Review of water treatment systems for PFAS removal
The group of perfluoroalkyl and polyfluoroalkyl substances (PFAS) is a large family of anthropogenic substances with a wide range of industrial applications. Due to their specific properties, PFAS are also used as ingredients in many formulations of Class B firefighting foams designed to fight flammable liquid fires. PFAS can and have been released into the environment during firefighting events, testing of firefighting equipment or firefighting training exercises. Due to the persistence, bioaccumulation potential and toxicity of several members of the PFAS family these substances are regarded as environmental contaminants of concern. Several regulations has been recently introduced, which restricts the manufacture and use of PFAS substances, particularly those containing more than six fully fluorinated carbon atoms.
Due to their numerous and widespread uses, mobility and persistence, PFAS are ubiquitous environmental contaminants. They have also been found at oil refinery sites in soils and groundwaters as a consequence of their historic use. As such there is an interest in removing PFAS from fire fighting (also referred to as fireextinguishing) water run-off and groundwater in contaminated areas. This is the second of two Concawe reports on PFAS. The first report (Concawe report no. 8/16) provided and overview of the environmental fate and effects of poly- and perfluoroalkyl substances. This second report critically evaluates technologies and treatment systems for removing PFAS from both fire fighting water and groundwater. Firefighting water is likely to have PFAS concentrations which are two orders of magnitude higher than in groundwater, along with several cocontaminants.
While groundwater may require pre-treatment, for example to remove ferrous iron which can cause clogging issues.
The technologies under consideration can be grouped in four main categories:
1. Adsorption technologies, including activated carbon, resins and novel PFASspecific absorbents;
2. Flocculation technologies;
3. Liquid-liquid separation technologies, including nanofiltration and reverseosmosis, foam fractionation, and distillation; and,
4. Destructive technologies, including electrochemical degradation, sonochemistry, UV radiation, plasma destruction and water incineration.
A brief description of each technology is provided, followed by an evaluation of their suitability to remove different PFAS from either firefighting water or groundwater. The evaluation of both types of water was undertaken because some technologies may only be suitable for specific PFAS concentration ranges which may preclude their use depending on the type of water to be addressed. When available each evaluation is supported with technology case studies which are summarised in the Appendix to this report.
The results of the evaluation towards different criteria are summarized in lookup tables for groundwater treatment and fire-extinguishing water treatment, respectively, allowing an informed selection of the most suitable technology for a given scenario.