Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7d. Ex Situ PFAS Water Treatment Technologies

Formatted Title:

Treatment of PFAS-Contaminated Soil Wash Water Using SAFF and Destruction for Closed Loop Water Treatment Option

Background/Objectives:

OPEC Enviro, an Australian environmental engineering company, and Envytech have developed a PFAS separation and concentration process based entirely on the surface active power of rising air bubbles in a water column. This PFAS treatment method, named SAFF, removes PFAS6 up to 99,9% using no consumables or additives, producing minimal waste. The PFAS6, due to their surface active properties, are the predominant PFAS found in weathered soil in hot spot areas; the SAFF was believed to be an effective treatment method for soil wash process water, and this has been proven in a full-scale application of SAFF as the only treatment method for soil wash process water at a permanent soil washing installation in Belgium. The project started in March 2023 and has to date treated over 150 000 m³ of soil wash process water from numerous different soils with different origins and PFAS concentrations. The SAFF incorporates a unique waste minimization process, producing only small concentrations of PFAS concentrate as waste. To evaluate if a closed loop system could be achieved for the water treatment, destruction of the PFAS concentrate using several destruction technologies have been trialed and evaluated in regards of energy use, cost per m³ waste treated and possibility for full-scale application.

Approach/Activities:

The soil wash plant in Belgium is operated by the company Carmans B.V, and is a full-scale, permanent, commercial soil wash plant treating different kinds of soils and contaminants. As the company wanted to start performing soil wash of PFAS-contaminated soil, Envytech Solutions AB supplied a SAFF as the only treatment step for PFAS, by installing the SAFF as a last treatment step in the already existing water treatment system made up from flocculation and precipitation followed by sand filters for removal of suspended solids. The SAFF system, in combination with the already existing pre-treatment system for solids, treats the incoming process water before returning it to the soil wash process in a closed loop. The untreated, as well as the treated process water, is sampled regularly in regards of 20 PFAS to continuously monitor the performance of the system. The minimal waste produced has been stored on site, as the client is looking for an effective and economic solution. Envytech have together with several different destruction technologies performed bench-scale destruction trials for the concentrate, to evaluate efficiency, cost and possible full-scale alternatives available on the commercial market.

Results/Lessons Learned:

The performance of the SAFF shown by continuously sampling and analysis of 20 PFAS shows high efficiency of the SAFF for treating the dominant PFAS in the soil wash process water, containing PFAS from many different soils of different origin, types and concentrations. Results show removal rates with up to 99.9% for the predominant PFAS, and the solution has been proven to provide sufficient capacity to work as a stand-alone, full-scale treatment solution for PFAS, using no consumables, only electricity and air, while needing very limited amount of service performed by regular treatment plant staff only. The small amounts of PFAS concentrate that make up the waste has been proven to be suitable for destruction by several commercially available destruction technologies. Results will be presented as treatment efficiency for PFAS, cost of treatment including service per treated ton of PFAS contaminated soil and m³ treated process water, as well as efficiency and cost of destruction technologies to provide a closed loop system, generating no waste from the water treatment process.

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Robin Axelson