Dioxane-Degrading Propanotrophs for In Situ Remediation

Margaret Findlay Ph.D., Donna Smoler, Samuel Fogel, Ph.D (Bioremediation Consulting Inc., Watertown Massachusetts)

Bioremediation Consulting Inc (BCI) has cultured propane-utilizing aerobic bacteria (propano-trophs) from groundwater at several sites. All cultures have the ability to co-metabolically degrade 1,4-dioxane, using the enzyme system designed to oxidize propane. Generally, dioxane and propane ‘compete’ for oxygen, such that dioxane is degraded when the propane dissolved in the water has been nearly depleted. Concentrations of dioxane up to about 10 ppm are readily degraded, but higher concentrations are inhibitory. For in situ bioremediation of dioxane, groundwater would be amended with propane and probably also oxygen. The need for bioaugmentation with Propanotrophs would assessed by microcosm tests using site groundwater.

For complex industrial sites, consideration of additional factors is important. Other contaminants, such as freon, may be non-competitively inhibitory to propanotroph growth. In addition, aerobically-degradable products of contaminant degradation, such as acetate from solvents such as methanol, and even from abiotic TCA breakdown, will compete for oxygen, temporarily inhibiting propanotroph growth. Four cultures will be compared with respect to: