Current PFAS Groundwater Treatment Technologies in Use

A lot has been happening over the past one to two years in the area of PFAS treatment technologies for groundwater and other media (e.g., soil, sediments); from lab-scale research and development, field-scale testing by the US Department of Defense (DOD) to actual implementation of technologies to treat drinking water at source by water purveyors.

Although it is not possible to describe in detail all the cutting edge and innovative technology development in this area, here is a brief summary of the commonly used PFAS treatment technologies in use with pros and cons. For additional details, questions, or for assistance with the design of a pilot or a full-scale PFAS treatment system, please reach out to me at [email protected].

The currently available and commercially viable technologies for treatment of PFAS in groundwater can be grouped under the following key categories:

• Sorption technologies (granular activated carbon or GAC and ion-exchange resins)
• Separation technologies (membrane filtration such as reverse osmosis and nano-filtration)
• Concentration technologies (foam fractionation and dissolved air floatation)
• Emerging destruction technologies (Electrochemical oxidation, Thermal treatment, UV light with photocatalysts, and Ultrasonic treatment)

Granular Activated Carbon (GAC) is widely used for PFAS removal due to its high porosity and large surface area:

• Effectiveness: Can be 100% effective for a period, depending on various factors
• Best for: Longer-chain PFAS like PFOA and PFOS
• Limitations: Less effective for shorter-chain PFAS like PFBS and PFBA

Anion Exchange Resins (AER) are highly effective for removing negatively charged PFAS contaminants:

• Effectiveness: High capacity for many PFAS
• Advantage: Single-use mode followed by incineration eliminates regeneration needs

Consideration: Typically more expensive than GAC

High-pressure membrane systems, such as nanofiltration and reverse osmosis, are effective in PFAS removal

• Nanofiltration: Uses membranes with ~1 nm pore size
• Reverse Osmosis: Pushes water through semipermeable membranes under high pressure
• Advantage: Can be used concurrently with other processes
• These systems are highly effective, typically removing more than 90% of a wide range of PFAS, including shorter-chain compounds.?However, they produce a concentrated waste stream (about 20% of the feed water) that requires further management.

Reverse osmosis (RO) and nanofiltration (NF) membrane systems are both highly effective for PFAS removal, but RO generally demonstrates superior performance:

RO membranes:

• Typically achieve removal rates well above 90% for a wide range of PFAS
• Can effectively remove both short-chain and long-chain PFAS compounds
• Some studies report PFAS rejection rates of 98-99%.

NF membranes:

• Also show promising results, with removal efficiencies often above 90%
• Performance can vary depending on the specific membrane and PFAS compounds
• Some NF membranes (e.g., NF90) have demonstrated >98% removal efficiency for 32 different PFAS species

Foam Fractionation and Dissolved Air Flotation

These liquid-solid separation technologies concentrate PFAS for easier removal. Both technologies exploit the surface-active nature of PFAS, but foam fractionation appears to be more specifically tailored for PFAS removal in various aqueous matrices.

Foam Fractionation

• Highly effective at removing long-chain PFAS compounds
• Low operational costs and energy requirements
• Generates a low volume of concentrated PFAS waste, reducing disposal challenges
• Works well with co-contaminants present in complex matrices like landfill leachate
• Scalable and adaptable to various industrial and municipal settings

• Less effective for short-chain PFAS removal
• May require chemical addition for low PFAS concentrations
• Requires a large footprint for equipment
• Effectiveness can vary depending on water quality and PFAS chain lengths

Dissolved Air Flotation

• Effective for removing suspended solids and some dissolved contaminants
• Can handle high flow rates
• Low energy consumption compared to some other treatment methods

• May be less effective for PFAS removal compared to foam fractionation
• Typically requires chemical additives to enhance performance
• Can produce a larger volume of sludge requiring disposal

The bottom line: Due to the various types of PFAS that will likely exist in a contaminated groundwater or leachate waste stream, a combination of technologies is typically needed. The best way to move forward is to conduct a pilot-scale study before committing significant capital expenditure to the project. Longer term operation and maintenance considerations can also play a role in the choice of technology(ies) selection including energy consumption.

December 1, 2024

Hari Gupta, PE

Principal Engineer - Coriolis Environmental Services

Former Cal EPA/Department of Toxic Substances Control - Senior Hazardous Substance Engineer