Enhanced anaerobic bioremediation of chlorinated solvents utilizing vegetable oil emulsions
The use of vegetable oil as an electron donor to enhance the reductive dechlorination of chlorinated solvents as an in situ remediation technology is gaining significant traction. Vegetable oil is a cost-effective slow-release electron donor with greater hydrogen-release efficiency than other electron-donor products. However, neat vegetable oil can inhibit distribution in aquifers due to the oil droplets blocking the flow of groundwater through the smaller pore spaces in the aquifer materials. This issue has been partially overcome by applying the vegetable oil as an oil-water emulsion, which typically is created in the field. However, the field preparation results in a mixture of droplet sizes, including larger droplets that can make the emulsions unstable and reduce the soil permeability by blocking soil-pore throats with oil. RNAS, Inc., has developed a kinetically stable soybean oil emulsion ('Newman Zone') consisting of submicron droplets with less droplet size variation than field-prepared emulsions. This product is composed of a blend of fast-release (sodium lactate) and slow-release (soybean oil) electron donors. The emulsion is produced in a stable factory environment in which it is pasteurized and packaged in sterile packaging. This material can be utilized as an electron donor without further treatments or amendments in the field. This article discusses factors associated with selecting electron donors and the development of vegetable oil-based products. A case study of an application of Newman Zone at a former adhesives manufacturing facility is then presented. The case study demonstrates the effect of Newman Zone in reducing chlorinated solvent concentrations in groundwater by both rapidly stimulating initial microbial activity and supporting long-term reductive dechlorination with a slow-release electron donor. O 2006 Wiley Periodicals, Inc.