INFLUENCE OF NITROGEN AND PHOSPHORUS ON THE IN-SITU BIOREMEDIATION OFTRICHLOROETHYLENE

The US Department of Energy, Office of Technology Development, has sup ported a field-scale in situ demonstration of trichloroethylene (TCE) bioremediation at the Westinghouse Savannah River Site (WSRS). Several methods were used to examine the influence of nitrogen and phosphorus species on TCE degradation during methane (CH4) injection into contam inated sediments. Laboratory experiments using WSRS ground water revea led that the rate of acetate incorporation into microbial lipids was s timulated when triethyl-phosphate (TEP) or nitrous oxide (N2O) was add ed. The trend was: CH4 + N2O > CH4 + TEP > CH4 + N2O + TEP > CH4 alone . The degree of stimulation of C-14-TCE mineralization in ground water incubated for 30 d in the laboratory with added methane and nutrients increased in the order: OP = TEP > NH3 + TEP = NH3 > N2O (OP, orthoph osphate; NH3, ammonia). Monitoring of WSRS ground water revealed signi ficant differences among sampling wells over time in nutrient concentr ations, nitrogen uptake, and urease activity during operations of the bioremediation demonstration. In the field, the addition of TEP + N2O to the pulsed injection of CH4 resulted in dramatic stimulation of TCE -degrading potentials observed in ground water enrichments. The potent ial to mineralize C-14-TCE in ground water enriched with nutrients in the laboratory increased from <50% of the samples taken during injecti on of methane in the field to >90% of the samples taken during the inj ection of CH4 + TEP + N2O treatment. These results demonstrated the dr amatic impacts of nitrogen and phosphorus supplements during the in si tu bioremediation of chlorinated solvents.