Elimination of PFAS/PFOS/PFOA

SCWO technology eliminates 99,9% of PFAS from wastewater

Aquarden Technologies has made a number of tests with removal of per- and polyfluoroalkyl substances (PFAS) from leachate and problematic wastewater with great success. The PFAS group of chemicals includes substances such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) that have been identified with growing concern as highly carcinogenic contaminants.

An initial study with leachate from Sörab waste deposit (SE) containing PFAS documented a successful removal of 19 PFAS/PFOS/PFOA components from the raw leachate.

After treatment in our SCWO reactor, all 19 PFAS substances including PFOS and PFOA were measured and found to be 99,9% eliminated. Results are shown in the figure below:

PFOS elimination

These compounds are extremely difficult to degrade even with advanced oxidation technologies but SCWO is able to completely destroy them.

PFAS

Widely spread

Large quantities of groundwater and soil are presently contaminated with PFAS that are found to be persistent, bioaccumulative and toxic. PFAS have been applied in many products and especially as flame retardants, and are extremely recalcitrant to conventional remediation technologies such as chemical and biological degradation. Therefore, the most common solution is to adsorb PFAS on activated carbon. The spent carbon typically needs to be transported great distances for treatment in special incineration plants that operate at extremely high temperatures for destroying the PFAS. This is a costly solution with a high carbon footprint.

Onsite treatment

Aquarden now offers an effective, onsite treatment of PFAS contaminated wastewaters with SCWO.  Wastewater at high pressure and temperature is mixed with oxygen in the SCWO reactor, and results in a rapid and complete oxidation of all organic micro-pollutants, whereby pollutants are typically eliminated below their detection limits.

Progressing

In addition, Aquarden is developing a process to wash PFAS off spent carbon and produce a PFAS-concentrate for treatment with SCWO. This process essentially concentrates PFAS from the raw wastewater into a much smaller volume of water for SCWO treatment, which in turn greatly lowers operational costs. Furthermore, the washed carbon can be reused for adsorption.  Aquarden is also investigating using membranes or PFAS-specific adsorbents for capturing and concentrating PFAS.

Removal of PFAS from a Swedish airfield

Fire drills are conducted regularly on airfields, where fire extinguishing agents containing PFAS are used. As on many airfields, one airfield in Sweden has identified PFAS as a pollutant in their soil and water, and has therefore engaged Aquarden Technologies to remove these compounds.

Case about PFOS

Aquarden’s patented SCWO system has proven complete destruction of PFOS in groundwater below detection limits, where PFOS is fully broken down into harmless compounds such as water, nitrogen, and carbon dioxide.

In short, this is what we do with PFAS-contaminated water:

  1. PFAS is adsorbed to activated carbon.
  2. Activated carbon is then “washed” for a period of time with a methanol/ethanol solution to produce a PFAS-concentrate.
  3. The PFAS-concentrate is subsequently treated in the SCWO plant.

Both results can be seen in the scheme:

PFOS ug/L PFOA ug/L
PFAS-concentrate from airfield 679 34
 Water after SCWO treatment <0.1 <0.01