Formatted Title
Foam Fractionation Case Studies and Assessment of Operational Gas and Configuration to Optimize PFAS Removal Efficiency
Background/Objectives
Landfills and sewage treatment plants (STP) have been identified as long-term sources of per- and poly-fluoroalkyl acid substances (PFAS) entering the environment either in low concentrations via their routine authorised discharges or with varying concentrations within accidental releases. Both these end-points pose significate challenges to the majority of acknowledged PFAS water treatment technologies, due to their high concentrations of organics (biological and chemical), nutrients, inorganics and often comparatively low concentrations of problematic contaminants including PFAS.
Since 2017, when Arcadis teamed up with Evocra to successfully install and operate the world’s first commercial scale foam fractionation system to remove PFAS from impacted waters resulting from an accidental discharge of firefighting foam, foam fractionation has emerged as a viable technology for removing PFAS from many water sources. In Australia, Arcadis and Evocra have applied the foam fractionation to both domestic wastewater and landfill leachate, in addition to groundwater, surface waters and fire training ground run-off, successfully removing PFAS to meet strict criteria defined by total oxidizable precursor (TOP) assay. On the global stage, Arcadis and a growing number of other commercial operators have demonstrated the technologies application to landfill leachate on numerous sites.
Approach/Activities
Although all the various foam fractionation operators agree the technology provides effective PFAS removal as a standalone operation or as part of a treatment train, there is a misunderstanding of the benefits of using ozone as the working gas. A number of recent commercial-scale applications, pilot trials, lab trials and third-party research studies comparing ozone and air foam fractionation have demonstrated benefits and opportunities for improvement for both variants as well as providing conflicting results (V Phong et al., 2024).
- During a 2021 pilot-scale study on landfill leachate using a three column continuous flow foam fractionation system Arcadis-Evocra evaluated that ozone-only and an air-ozone combination provided greater removal efficiency of both long- and short-chain PFAS, with lower fractionate (waste) generation than the air-only system. This work also identified that the air-only system was oxidizing precursor PFAS, which had previously been assumed to only occur when using ozone.
- Work carried out in late 2022 by the University of Queensland (UQ), Australia with a bench-scale batch fractionation column, again processing landfill leachate, identified that using ozone-only in the system reduced fractionate production by 200% to 400%, from that observed in the air-only system. Since waste disposal of fractionate is a significant cost driver in the operation of foam fractionation systems, reducing fractionate production while maximizing PFAS removal is a critical consideration that will be assessed and presented.
- This same UQ study also shows a marginally higher PFAS removal efficiency for the air-only system compared to operating the ozone-only system.
The presentation seeks to openly assess working gas performance as well as processing modes, continuous versus batch, with the aim to further improve the understanding of foam fractionation. The improved knowledge can assist practitioners and patrons to evaluate the likely performance of foam fractionation systems in relation to PFAS removal from complex water systems, allowing them to select the appropriate treatment process to meet the specific site requirements and constraints.
Results/Lessons Learned
During the presentation, case study data from the forementioned studies along with data from earlier projects and projects currently in start-up phases will be provided, to assist the optimisation evaluation of foam fractionation systems. Presented data will include:
- Removal efficiency by treatment stage for key PFAS analytes;
- Waste fractionate generation as a fraction of treated volume; and
- Key operational parameters for maximizing PFAS removal and minimising fractionate generation.