Removing PFAS: Understanding the Wastewater Treatment Process


*This post was originally published as a part of the Pumps & Systems website.

Per- and polyfluoroalkyl substances (PFAS) have made headlines across the country during the summer of 2023. This group of dangerous and highly persistent chemicals has risen to household name status, as communities throughout the United States grapple with the knowledge of widespread water pollution as well as the daunting cost of treating water to remove the contaminants for years to come.

Now that each of the two largest PFAS manufacturers has proposed its own settlement with U.S. public drinking water systems, the focus is beginning to shift toward PFAS wastewater contamination. Driven by their responsibility to provide a healthy environment for their communities, a desire to maintain positive public opinion, and a need to meet potential new Clean Water Act (CWA) EPA requirements, many municipalities are exploring treatment solutions and cost management strategies for PFAS removal. Wastewater systems that suspect PFAS concentrations in effluent or biosolids should pay close attention to the latest trends in PFAS wastewater management and plan ahead for potential upcoming regulations.

Since effective PFAS treatment methods are the result of relatively recent advances in engineering, municipal leaders may not yet be familiar with the options available, and their associated costs to local utilities and ratepayers. In this blog, we will describe the traditional wastewater treatment process as well as the additional steps that may be incorporated to remove PFAS.

PFAS in Wastewater: A New Challenge for Municipalities

Many wastewater treatment plants (WWTPs) have discovered PFAS in effluent and biosolids. The ubiquity of PFAS in both industrial and household uses means that high concentrations of these contaminants are often present in wastewater as it enters treatment plants.

Wastewater systems are neither producers nor users of PFAS. Nevertheless, they are “receivers” of these chemicals as contaminated wastewater flows into treatment plants from manufacturing facilities, local households, and other sources. Although PFAS in wastewater is the result of upstream producers, the burden of removing the contaminants is likely to fall upon wastewater systems, especially if potential upcoming federal regulations restrict the concentrations of PFAS compounds allowed in wastewater effluent and biosolids.  The EPA has already begun taking steps to designate two PFAS compounds, PFOS and PFOA, as hazardous materials under CERCLA. If these proposed regulations are finalized, WWTPs nationwide may need to significantly expand their facilities to meet the new requirements.

Even as many states are creating limits on PFAS in products manufactured and distributed within their borders, these chemicals’ resistance to biodegradation means that background levels of PFAS resulting from decades of manufacturing and daily use will likely persist. The compounds will continue to be present in wastewater at detectable levels for many years, presenting an ongoing challenge for wastewater systems.

Risks of PFAS Wastewater Contamination

PFAS concentrations in wastewater present several serious risks to municipalities and local residents. Decision makers for local governments and utilities should be aware of the effects that wastewater contamination can have on public health, public opinion, and regulatory compliance.

Public Health Concerns

Associations have been shown between exposure to PFAS and many negative health effects including birth defects, kidney cancer, testicular cancer, thyroid disease, high cholesterol, ulcerative colitis, and preeclampsia. While the primary focus has so far been on PFAS exposure through drinking water, consumer products, firefighting foam and gear, and other industry-related hazards, environmental contamination can also result in serious risks to local residents.

PFAS in wastewater effluent can contaminate local surface water and infiltrate soil and groundwater. As the chemicals spread throughout the environment, they can even make their way into drinking water supplies nearby as well as in downstream communities. PFAS-containing biosolids can also contaminate the soil where they are applied. The compounds have been shown to accumulate in crops where contaminated biosolids have been used as fertilizer. Because PFAS chemicals are highly biopersistent, once they become present in the environment, they are extremely difficult to remove.

Increased Public Scrutiny

Over the past several years, the general public has steadily gained awareness of the dangers of PFAS in the environment. This has resulted in a strong public demand for treatment and remediation to mitigate the risk to their health.

One 2022 study revealed a massive 670% increase in PFAS-related social media posts over two years, indicating rapid growth in users’ interest in and awareness of the chemicals. Posts identified in the study addressed the discovery of contamination events, media coverage, and scientific publications. These results demonstrated that the public perceive PFAS as an immediate public health concern and that they are seeking swift action and transparency from municipalities and other authorities.

Potential for EPA Regulation

As previously mentioned, the EPA has taken steps to classify two PFAS compounds, PFOS and PFOA, as hazardous substances under CERCLA. If this change is finalized, stricter regulations can be expected in the near future. As a result, no detectible level of PFOS and PFOA in wastewater discharge would technically be legal without proper exemptions.

In order to maintain compliance with these potential new regulations, WWTPs across the United States would be required to implement significant treatment plant upgrades to remove PFAS contaminants. In addition, ongoing operational and staffing costs, as well as stricter requirements for continued testing and monitoring of contaminant levels, will likely result in significant cost increases. For many municipalities, these costs will present a difficult burden for utilities and ratepayers to bear.

Below, we describe the general wastewater treatment process used by most WWTPs in the United States, followed by a list of treatment methods gaining popularity for PFAS removal.

Understanding the Wastewater Treatment Process

Since the CWA was passed in 1972, municipalities, districts, and industries have widely adopted biological wastewater treatment to minimize wastewater's environmental impact. While the methods and names of the technologies have changed over time, the process remains similar.

The typical steps taken by WWTPs to make wastewater effluent safe for discharge into the environment fall under four main categories: physical treatment, chemical treatment, biological treatment, and sludge treatment. These four treatment types integrate and work together in order to operate a system to meet compliance.

