EFFECTS OF NUTRIENT DOSING ON SUBSURFACE METHANOTROPHIC POPULATIONS AND TRICHLOROETHYLENE DEGRADATION

In in situ bioremediation demonstration at the Savannah River Site in Aiken, South Carolina, trichloroethylene-degrading microorganisms were stimulated by delivering nutrients to the TCE-contaminated subsurface via horizontal injection wells, Microbial and chemical monitoring of groundwater from 12 vertical wells was used to examine the effects of methane and nutrient (nitrogen and phosphorus) dosing on the methanotr ophic populations and on the potential of the subsurface microbial com munities to degrade TCE. Densities of methanotrophs increased 3-5 orde rs of magnitude during the methane- and nutrient-injection phases; thi s increase coincided with the higher methane levels observed in the mo nitoring wells, TCE degradation capacity, although not directly tied t o methane concentration, responded to the methane injection, and respo nded more dramatically to the multiple-nutrient injection. These resul ts support the crucial role of methane, nitrogen, and phosphorus as am ended nutrients in TCE bioremediation. The enhancing effects of nutrie nt dosing on microbial abundance and degradative potentials, coupled w ith increased chloride concentrations, provided multiple lines of evid ence substantiating the effectiveness of this integrated in situ biore mediation process.