Companies like RemBind are focusing on the contaminants found in biosolids, including PFAS. Managing Director Richard Stewart provides an insight into RemBind’s solutions.
Many people will have heard of PFAS, officially known as per- and polyfluoroalkyl substances. Often dubbed the ‘forever chemicals’, these are a group of synthetic chemicals that accumulate in the environment, and there is some evidence to show that a subset of these compounds can cause toxicity to human health and the environment.
These chemicals have been used in firefighting foams, non-stick cookware, and waterproofing agents, among many other products.
What are biosolids?
Biosolids are nutrient-rich organic materials that result from treating raw sewage sludge during wastewater treatment processes. Biosolids can be beneficially reused on agricultural land, as they not only provide a valuable source of nutrients but can also help improve other soil properties.
However, wastewater treatment processes tend to also concentrate some environmental contaminants, such as heavy metals and PFAS. The detection of PFAS contaminants in biosolids has received significant media attention recently because biosolids have been applied to some land and pastures for decades, and the associated PFAS loads have been largely uncontrolled.
Stabilisation of PFAS in biosolids — A viable approach
Stabilisation (also called ‘immobilisation’) refers to adding inert minerals to biosolids to ‘lock up’ the PFAS contaminants to prevent them from leaching into groundwater, where they can cause harm to human health and the environment.
The immobilisation process is relatively cost-effective and practical, and the treated biosolids can still be used on agricultural land for beneficial reuse. The technology can also be applied in situ to reduce PFAS uptake into plants.
Since 2013, RemBind has used its sorbents to lock up PFAS in soils, including at US Air Force bases. Now, the same tech can be applied to biosolids to allow beneficial reuse in agriculture.
PFAS stabilisation in sewage sludge
Recent research has highlighted the urgent need to address the environmental challenges posed by PFAS. Novel strategies using sorbents have emerged as promising solutions to mitigate PFAS contamination in agricultural practices.
One 2023 study demonstrated the positive effects of sorbents in reducing PFAS leaching from sewage sludge. At addition rates of less than two per cent, RemBind 100X showed the best stabilisation performance. During the 115-day study, the leachable PFAS fluctuated in the leachate of sludge amended with RemBind 100X, implying a dynamic adsorption/desorption process.
In a second study, the researchers showed that the application of RemBind sorbents significantly reduced the uptake of PFAS into grass grown in biosolids-amended agricultural soil. This study helped validate the in situ application of sorbents to lower PFAS bioavailability in crops and decrease PFAS movement to vulnerable biota and water.
This independent data has given RemBind confidence that it can be used to stabilise PFAS in biosolids. It provides peace of mind to future generations that there exists a tech that can potentially help protect their food sources from PFAS.
Biosolids feature in the latest Australian PFAS guidelines
The latest version of the PFAS National Environmental Management Plan (NEMP) was publicly released in March 2025 and specifically mentions biosolids for the first time. The PFAS NEMP provides nationally agreed guidance on managing PFAS environmental contamination, including preventing its spread.
While the reuse criteria are based on total PFAS concentrations, reducing the leachable concentrations using stabilisation represents a viable risk-based approach for the beneficial management of biosolids.
It is crucial to continue exploring innovative strategies and technologies that ensure environmental safety and support the sustainable reuse of vital resources in agriculture.
For more information, visit rembind.com
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