The overall technical objective of this effort is to demonstrate removal of per- and polyfluoroalkyl substances (PFAS) from bilge and oil wastewater (BOW) to low-level treatment targets as a pre-treatment step that could be applied to conventional bilge and oily wastewater treatment systems (BOWTS), which currently do not have the capability to treat PFAS. Specific objectives include the following:

• Develop and implement a technical approach to remove PFAS from the oily phase in BOW.
• Demonstrate treatment efficacy for the water phase in BOW for PFAS, total suspended solids (TSS), and residual emulsified oil, with foam fractionation while minimizing waste generation.
• Optimize foam fractionation operational parameters to achieve maximal removal efficacy of target constituents during a field demonstration with a pilot-scale, continuous-flow foam fractionation unit.
• Demonstrate a media loading approach for foamate generated in the pilot to further minimize waste that must leave site.

Multiple technical components will be used to treat the BOW. An oil-water separator will be used to physically separate the oil phase present in the BOW. These units operate via oil agglomeration and separation from the aqueous phase. In PFAS-impacted BOW, the generated nonaqueous phase liquid (NAPL) is anticipated to retain a significant proportion of the PFAS mass. Separated NAPL will be stripped of PFAS using liquid-liquid extraction, wherein a NAPL-insoluble extractant (such as methanol or ethanol) is introduced to remove PFAS from the NAPL. After separation of the liquid layers, this stage will result in a PFAS-containing extract that may be treated as a waste product or subjected to further treatment, resulting in a treated NAPL with de minimis PFAS that may be potentially considered for reuse.

Foam fractionation, a separation process capable of concentrating amphiphilic species via introduction of high flow rates of small gas bubbles into a liquid, will be used to treat the aqueous phase of the BOW. The concentrated foam, which will be enriched with TSS and PFAS, is collected and condensed (called foamate) for disposal or further treatment. Foam fractionation is highly attractive as a treatment method for waters like BOW that contain high levels of co-occurring species such as chloride, organics, and solids that interfere with traditional media-based treatments. Two possible foamate concentration steps will be investigated for their relative efficacy and to help determine options for final fate of PFAS-bearing waste streams.

Further liquid concentration, using a specially designed FOAM-X Concentrator, will be used to investigate volume reduction of foamate waste by re-fractionating the foamate. This approach may allow for an additional order of magnitude reduction in liquid waste volume and is often paired with PFAS destruction technologies. SuperLoading™ will also be evaluated for foamate volume waste reduction; it utilizes media beds with extremely long contact times to encourage PFAS sorption onto the media. The typical fate of spent SuperLoader media is solid waste disposal. 

This project will extend the range of the existing BOWTS technology by enabling treatment of several constituents that are commonly found in BOW. This effort will enable the continued use of existing oil pollution abatement systems or BOWTS infrastructure and potentially enable reuse of the separated oil phase after PFAS has been removed. The unique characteristics of this wastewater including the significant portion of NAPL, presence of nano and microemulsions, and capacity to retain PFAS in the NAPL, present a challenge for water treatment providers. Complex water chemistry containing seawater, lubricant hydraulic oils, cleaning agents, biocides, and their dissolved phase byproducts, and TSS largely prevent the simple but expensive default solution of treating PFAS using adsorbent media. The foci for the technical benefit and key innovation of this effort, largely rests with the unique water chemistry of BOW and the form factor and operational regime of foam fractionation. Pilot-scale demonstration on this unique influent is also needed for accurate cost evaluation and comparison to alternative technologies. The technology package is expected to be a best-in-class solution in terms of both cost and resiliency. The successful execution of this demonstration will provide a new technology for treating BOW, ultimately protecting the warfighter and installation communities. (Anticipated Project Completion - 2026)