New PFAS treatment method features nanofiltration

Chris EdwardsDecember 12, 2022, 8:21 amAugust 15, 2023

Hydroflux, an Australian water treatment specialist for groundwater remediation, has developed a ZeroBrine membrane process utilising HyPURE NX nanofiltration systems to treat PFAS in groundwater.

Water treatment specialist Hydroflux has developed a new process to treat PFAS in groundwater. The process can be implemented on new and existing GAC, IX and SAFF systems to reduce operating costs for treating long and short-chain PFAS. The technique also provides environmental benefits through a reduction in energy use. It also avoids the use of pre-treatment chemicals required for traditional filtration processes.

What are PFAS Compounds?

PFAS is a group of synthetic chemicals known as per- and poly-fluoroalkyl substances. The hallmark of PFAS compounds is their series of carbon-fluorine bonds, which form part of the “backbone” of these chemicals. The backbone is typically combined with a carboxylic or sulfonic acid functional group. There are some notable exceptions to this, such as Gen X compounds. The high energy required to break the carbon-fluorine bonds within PFAS substances means they are virtually indestructible, making them ideal for various industrial uses. These products have been used in everything from firefighting foams and Teflon to grease-resistant coatings in carpets and chip packets.

The major challenge with these compounds is that they do not break down in the environment. It leads to bioaccumulation within animals and humans. PFAS molecules are also highly mobile due to their hydrophilic carboxylic acid and sulfonic acid functional groups, enabling them to travel thousands of kilometres in groundwater and surface water. The combination of their ability to bioaccumulate and mobility has led to a global phase-out of these products.

While PFAS compounds are not manufactured in Australia, they are still in use and are present in a range of imported consumer products. One of the primary sources of PFAS contamination is firefighting foams. The sale and use of PFAS firefighting foams are banned in South Australia, and New South Wales introduced a range of restrictions in March last year (2021).

Due to its mobility and persistence, PFAS contamination in the environment from firefighting foams, alongside other sources, are widespread across Australia. The current EPA national environmental management plant for PFAS recommends treating PFOS to 0.00023 µg/L (0.23 ng/L) and PFOA to 19 µg/L before environmental discharge.

Existing Treatment Methods

Currently, many treatment technologies are used to remove PFAS from the surface and groundwater. Many of these solutions are only functional on a small scale. Alternatively, these solutions treat highly concentrated waste due to the high energy requirements to operate at extreme temperatures or pH ranges to break down C-F bonds.

Several proven treatment methods exist, including activated carbon (GAC) and/or ion exchange (IX) adsorption and foam fractionation. These technologies have proven effective at PFAS removal when incoming concentrations are high. However, the level of reliability reduces at very low concentrations (1 – 5 ng/L) while operating costs increase. All technologies also struggle to remove short-chain compounds such as PFBS.

Reverse osmosis and nanofiltration membranes remove PFAS compounds, even at low incoming concentrations (1 – 5 ng/L). However, managing waste brine creates a serious and currently unresolved challenge.

HyPURE NX ZeroBrine nanofiltration process for PFAS removal

Hydroflux has developed a process that exploits the benefit of the physical barrier to PFAS compounds offered by nanofiltration membranes without the challenge of handling waste brine. The ZeroBrine process utilises the company’s HyPURE NX system fitted with NX Filtration direct hollow fibre nanofiltration membranes at its core.

The NX Filtration dNF40 and dNF80 membranes are effective at removing PFAS compounds. The pore sizes and unique nanocoating within the membrane are structured to retain PFAS and other organic pollutants while allowing dissolved inorganic salts to pass through.

The HyPURE NX ZeroBrine process can also be retrofitted to existing GAC, IX and foam fractionation systems. It can provide improved treatment performance, reliability and savings in operating costs. The membrane provides a barrier to remove a range of PFAS compounds.

Removal of Co-Contaminants

One of the benefits of the HyPURE NX system is that it removes a broad spectrum of other contaminants in a single process. That means other targeted treatment systems do not need to be provided. Some of the many compounds removed by the HyPURE NX system are: