“This is the first time we have shown which floating wetland plants that can purify water from PFAS,” says Maria Greger, associate professor in plant physiology at Stockholm University. For thirty years, she has led research on the subject of phytoremediation, in which plants are used to clean soil, water and air from pollution.

PFAS is a collective name for persistent highly fluorinated substances e.g. used in fire foam, as impregnation agents and in Teflon pans. To purify water from PFAS, a method with active carbon is currently used. But this purification method is expensive and is therefore only used in water treatment plants for drinking water. Floating wetland plants, where cultivation methodology and choice of plants are crucial, make purification of PFAS possible even in natural water.

The study was conducted on fresh water from the lake Sänksjön in Kallinge in Blekinge, Sweden. Adjacent to this lake is the F17 air wing, where the armed forces have used fire foam containing PFAS in their fire drills. PFAS levels are remarkably high in this water, as well as in several watercourses connected to fire training sites and airfields.

“We observed that all PFAS substances decreased significantly over time by up to 40 percent over a 24-hour period. The size of the plant biomass was found to be more important for effective purification than a specific plant species,” says Maria Greger.  

Sedges are among the species that most rapidly reduced the concentration of heavy metals. The plants take up PFAS and accumulate it in the shoots, which can be harvested, making it easy to remove the contamination from the site. The researchers have also shown that the plant degrade PFAS in the water with the help of the plant enzymes and the degradation products are also taken up by the plant.

Reducing the levels of PFAS in the water of water sources with floating wetland plants can eventually also reduce PFAS levels in drinking water.

“A floating wetland with wetland plants is an inexpensive method that could be used in watercourses where the water is contaminated with PFAS. The method could also be developed for use on one's own property if the water there has been contaminated with PFAS,” says Maria Greger.