What Are PFAS?
PFAS are man-made chemicals designed for durability. Their defining characteristics include:
- Water and oil repellence
- Heat resistance
- Chemical stability
These properties led to widespread use in:
- Firefighting foams (particularly at airports and defence sites)
- Non-stick cookware
- Stain-resistant fabrics and carpets
- Industrial processes
However, these same properties also mean PFAS do not easily break down in the environment, leading to long-term contamination risks.
PFAS in Australian Drinking Water
Unlike some contaminants, PFAS are not routinely monitored across all Australian water supplies. However, targeted studies provide insight into their occurrence:
- Around 50% of samples in a national study were below detection limits
- Detected concentrations included:
- PFOS: 0.66–16 ng/L
- PFHxS: <0.92–14 ng/L
- PFOA: <0.5–9.7 ng/L
While these levels are generally low, localised contamination (e.g., near firefighting training areas) can be significantly higher.
Australian Drinking Water Guidelines (ADWG)
Australia regulates PFAS in drinking water through health-based guideline values:
- PFOS + PFHxS (combined): < 70 ng/L
- PFOA: < 560 ng/L
These limits are designed to protect public health over a lifetime of exposure. Importantly, they are precautionary values, reflecting the uncertainty around long-term health impacts.
Why PFAS Are So Challenging
PFAS pose unique challenges compared to conventional contaminants:
- Persistence
They resist natural degradation in soil and water. - Mobility
PFAS can travel long distances in groundwater systems. - Treatment limitations
Many standard water treatment processes are ineffective.
Ineffective Treatment Methods
Conventional processes typically do not remove PFAS, including:
- Coagulation and sedimentation
- Sand filtration
- UV disinfection
- Chlorination
- Advanced oxidation processes
This makes PFAS fundamentally different from pathogens and many organic contaminants.
Effective PFAS Treatment Technologies
Despite these challenges, several treatment methods are proven to reduce PFAS concentrations:
1. Activated Carbon (PAC & GAC)
Activated carbon works through adsorption, trapping PFAS molecules on its surface.
- Powdered Activated Carbon (PAC):
- Effective for long-chain PFAS
- Requires higher doses and contact time
- Generates contaminated sludge
- Granular Activated Carbon (GAC):
- Widely used in water treatment plants
- Removal efficiency: 66%–100% depending on PFAS type
- Requires periodic replacement as media becomes exhausted
Key limitation: PFAS are removed from water but not destroyed—they remain in the carbon media.
2. Ion Exchange Resins
Ion exchange (IX) resins remove PFAS via electrostatic attraction.
- Particularly effective because PFAS molecules are negatively charged
- Smaller footprint than GAC systems
- High efficiency (up to ~95% removal depending on type)
Challenge: Resin regeneration produces waste streams that require careful disposal.
3. Membrane Filtration (NF & RO)
Nanofiltration (NF) and Reverse Osmosis (RO) are the most effective technologies:
- Remove both short- and long-chain PFAS
- Achieve removal rates of:
- NF: >95%
- RO: >99%
- Use size exclusion and electrostatic mechanisms
Trade-offs:
- High energy consumption
- Production of a concentrated waste stream (reject water)
A Critical Issue: PFAS Are Not Destroyed
A key takeaway for engineers and policymakers:
Most treatment technologies transfer PFAS from water to another medium—they do not eliminate it.
This creates secondary challenges:
- Disposal of contaminated carbon or resin
- Management of RO reject streams
- Long-term environmental liability
Emerging technologies aim to destroy PFAS molecules, but these are still under development.
The Australian Context: What Needs to Happen Next
Australia faces a balancing act between risk, cost, and practicality. Key priorities include:
1. Improved Monitoring
Routine PFAS testing across all water supplies would provide better risk visibility.
2. Site-Specific Risk Management
High-risk areas (e.g., near defence sites) require targeted interventions.
3. Technology Selection
Utilities must weigh:
- Removal effectiveness
- Cost
- Waste disposal requirements
4. Research and Innovation
Investment in technologies that destroy PFAS, rather than relocate them, is essential.
Final Thoughts
PFAS contamination represents a new generation of water challenges—complex, persistent, and costly to manage. While Australia’s drinking water remains generally safe, localized contamination and evolving health concerns require continued vigilance.
For engineers, PFAS is not just a treatment issue—it is a systems problem, involving monitoring, regulation, treatment design, and long-term waste management.