Australian scientists are leading the way when it comes to cleaning contaminated water, with two new discoveries that could change how PFAS pollution and industrial wastewater are treated.
Concern about PFAS (per- and poly-fluoroalkyl substances) contamination has grown in Australia in the past few years, most notably around their use in legacy firefighting foams.
The chemicals, which don’t breakdown naturally and can travel long distances in the environment, have been found in groundwater and surface water sources across the country.
Powdered activated carbon (PAC) is one treatment method currently used to remove the pollutants from water; however, PAC has a tendency to cake and block filters and membranes, making the process expensive and complicated.
To help address this, researchers from the University of South Australia (UniSA) and Flinders University’s Institute for NanoScale Science and Technology created a new type of absorbent polymer made from waste cooking oil, which they added to the PAC process.
The new polymer adheres to carbon in a way that prevents caking, improving filtration speed and efficiency. It also lowers the amount of dust generated, which reduces the respiratory risks for those handling the material.
This new technique was tested on surface water near an RAAF base that had been contaminated with firefighting foam. The results, which were published in ACS Sustainable Chemistry and Engineering, showed the new filter material reduced the PFAS content of the water by 85%, from 150 parts per trillion (ppt) to less than 23 ppt.
The drinking water limit issued by the Australian Department of Health is 70 ppt.
Flinders University’s Dr Justin Chalker, who co-directed the study, said the polymer-carbon blend is a step in the right direction towards “safe, low-cost and versatile methods for removing PFAS from water”.
The next step is to test the technique on a commercial scale, said UniSA’s Dr Martin Sweetman.
“The activated carbon and polymer in this sorbent blend can, in principle, be made entirely from industrial waste and repurposed biomass, so it is very scalable and sustainable,” Sweetman said.
“Now we need to test it in purifying thousands of litres of water, but we are optimistic about the likely outcomes of such large-scale use.”
Australian researchers have also been instrumental in establishing a new method to filter contaminants from groundwater and industrial wastewater.
A team of scientists led by Professor Huanting Wang and Dr Huacheng Zhang from the Department of Chemical Engineering at Monash University has found a new way to separate certain negatively-charged ions, termed anions, from water using metal-organic frameworks (MOFs).
MOFs are made up of porous crystals with metal ions joined together by organic linkers. They contain molecular-sized pores that can store, separate, release or protect many substances, and can be scaled up to suit a variety of industrial purposes.
The team developed a MOF that is designed to be compatible with a specific anion. When it passes over the filter material, the selected anion is attracted to and easily passes through the pores, while other anions are largely unable to get through.
This is different to other water filtration techniques, where all forms of anions need to be removed and filtered to extract the unwanted substance. This is a costly and energy-intensive process that can mean some of the filtered ions must be added back into the water.
Wang said the method could produce simple and affordable water filters that can be used safely and effectively anywhere in the world.
“This is a significant outcome for people in developing countries who lack access to safe, clean drinking water, and for industries that are increasingly seeking ways to reduce the cost of their environmental impact,” he said.
“Our findings also prove we have the capability to determine the most effective filtering material and method to suit a specific material, or a particular industry need.”
The Monash team worked with researchers from the CSIRO, the University of Melbourne and the University of Texas at Austin.