The WDNR has launched a statewide initiative to mitigate PFAS in our drinking water. What does this mean for your municipal wastewater treatment facility?
The PFAS Problem
Per- and poly-fluoroalkyl substances (PFAS) are a group of synthetic fluorinated compounds used in a wide variety of consumer goods for more than 50 years in the late 20th century. PFAS vary in structure, electric charge, and length, but each member of the PFAS family is comprised of a highly fluorinated alkyl chain. The fluorine-carbon bonds of PFAS prove to be nearly indestructible.
Originally used as firefighting foams, PFAS have been used as stain repellents, anti-stick coatings, and surfactants. Despite their useful chemical properties, PFAS are no longer manufactured, other than for some firefighting foams, due to their classification as a persistent organic pollutant. Today they are found in groundwater, surface water, and soils. They bioaccumulate in tissues, negatively impacting human and animal health, and have been linked as cancer-causing on the order of nanograms per liter (parts per trillion). Over 4,000 different PFAS are known, many of which are detected in humans and wildlife. PFAS are naturally prone to attach to solids and other particles via sorption. Concerns have grown over the years as PFAS contamination has been discovered in municipal and private wells.
PFAS Regulation
Because of their adverse effects on humans and the environment, various governing agencies have started regulating PFAS. However, laboratory testing methods and standards are still being developed for PFAS, complicating the path to effective regulation.
The United States federal government has set an advisory limit on the concentrations of two forms of PFAS, PFOA and PFOS, for surface and groundwater levels at 70 parts per trillion. Concentrations above this level are likely to be harmful to human health if ingested.
The Wisconsin Department of Natural Resources (WDNR) is actively working towards regulating PFAS in the water and wastewater arenas. However, because the label ‘PFAS’ represents thousands of different chemicals, regulation is complicated.
One approach is to regulate the most common compounds by setting a maximum contaminant level (MCL). These limits would likely be in parts per trillion. While this could be effective, the implications of regulating PFAS in clear water and/or biosolids are vast, and scientists do not yet fully understand the impact of PFAS contamination.
Alternatively, regulatory agencies may develop an MCL for total PFAS instead of specific compounds.
PFAS Treatment and WWTFs
Because of the extreme resilience of the PFAS carbon-fluorine bonds, removal is more realistic than destruction when treating PFAS contamination. Carbon adsorption and ion exchange, among other treatment technologies, can remove PFAS from water at a significant cost. Research into the best methods for destroying PFAS (including electrochemical oxidation and boron nitride treatment) is just beginning.
PFAS are thought to pass through traditional activated sludge treatment processes offered at most wastewater treatment facilities (WWTFs). PFAS may accumulate in biosolids due to their resistance to destruction and affinity for sorption. PFAS can enter WWTFs through contaminated municipal and industrial waste, or via sanitary sewer inflow and infiltration of water through contaminated soils. If any PFAS enter a WWTF, it is likely that they will end up sorbed to the biosolids or sorbed to constituents in the effluent.
Partitioning of PFAS to biosolids is complicated and depends on the PFAS characteristics, concentration, solution chemistry, and biosolids digestion process. The Water Research Foundation has several studies in the initial phases to better understand the partitioning process.
Other concerns for WWTFs include how PFAS may affect treatment of conventional wastewater pollutants such as carbonaceous biochemical demand, total suspended solids, ammonia-nitrogen, and total phosphorus.
It’s unclear if WWTFs will be expected to remove PFAS in addition to natural partitioning to biosolids, with a specific treatment method. Any additional PFAS removal would be extremely expensive, which is why studies are focused on reducing PFAS usage from initial sources such as in firefighting and consumer products.
LEARN MORE
The full impact of PFAS regulation and mitigation within your WWTF is still unknown. Our team is closely monitoring updates as they are made available. In the meantime, if you have questions or concerns regarding PFAS regulations, please contact us today.
