VEGETABLE OIL DELIVERY TECHNIQUES FOR USE AS A CARBON SOURCE IN THE REDUCTIVE DECHLORINATION OF CHLORINATED SOLVENTS IN SATURATED POROUS MEDIA

Organic waste chemicals that are in the form of dense non-aqueous phase liquids (DNAPL’s) are found at many contaminated sites. There physical properties in combination with geologic heterogeneities create complex NAPL entrapment morphologies in the subsurface. Conventional remediation methods such as pump-and-treat have proven to be costly and relatively ineffective methods of treating source zone contamination. Therefore in-situ methods such as bioremediation in the form of reductive dechlorination are actively being evaluated for treatment. One setback of the reductive dechlorination process is that it involves the injection of costly, soluble electron donors into the contaminant source zone. Current research is leaning towards cheaper substrate alternatives. Soybean oil emulsified with water and a byproduct called lecithin is an inexpensive, innocuous, food-grade carbon source that is being used in field applications. The soybean oil emulsion mixture itself is a lighter than water NAPL and exhibits the same behavioral complexities, leading to difficulties in predicting delivery efficiencies, in the field. The emulsion with oil droplets ranging from 1 to 15µm in size can disperse more readily into saturated field soils. The transport of these oil droplets can be predicted using a colloidal theory that combines the mathematical principals of Brownian motion, filtration theory, and the basic kinetics of the advection-dispersion and mass balance equations. A correlation between mean particle diameter and pore throat size can be made to determine which of the three transport phenomena - buoyancy, interception, or Brownian motion - will dominate the dispersion of these particles. Intermediate-scale test tanks packed with well characterized sands will be used to inject the oil emulsion(s) followed by non-partitioning tracers in an effort to develop and test this transport theory. Once the basic correlation has been made between pore size and particle size, simple predictive measures can be made to evaluate heterogeneities in soils, and oil droplet size distributions in an effort to aid field delivery techniques.