Grantee Research Project Results
Biodegradation of Perfluorinated Organic Compounds
EPA Grant Number: F5A20157Title: Biodegradation of Perfluorinated Organic Compounds
Investigators: Rhoads, Kurt R.
Institution: Stanford University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through August 1, 2008
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
Objective:
Recently, perfluoronated bioaccumulative and toxic chemicals such as perfluorooctanesulfonate (PFOS) have been found in fish, birds, marine mammals, and humans. Suspected sources of PFOS include perfluoroalkyl chemicals (PFACs), used as surface treatments for carpets, upholstery, paper, and cardboard. Initial results suggest that microbes present in wastewater sludge have the capability to transform model PFACs to products including PFOS. The objectives of this project are to:
- determine the likely biotransformation pathways and endproducts of PFACs under both aerobic and anaerobic conditions;
- estimate biotransformation rates in wastewater treatment plants;
- and determine if altering the microbial community within a reactor can increase biotransformation rates.
Approach:
Batch studies will be performed using both aerobic activated sludge and anaerobic digester sludge to determine biotransformation pathways of PFACs and initial kinetic parameters. Additional kinetic studies will be performed using continuously stirred reactors with cell retention (porous pot reactors) to approximate activated sludge treatment. In an attempt to shift microbial community structure towards increased PFAC degradation rates, actively-degrading cultures will be successively transferred to new medium containing PFACs. Microbial communities will be assessed using terminal restriction length fragment polymorphism (T-RFLP).
Expected Results:
The results of this study will indicate key biotransformation products of PFACs, including some those that are bioaccumulative and/or toxic. In addition, kinetic parameters determined in this study will allow for prediction of biotransformation rates. Together, these two sets of information will help explain the global distribution of PFACs and their transformation products. Finally, the alteration of microbial communities within treatment plants may allow for enhanced transformation of PFACs.