Texas A&M study highlights hidden PFAS risks in wastewater filters

Researchers at Texas A&M University have identified an overlooked challenge associated with wastewater filters used in advanced water recycling systems.

Their study found that per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals”, accumulate in significant quantities on reverse osmosis filtration membranes during years of operation.

The research examined a full-scale potable water reuse facility where treated municipal wastewater is purified to drinking water standards.

While the treatment technology successfully removes PFAS from the water itself, the study shows that the contaminants become concentrated on the filtration membranes throughout their service life.

The findings raise important questions about how ageing wastewater filters should be handled, cleaned and disposed of.

Without appropriate end-of-life management, accumulated PFAS could expose workers during maintenance or potentially enter the environment if discarded improperly, providing new evidence to inform future regulations and disposal practices.

Examining long-term PFAS accumulation

Published in the Journal of Membrane Science, the research was carried out by scientists from Texas A&M University’s Department of Civil and Environmental Engineering alongside an industry collaborator from Arcadis.

The team analysed commercial reverse osmosis membranes that had operated continuously for four years at a municipal potable reuse facility.

Reverse osmosis is widely used in advanced water treatment because it forces water through highly selective polymer membranes, effectively removing salts, minerals and chemical contaminants, including PFAS.

However, wastewater entering these facilities typically contains much higher PFAS concentrations than conventional freshwater sources, meaning the membranes are exposed to persistent chemical loading throughout their operational lifetime.

Rather than investigating contaminants remaining in treated water, the researchers focused on the filters themselves to understand how these chemicals behave after removal.

Organic fouling plays a key role

The study found that long-chain PFAS compounds accumulated primarily on organic and biological fouling layers that naturally develop on membrane surfaces during operation.

These biofilms, made up of proteins, sugars and microorganisms, appear to provide favourable conditions for trapping persistent contaminants.

Researchers found that long-chain PFAS represented around two-thirds of the total chemical mass captured during the early filtration stages.

PFAS precursor compounds, which can later transform into more stable PFAS chemicals, accounted for a further 14% of the accumulated material.

In contrast, the final stage of the treatment process showed very little PFAS retention. At this point, membrane surfaces were dominated by mineral scaling rather than organic fouling, suggesting that the type of deposits forming on the membranes has a major influence on contaminant accumulation.

Implications for wastewater filters and water utilities

The findings suggest that the environmental footprint of wastewater filters extends beyond their ability to purify water.

As potable reuse systems become more common in regions facing water shortages, utilities will increasingly need strategies for safely managing thousands of filtration membranes reaching the end of their operational lives.

The study provides engineers with valuable data that could support the development of improved membrane cleaning methods, safer disposal procedures and more comprehensive life cycle assessments for advanced water treatment technologies.

The researchers also note that extending membrane lifespan alone will not eliminate the challenge, as PFAS captured during years of operation must still be managed responsibly when filters are eventually replaced.

As investment in water recycling continues to grow worldwide, the research highlights the importance of considering the complete lifecycle of wastewater filters.

Understanding how PFAS accumulates on treatment membranes could help shape future engineering practices, environmental regulations and waste management policies while ensuring advanced water purification systems remain both effective and environmentally sustainable.