concentration) alone and with a 5% H2O2 solution. When injected alone, the higher dose of saponins achieved greater NAPL removal than the lower dose. For both saponin doses tested, NAPL removal was significantly enhanced when co-injected with H2O2. The greatest removal achieved was when a solution of saponins 1000 times the CMC was injected in a 5% hydrogen peroxide solution. The results suggest that injecting saponins with low concentrations of H2O2 has the potential to enhance surfactant-enhanced NAPL recovery in Push-Pull applications in the field.

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