Document Type thesis Author Name Bourgeois, Amy Laura Liu Email Address bourgeois.amy at gmail.com URN etd-042914-221927 Title Biodegradability of Fluorination Fire Fighting Foams Degree MS Department Civil & Environmental Engineering Advisors John Bergendahl, Advisor Ali Rangwala, Co-Advisor Paul Mathisen, Committee Member Keywords fire fighting foams biodegradability AFFF Date of Presentation/Defense 2014-04-29 Availability unrestricted
Fluorinated fire fighting foams provide superior performance for extinguishing Class B flammable liquid fires when compared to other types of fire fighting foams. Perfluorocarboxylates and perfluorosulfonates have historically been surfactants used in these foams with a recent shift to fluorotelomer-based foams due to environmental and health concerns surrounding perfluorinated compounds such as PFOA and PFOS. Releases of aqueous film forming foams from training, accidental spills, or fire events where wastewater is not captured have, among other sources, led to detectable concentrations of fluorinated compounds in groundwater, surface water, and drinking water supplies globally. Persistence, toxicity, and bioaccumulation potential of these substances are areas of ongoing research.
Biodegradability data for these AFFFs in published studies and manufacturers’ material safety data sheets may be based on a comparison of BOD and COD measures. The present study concludes that COD is an inappropriate measure of organic content for fluorinated compounds due to the carbon-fluorine bond strength, and thus published biodegradability data must be critically evaluated for validity. TOC measured an average of 91% of carbon content for four fluorinated test substances, recommending it for use as an analytical parameter in biodegradability tests when specific compounds’ identities are not required, e.g. in the absence of an LC/MS.
Biodegradability of three fluorinated foams (AFFF, AR-AFFF, and FP) purchased from a major U.S. manufacturer measured in the range of 77-96% based on DOC die-away during a 28-day test using activated sludge inoculum. This meets OECD criteria for “ready biodegradability” and NFPA biodegradability recommendations in Standards 18, 18A, and 1150. Defluorination of two foams was measured using ion chromatography and, based on an estimate for total fluorine content developed in part from manufacturer MSDSs, was found to liberate a detectable level of fluorine that was 1 to 2 orders of magnitude less than the estimated value. In this 28-day test, foams underwent significant biodegradation but fluorinated compounds’ biodegradation was likely incomplete.
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