TECHNOLOGY AREA(S): Materials
OBJECTIVE: A novel technology that achieves permanent disposal of Aqueous Film-Forming Foam (AFFF) and associated perfluorocarbon components.
DESCRIPTION: AFFF based on perfluorooctyl-substituted surfactants was for decades the water-based firefighting agent of choice in military and civilian applications until it was determined that two highly persistent, bioaccumulative compounds formed from decomposition of AFFF -- perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) -- pose a health risk and display unacceptable toxicity to aquatic index organisms. As a safety measure, Ansuls literature recommends incineration of post-extinguishment wastewaters containing combustible quantities of fuel hydrocarbons; however, it offers no method for disposal of AFFF itself. The Air Force is ridding itself of a large inventory of type 3 MILSPEC AFFF, for which no satisfactory disposal method has been identified, and switching to a shorter-chain homologue for firefighting. A practical method for disposal of AFFF residues and AFFF concentrate will have to manage several significant challenges: - the concentrate is typically supplied as a mixture of water, soluble organics and anionic, amphoteric, and/or non-ionic hydrocarbon surfactants, with a total fluorosurfactant content of 1-10%; - the C“F bonds of PFOS and PFOA, either attached to the surfactant or as the free acid or salt, are extremely stable; - the high-temperature chemistry of PFOS and PFOA has not been characterized, so there is no precedent to predict products of pyrolysis or combustion, temperatures at which these will occur, or the extent of destruction that will be realized; - many likely byproducts will also be environmentally unsatisfactory -- e.g., any volatile perfluoroalkane will be a greenhouse gas -- or toxic, e.g., HF, fluoroacetates, or perfluoroisobutylene. Water effluent from the treatment process may contain no more than 70 parts per trillion (ppt) combined concentration of PFOS and PFOA in any form. Quantities/concentrations of other treatment byproducts released from the treatment process must comply with applicable regulatory standards. Candidate technologies should balance commercial considerations with DoD requirements. Novelty and economics will be factors in the evaluation process. An advanced oxidation process based on oxidation by persulfate is being evaluated by another government agency for groundwater remediation. Related approaches will not be considered for this topic.
PHASE I: The research & development goals of phase I are to identify and validate a chemistry or physics that converts AFFF into environmentally acceptable products, and to demonstrate this process at a treatment rate of 1 gallon/day or more of AFFF. Deliverables include a tech report detailing design, construction, data, interpretation, and a design for a 10-gallon/hour (gph) treatment system.
PHASE II: During Phase II a scalable prototype treatment system will be designed, built, and demonstrated to process 10 gph of AFFF. System will be demonstrated at AFCEC'sFire Research Facilities to deliver an effluent concentration at 10 gphtype 3 MILSPEC AFFFof<70 ppt total PFOS + PFOA.
PHASE III: Design, assemble and demonstrate continuous, full-scale operation of a system -- including a detailed installation/operator guidance/maintenance manual -- to convert 400 gph of type 3 MILSPEC AFFF concentrate into products that can either be reused or disposed as a nonhazardous waste.
1. Ansul, Environmental aspects of AFFF and ar-AFFF, https://www.ansul.com/en/us/DocMedia/F-2003115.pdf
2. D.M. Lemal, Perspective on Fluorocarbon Chemistry, Journal of Organic Chemistry, vol. 69(1):pp. 1-11 (2004).
3. American Wastewater Association, Treatment and Removal of PFCs, www.awwa.org/Portals/0/files/legreg/documents/AWWAPFCFFactSheetTreatmentandRemoval.pdf
KEYWORDS: AFFF, Destruction, Environmental, Fluorocarbon, PFOA, PFOS