PFAS Removal from Wastewater: Traditional vs Modern Treatment Methods

In the ongoing quest to combat water contamination, water and wastewater utilities face an evolving battlefield marked by pervasive pollutants like per- and poly-fluoroalkyl substances (PFAS). As federal and state environmental regulatory bodies tighten their grip on these modern chemicals to mitigate their impact on public health, the limitations of conventional wastewater treatment technologies become apparent. The 20th century's wastewater treatment processes, sufficient for the pollutants they target, fall short against a new generation of contaminants like PFAS. Proactively addressing modern water and wastewater pollution with more advanced technologies can help community leaders protect their water sources and be prepared for upcoming regulations.

In this article, we’ll illuminate the differences between conventional and advanced treatment technologies and their abilities to remove PFAS from water to serve as a guide for the type of technologies wastewater treatment plants may need in the 21^st century.

Traditional Methods for Wastewater Treatment

Traditional treatment techniques have managed wastewater pollution in cities across the world for over a century. They’ve proven effective at removing organic matter, bacteria, and other household contaminants from sewage to maintain the health of water bodies that provide communities with drinking water and recreation. However, these established methods show significant treatment deficiencies when confronted with PFAS. Sometimes referred to as “forever chemicals,” PFAS resist degradation and pass through the physical, chemical, and biological treatment processes that were designed for more organic pollutants. These treatment stages, effective at purifying sewage, fall short against PFAS' chemical resilience, failing to adequately destroy or remove these substances from wastewater.

Sedimentation and Filtration:

Physical treatments like sedimentation and filtration separate solids from wastewater. They act as filters that facilitate the efficacy of downstream treatment stages to ultimately comply with Clean Water Act standards. While physical treatment removes organic solids and nutrients, PFAS move onto subsequent treatment stages unabated due to their solubility in water, bypassing most physical barriers found at wastewater treatment plants. PFAS can be removed from wastewater via biosolids or filtered out by activated carbon and certain membrane filters common in water treatment. However, these processes do not destroy PFAS, leaving open the possibility for them to wind up elsewhere in the system.

Coagulation and Flocculation:

Chemistry plays an essential role in wastewater treatment. Chemical treatment processes like coagulation and flocculation facilitate physical and biological treatment methods, bringing certainty to a sensitive system. Coagulant is added to wastewater to bind naturally repelling organic materials to one another and stirred by “mixers” to form what are called “floc.” These heavier, agglomerated particles weigh themselves down to precipitate in the sedimentation stage.

Coagulation and flocculation are proven methods in treating typical sewage. However, the unique properties of the many PFAS chemicals make them immune to the binding properties of coagulants and polymers. Unaffected by the chemical treatment process, many PFAS remain dissolved in wastewater, though organic solids often harbor PFAS and are found in the biosolids handling stage of wastewater treatment.

Biological Treatment:

Wastewater treatment relies on thriving bacteria cultures fostered by aeration basins that mimic and accelerate the naturally occurring nitrogen cycle. These bacteria are fostered by aerobic and anaerobic zones that transform toxic substances like ammonia into nitrogen gas, which off-gasses into the atmosphere. While this process is routinely effective at removing ammonia, nitrogen compounds, and phosphorus from wastewater, it does not biodegrade PFAS compounds. PFAS’ robustness means they can pass through the biological treatment phase untouched as other pollutants diminish.

These traditional treatment methods, while effective against their original target contaminants, now obligate wastewater plants to shift towards more innovative technologies in order to meet the modern challenges posed by PFAS contamination and other contaminants of emerging concern. The adoption of modern treatment solutions may be unavoidable for these facilities to comply with regulations, protect public health, and stop the pollution cycle.

Modern Methods for PFAS Removal

In response to the treatment barriers posed by PFAS and other contaminants, the wastewater sector is increasingly turning towards solutions that complement and enhance traditional treatment methods. These modern approaches address the limitations of conventional techniques, promising effective PFAS removal from wastewater.

Membrane Bioreactors (MBRs)

Initially incorporated within the aeration basin to replace bulky clarifiers at space-deficient treatment plants, MBRs are a membrane filtration technology that effectively separate organic materials and PFAS from wastewater. MBRs provide a high level of wastewater purification without the footprint of a secondary clarifier. The membranes used in these systems feature micro-lesions that are so small that bacteria, viruses, and even PFAS cannot physically pass through them. This method enhances treatment performance and consistently ensures the physical separation of PFAS from wastewater. While MBRs deliver PFAS-free effluent that meets upcoming regulations, they do not destroy PFAS, leaving them and other contaminants to absorb into biosolids.

Granular Activated Carbon (GAC) Adsorption

Activated carbon reacts with almost everything. Its ability to absorb dissolved contaminants in water has made it a standout treatment for a wide array of pollutants, including PFAS. Commonly used in water treatment plants, wastewater plants wanting to remove PFAS from their effluent can employ these same carbon filter beds to facilitate a chemical reaction between activated carbon and the pollutants within wastewater. GAC effectively removes long-chain PFAS, is easy to procure, and relatively cost-effective. However, GAC systems often require the most space compared to other PFAS treatments, struggle to remove short-chain PFAS, and require longer retention times than ion exchange resins.

Further innovations, such as combining GAC with proprietary media like Fluoro-sorb™, show promise in enhancing PFAS removal rates, removing of a broader span of PFAS chemicals, as well as the lifespan of GAC media.

Advanced Oxidation Processes (AOPs)

AOPs are a cutting-edge approach against PFAS and other hard-to-treat chemicals, combining hydrogen peroxide with ozone or UV light to generate potent hydroxyl radicals. Hydroxyl radicals react with and break down PFAS molecules, rendering them into less harmful contaminants. This process dismantles the structural integrity that makes PFAS so challenging to treat and creates a pathway to significantly mitigate their environmental impact. AOPs offer a chance for treatment plants to destroy PFAS on site in addition to complying with environmental regulations. However, the consumption of hydrogen peroxide and ozone generation can be costly. Its practicality is case-by-case.

These modern treatment methods underscore a pivotal shift towards more effective strategies in combating PFAS contamination. However, they come with a financial burden not all communities are ready to take on.

Cost Effectiveness and Treatment Efficiency

Navigating the financial complexities of modernizing wastewater treatment facilities to address contamination requires innovative thinking and strategic planning. The shift towards advanced treatment methods, while necessary for environmental and public health, presents a significant financial undertaking for wastewater utilities nationwide. It’s critical to consult a professional engineer to analyze your contamination situation and determine the best method for your system. This involves a thorough analysis of treatment options, potential for scalability, and the long-term applicability of equipment investments in the face of increasingly stringent regulations.

A proactive approach coupled with an understanding of available cost recovery mechanisms can mitigate the financial burden. By exploring grants, state funding, and legal avenues for cost recovery, wastewater utilities can position themselves to effectively respond to the PFAS challenge without compromising their financial stability.

For communities that want to take on a proactive approach to removing PFAS from their wastewater, SL environmental law group offers a Cost Recovery Guide for Wastewater Utilities. If your community is interested in exploring how litigation against the manufacturers responsible for the PFAS contamination can fund the next generation of wastewater treatment equipment at your facility, contact us today for a free consultation.