University of Newcastle researchers are using heat to remove PFAS and other contaminants from wastewater sludge so it can be safely used for agricultural purposes.
Almost 350,000 tonnes of dry biosolids, or treated sludge from wastewater, are generated annually in Australia.
While the material is a significant potential new nutrient source for the agriculture industry, heavy metals and emerging contaminants, particularly PFAS, are putting a considerable constraint on its use.
A team at the University of Newcastle, led by Distinguished Laureate Professor Ravi Naidu and Dr Yanju Liu, has been awarded $919,840 from the Cooperative Research Centre (CRC) for High Performance Soils.
The research will investigate if the thermal conversion of biosolids to biochar, the charcoal created when burning organic materials, creates a safe nutrient source for agricultural use.
While biosolids have been used as a rich source of nutrients for a some time, the recent discovery of the presence of PFAS in these materials has led to a ban on the use of biosolids in farming.
As a result, millions of tonnes of biosolids are being stockpiled in countries globally.
This project aims to determine if turning biosolids in biochar will remove organic emerging contaminants ensuring its safe use as a slow-release fertiliser. It will also look at the benefits of biochar to soil health and soil texture improvement.
This research will be critical for both the water and agriculture industries by providing strategies to use a current waste product as a viable and cost-effective fertiliser. It will be significant in assisting to minimise the biosolid stockpiles, leading to a reduction of billions of dollars in management costs.
A study found the presence of PFAS chemicals in 53 fruit and vegetable samples collected from a wholesale and retail market in Sydney and a supermarket in Newcastle.
The highest concentrations were found in garlic, parsley and dill.
PFAS were also found in broccoli, kidney beans, carrot, spinach, bitter gourd, cucumber, bok choy, pumpkin, okra, bean sprouts and lettuce.
Six PFAS chemicals were tested and results showed that the concentrations of these contaminants depended on the type of PFAS chemical and the type of vegetable.
Professor Naidu heads crcCARE [Cooperative Research Centre for Contamination Assessment and Remediation of the Environment].
It is also examining PFAS in soil and water and developing techniques to remove them, or at least make them safe.
The researchers examined how PFAS were getting into vegetables.
"We figured out that many of our vegetable farmers have been using alternate sources of nutrients such as biosolids, manure, composts and they are the source of PFAS."
