Enhanced Contaminant Remediation: Fermentation as a Method to Enhance Dissolution of Hydrophobic Compounds
Principal Investigator: Paige Novak, Associate Professor, Department of Civil Engineering, University of Minnesota
USGS-WRRI 104B/ CAIWQ Competitive Grants Program
March 2007 - February 2008
Recently researchers have been working to develop innovative technologies to address both sorbed phase contaminants and non-aqueous phase liquid (NAPL) source areas in situ. Among these technologies are Surfactant-Enhanced Aquifer Remediation and cosolvent flooding. Both of these technologies involve the injection of chemicals into an aquifer in a manner designed to flood the impacted zone, thereby mobilizing sorbed contaminant mass and NAPL (ITRC, 2002). The mobilized contaminant is subsequently extracted and treated ex situ. Although effective, these methods depend on our ability to adequately contact the contaminants with surfactants or cosolvents. This can be a challenge, and it typically addresses by adding large quantities of chemical in the hope that this will facilitate contact. A novel, and perhaps a better method of cosolvent and/or biosurfactant delivery, is through the stimulation of naturally occurring organisms that produce various cosolvents and biosurfactants in situ through fermentative processes. These processes can be stimulated by the addition of readily degradable carbon sources (i.e. sugars) to the aquifer. Multiple fermentation pathways exist, each yielding a particular set of end products, including alcohols, ketones, volatile fatty acids, and gases. It is hypothesized that the combination of cosolvents and biosurfactants that are produced in situ during fermentation can contribute to the release of sorbed contaminants and aid in the dissolution of NAPL present within the aquifer. In the case of trichloroethene (TCE), application of a carbon source will also promote enhanced reductive dechlorination, a process in which TCE is reduced to benign end products through microbial degradation. Therefore the application of carbon will achieve two objectives: (1) aid in the dissolution of NAPL and sorbed mass, and (2) stimulate the indigenous microbial community to degrade the released mass. Although a great deal of research has focused on the later, no laboratory studies have addressed the former. We propose that an accelerated cleanup of lingering source areas can be achieved by optimizing the production of cosolvents and biosurfactants via fermentation processes. Therefore, we propose to investigate how the supply of various carbon sources to soil impacts the production of cosolvents and biosurfactants through fermentation. The effect of these compounds on the solubility of a common hydrophobic contaminant, TCE, will also be determined through simple solubility experiments.