Trichloroethylene (TCE) is a widespread pollutant and is reported to be the most frequently encountered contaminant at hazardous waste sites. All previous attempts at in situ bioremediation have used a process where methanotrophic bacteria were stimulated by the subsurface delivery of air and methane resulting in a "fortuitous" cometabolism of TCE. This process at one time appeared promising for the in situ bioremediation of TCE, but only limited success has been achieved and no field site has been bioremediated to EPA acceptable levels. This limited success is primarily due to physical problems associated with delivering sufficient levels of methane and oxygen which are very insoluble. Therefore, an innovative approach to in situ bioremediation would be to facilitate TCE cometabolism by using highly soluble compounds. Nitrifying bacteria elaborate an enzyme (ammonia oxygenase) that is a broad specificity oxygenase similar to the broad specificity enzyme elaborated by bacteria stimulated by methane and air. Also some heterotrophic bacteria can elaborate ammonia oxygenase while simultaneously respiring with nitrate thus decreasing their oxygen requirements. The objective of this proposal is to stimulate TCE cometabolism by stimulating heterotrophic bacteria that can simultaneously nitrify and denitrify using the water soluble compounds, ammonia, nitrate, and acetate.
