Performance of water treatment systems for PFAS removal
Report no. 5/21: Per- and polyfluoroalkyl substances (PFAS) are a group of widely used man-made organic chemical substances. They contain alkyl groups on which all or many of the hydrogen atoms have been replaced with fluorine. As such, they contain at least one perfluoroalkyl moiety, –(CF2)n–. PFAS have been used because of their particular physicochemical properties: most are stable at high temperatures, recalcitrant to chemical oxidation and biological degradation (i.e., persistent), and act as a surfactant. Although beyond the scope of this report, as reported by the Australian Ministry of Defense6, among others these properties mean there are a wide variety of PFAS-containing materials (e.g stain- resistant fabrics, nonstick cookware, polishes, personal care products, and fire-fighting foams), or materials where PFAS is used in the process (e.g. Mist suppression in metal plating or photography). Many such substances may also be bio-accumulative and toxic. In this study several treatment technologies for PFAS removal were tested in the laboratory on both groundwater containing PFAS, and firefighting wastewater obtained from a firefighting training site where firefighting foam was applied. The treatment technologies assessed were performance of sorbents, coagulation/flocculation, nanofiltration, foam- and ozo fractionation technologies. In all cases the PFAS removal effectiveness was evaluated. This report provides:
- Criteria and background information to select potential treatment technologies.
- Results of these performance tests of water treatment technologies for PFAS removal.
- Practicalities such as availability of the technology and experimental feasibility which are included in the evaluation.
- Recommendations for selection of treatment technologies for PFAS removal in practice for impacted groundwater and firefighting wastewater.
Experiments showed that all tested sorbents were able to remove PFAS from firefighting wastewater but the required sorbent dosages were in the g/L range. It is therefore concluded that groundwater containing PFAS can be treated with one of the tested sorbents directly, while for firefighting wastewater, which typically has higher PFAS concentrations as well as other contaminants, a treatment train approach is likely to be more efficient. An initial treatment, such as flocculation, nanofiltration or foam- / ozo fractionation that removes bulk PFAS load including co-contaminants followed by a polishing treatment (e.g. sorbents) that further reduces PFAS concentrations to acceptable levels is advised, unless a relative small fixed volume of firefighting wastewater needs to be treated. This study provides a basis for readers of this publication to select, study and apply the best available technologies to mitigate risks associated with PFAS contamination.