Biotransformations: Persistent organics

Recently, fluorinated organic compounds have been found in wildlife, waters, and humans throughout the world.  Many of these compounds meet the US Environmental Protection Agency’s definition of persistent, bioaccumulative, and toxic pollutants (PBTs). 

Our lab is currently investigating microbial transformations of N-EtFOSE, a fluorinated surfactant used in oil- and water-repellant-coatings, that may help explain the current pattern of fluorinated organic compounds in the environment.  N-EtFOSE is expected to enter landfills and wastewater treatment plants, where microbial transformations may take place.  Potential transformation products of N-EtFOSE include perfluorooctane sulfonate, which has been shown to be toxic at high levels.  Transformation pathways and rates will be determined using batch and continuous reactors under both aerobic and anaerobic conditions.  In addition, we are studying the impact of fluorinated chemicals, such as N-EtFOSE, on microbial community structures of wastewater treatment plants (Slide showing fate of carpet fibers).


N-EtFOSE
(N-ethyl-N-(2-hydroxyethyl) perfluorooctanesulfonamide)

Design of Green Chemicals

Due to the high strength of the carbon-fluorine bond, many fluorinated organic compounds undergo little or no transformation in the environment.  These relatively inert molecules persist in the environment and are difficult to remediate.  Flourinated organic compounds that are toxic and/or accumulate in foodchains present additional human and ecological risks.

By designing fluorinated compounds that degrade in the environment, we hope to promote safer “green chemistry” alternatives to the lubricants, surfactants, and fire-fighting foams used today.  We are evaluating several classes of compounds for transformation under either aerobic or anaerobic conditions to nontoxic products.  The ultimate goal of this project is to determine a set of structural features that can be used to predict the fate of fluorinate organic compounds in the environment.

This project is in collaboration with the Luthy group, which is investigating the physical processes influencing the long-term fate of fluorocarbons and their potential for bioaccumulation in foodchains.

For more information, please contact Kurt Rhoads (krhoads@stanford.edu)