PFAS:
Definition & Overview
What is PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a group of over 6,500 synthetic chemicals characterized by their strong carbon-fluorine bonds. These chemicals have been manufactured and used since the 1940s due to their unique properties, including resistance to heat, water, and oil.
What are the health risks associated with PFAS exposure?
PFAS are considered "forever chemicals" because they persist in the environment and do not break down easily. This persistence, coupled with their ability to bioaccumulate in living organisms, raises concerns about their potential impact on human health.
The two most studied and commonly detected PFAS in the environment are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). In 2022, the Environmental Protection Agency (EPA) established health advisory levels of 0.004 parts per trillion (ppt) for PFOA and 0.02 ppt for PFOS in drinking water. Exposure to PFOA and PFOS have been linked to various health issues, including:
Developmental and reproductive problems
Decreased immune function
Increased risk of cancer
Decreased fertility
Negative effects on the developing fetus
Increased risk of high cholesterol
Liver damage
Decreased vaccine response in children
Disruption of thyroid hormone regulation
Adverse pregnancy outcomes
Developmental effects in infants and children, such as ADHD
Addressing PFAS in wastewater treatment plants is essential for protecting public health and the environment.
What products use PFAS?
Numerous products and industries use PFAS due to their unique properties. Some common products containing PFAS include:
Non-stick cookware (e.g., Teflon)
Stain-resistant carpets and fabrics (e.g., Scotchgard)
Water-repellent clothing and outdoor gear
Food packaging materials, such as microwave popcorn bags and fast-food wrappers
Firefighting foams, especially aqueous film-forming foams (AFFF) used at airports and military bases
Industrial processes that contain PFAS include:
· Metal plating
· Paper production
· Electronics manufacturing
Companies that have been associated with the use of PFAS in their products include 3M, DuPont, Chemours, and Gore-Tex.
Some companies have voluntarily phased out the production of certain PFAS (like 3M, which will phase out PFAS by the end of 2025), such as PFOA and PFOS, due to increasing concerns about their environmental and health impacts.
How does PFAS end up in wastewater treatment plants?
PFAS can enter wastewater treatment plants (WWTPs) through various sources, including industrial discharges, residential wastewater, and stormwater runoff. PFAS-containing firefighting foams, as well as consumer products such as non-stick cookware, water-resistant clothing, and food packaging materials, can contribute to PFAS presence in wastewater.
How to manage PFAS in sludge and biosolids?
Traditional wastewater treatment processes, such as activated sludge and primary clarification, are generally ineffective at removing PFAS from contaminated wastewater. Even after dewatering, sludge often still contains PFAS.
As PFAS regulations become more stringent, wastewater treatment plants face new challenges in disposing of PFAS-contaminated sludge and biosolids.
Strict limits on PFAS concentrations in biosolids for land application lead to fewer disposal options, increased costs, and logistical challenges. For example, the reduced demand for biosolids as fertilizers due to contamination concerns complicates disposal and management efforts.
Landfill Disposal
PFAS-contaminated biosolids above regulatory limits are typically disposed of in Subtitle C or RCRA-permitted landfills, which are specifically designed to manage hazardous wastes.
As PFAS regulations tighten at both federal and state levels, landfills must implement additional measures, such as containment and liner installation, leachate management and collection systems, monitoring, closure, and post-closure care, to comply with regulations and prevent PFAS contamination.
These measures increase the cost of landfill disposal, which are often passed on to wastewater treatment plants. Additionally, stricter regulations limit the number of landfills that can accept PFAS-contaminated biosolids, leading to higher transportation costs and a more competitive disposal market.
To cut disposal costs, wastewater treatment plants are exploring various strategies.
One strategy is to further dehydrate dewatered sludge. Drying sludge cake beyond what centrifuges and mechanical presses (eg. belt press, screw press) are capable of reduces the weight and volume of the waste WWTPs send to landfills, decreasing overall disposal costs. Additionally, drier cake is less likely to produce leachate given its lower water content.
The Electro Osmosis Dehydrator is an efficient, non-thermal dryer that pairs with existing dewatering machines to further dewater sludge cake weight by 50%+ and help WWTPs save on their disposal costs.
High Temperature PFAS Destruction
Another strategy is to use high temperature processes to destroy PFAS in sludge cake. High-temperature processes, including incineration, pyrolysis, gasification, and thermal oxidation, can destroy PFAS in sludge and biosolids, but require substantial energy input and generate emissions that need careful control and monitoring.
These high temperature processes can achieve better performance and efficiency by maximizing the dryness of the sludge cake being fed into them. Sludge dryers like the Electro Osmosis Dehydrator and high-temperature systems like Incinerators should be utilized in a complementary fashion to manage PFAS efficiently and effectively.
Drying sludge prior to these high-temperature processes minimizes the energy required for heating and evaporating water, thereby optimizing treatment efficiency. By drying sludge first, high temperature processes can focus on destroying PFAS and other contaminants, as less energy is required to evaporate water.
Dewater sludge with ELODE
Our ELODE non-thermal sludge dryer further dewaters sludge cakes produced by mechanical sludge dewatering equipment. Compared to thermal dryers, ELODE is more cost-effective, energy-efficient, and has a small footprint.
Save on operating costs by reducing your sludge cake by 50% or more in just 3 minutes with ELODE.