  • Physical treatment focuses on separating solid materials from wastewater, including large solids, grit, and organics. Techniques for physical treatment include skimming, sedimentation, and screening.
  • Chemical treatment ensures the efficient removal of organic matter and disinfection of wastewater to eliminate harmful pathogens. To achieve this, treatment professionals use methods of coagulation, chlorine disinfection, and pH regulation. Chemical treatment is used during the clarifier, aeration basin, and disinfection steps below.
  • Biological treatment occurs when bacteria cultures feed on wastewater's organics, removing them from the water. Biological treatment is key in breaking down organic matter, including nitrogen and phosphorus compounds, transforming them into less harmful substances. This occurs in the aeration basin.
  • Sludge Treatment involves pH balancing and dewatering the biosolids generated during wastewater treatment. These biosolids undergo further treatment to ensure their safety for specific disposal or repurposing. Once sludge has been properly treated, it can be sent to a landfill or used as an agricultural or landscaping fertilizer. Sludge treatment occurs during the solids handling step of the wastewater treatment process, after the previous steps have successfully separated it from wastewater.

The wastewater treatment process used by WWTPs depends on the requirements of each municipality and state, but the steps detailed below are an example of the conventional process used by many systems:

  1. Bar or Fine Screens: The first line of defense, bar or fine screens, removes large solids from sewage influent. These screens block unwanted waste from entering the system and prevent damage to downstream process equipment, such as pumps and clarifiers.
  2. Grit Removal: The screened wastewater then passes through the grit removal process, separating sediment and grit from the influent. This process protects downstream equipment and ensures a higher-quality influent for subsequent treatment steps.
  3. Primary Clarifier: Biological treatment's goal is to remove organics from wastewater, and primary clarifiers are where the initial sedimentation process takes place. By releasing wastewater from the clarifier's center along with a coagulant, organic matter falls to the clarifier’s floor, being collected by a skimmer or vacuum. This sludge is then conveyed to the solids handling portion of the process.
  4. Aeration Basins: Aeration basins leverage bacteria cultures and chemistry with aeration and anaerobic conditions to consume ammonia, nitrogen, and phosphorus. The bacteria cultures hasten the nitrification of ammonia and ultimately convert it into nitrogen gas, releasing it into the atmosphere.
  5. Secondary Clarifiers: Similar to the primary clarifiers, the secondary clarifiers remove the aeration basin’s remaining organics. Clear water proceeds to either tertiary treatment or disinfection while the sludge is sent to solids handling.
  6. Solids Handling: Once collected from the primary and secondary clarifiers, pumps convey sludge to the solids handling portion of the plant. The sludge is dewatered for cost-effective removal or treated for land application.
  7. Disinfection: Disinfection ensures wastewater effluent doesn't contain critical quantities of environmentally harmful bacteria. It's typically achieved with gas or liquid chlorination or Ultraviolet (UV) lights, effectively eliminating E. coli and other coliform bacteria.
  8. Monitoring and Testing: WWTPs diligently monitor wastewater quality throughout the treatment process. Test results of effluent samples, either done on-site or at professional laboratories, are reported to state and federal agencies to ensure compliance.
  9. Effluent Discharge: After undergoing treatment and disinfection, the wastewater effluent is discharged into local water bodies. These surface and groundwater bodies often serve as water sources for downstream water treatment plants.

PFAS Wastewater Treatment

The above wastewater treatment process has helped U.S. systems preserve water quality for decades, successfully removing many contaminants of concern. Unfortunately, conventional WWTP treatment methods are ineffective for PFAS removal. PFAS removal from wastewater requires separate steps to be performed in addition to the usual treatment process.

The specific methods used to remove PFAS vary depending on the waste stream. The table below lists the methods currently found to be most effective for each type of waste.

Wastewater Treatment Options Table

While effective, the above PFAS treatment methods all require extensive time, planning, and funding to implement. Municipalities with PFAS wastewater concerns will need to allocate significant resources to determine the appropriate treatment technologies to utilize, design and build new facilities, and continue monitoring and operating the new systems into the future. In fact, a new report published by the Minnesota Pollution Control Agency (MPCA) found that the technologies and expenses of removing PFAS from certain wastewater streams in Minnesota alone would cost between $14 and $28 billion over 20 years.

The potential cost of PFAS wastewater treatment will be challenging for many municipalities. Fortunately, utilities can explore cost recovery strategies to seek to make polluters, not ratepayers, cover the cost of PFAS cleanup.

Take Action to Mitigate Costs

If current trends continue, your municipality may soon be required to reduce the concentrations of PFAS contaminants in wastewater effluent and biosolids to maintain compliance with state and federal standards. By taking a proactive approach to your PFAS management strategy, you can be better prepared for potential upcoming regulations while also providing transparency and building trust with the public.

Based on current estimates, the costs of implementing PFAS wastewater treatment systems could be exorbitant. Since wastewater systems are the recipients of PFAS contamination, not producers or users, they should not have to bear the burden of cleanup costs. By seeking advice from a law firm with experience in water contamination litigation early in the process, you may be able to seek treatment cost recovery and protect the rights of your municipality.  

If you suspect that effluent or biosolids from your wastewater system may contain PFAS, you may want to seek help from a legal professional with experience in water contamination litigation to explore whether you may be able to seek to hold PFAS manufacturers accountable for the costs of wastewater treatment. SL Environmental Law Group focuses exclusively on contamination cases and works on a contingency fee, meaning that your utility only incurs legal expenses if a favorable outcome is achieved. Schedule a free consultation with SL Environmental Law Group to learn more about the available strategies to address contamination concerns.