<p>EFFECTS OF SUBSTRATE CONCENTRATION ON PERMEABILITY REDUCTION AND TCE DEGRADATION IN A MULTI-SPECIES BIOFILM</p><p>1John Komlos, 1Al Cunningham, and 2Robert Sharp</p><p>1Center for Biofilm Engineering, Montana State University, 366 EPS Building, Bozeman, MT 59717-3980; 2Environmental Engineering Department, Leo Hall, Manhattan College, Riverdale, NY 10471; 1Phone: (406) 994-4770; 2Phone: (718) 862-7169.</p><p>Recalcitrant compounds, such as trichloroethylene (TCE), show little natural attenuation. The development of a biologically produced subsurface barrier capable of degrading TCE while reducing its migration could result in a significant advancement in bioaugmentation technology. Burkholderia cepacia PR1-pTOM31c has the ability to aerobically degrade TCE but is unable to form a biofilm capable of significantly reducing porous media permeability. This research examined the effects of combining B. cepacia with Klebsiella oxytoca, a thick biofilm-producing bacteria, in order to create a reactive/reduced-permeability biobarrier. The research indicated that species growth rate was not an adequate predictor of which microorganism would out-compete the other in a biofilm. Rather, substrate concentration was a dominant variable in controlling the population distribution of the two organisms. At high substrate concentrations, K. oxytoca was the dominant organism in a dual-species biofilm. At lower substrate concentrations, there was a shift in the population distribution with B. cepacia being the dominant microorganism. Varying substrate concentration enabled us to manipulate the population distribution in this dual-species biofilm. This concept was expanded to a constant head, porous media reactor. The results from the porous media reactor showed a similar shift in population with change in substrate concentration. K. oxytoca provided similar permeability reduction at high and low substrate concentrations. B. cepacia achieved greater population density, and higher TCE-degrading potential, at the lower substrate level. Thus, similar reduction in hydraulic conductivity coupled with a significantly higher TCE-degrading potential at the lower substrate level was observed.</p><p>Key words: biofilm, biobarrier, multi-species, subsurface, trichloroethylene</p>