Fire-fighting foams have contaminated soils at fire-training and commercial sites across Australia and worldwide. Many foams contain per- and poly-fluoroalkyl substances (PFAS) chemicals, which can enter ecosystems and move through food chains, accumulating in animal and human bodies. There are thousands of PFAS-contaminated sites in Australia, many of which have growing stockpiles of polluted soil and a lack of cost-effective methods to remediate them.
‘We have developed a modified natural clay, called matCARE™, which attaches itself to toxic substances and binds them irreversibly,’ says Professor Ravi Naidu, Managing Director of the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE).
Prof. Naidu presented his findings this morning in Adelaide at CleanUp 2019 – the 8th International Contaminated Site Remediation Conference incorporating the 2nd International PFAS Conference, organised by CRC CARE and the University of Newcastle.
‘Our clay product is very effective at trapping PFAS in not only water, but also soil, which presents a more complex clean-up challenge. Once contaminated soil is treated, most of the PFAS is irreversibly locked up, preventing it from leaching into the environment. The technique is effective, sustainable and inexpensive,’ says Professor Naidu.
CRC CARE has successfully tested the soil remediation method in the field and in their laboratories. The field tests were done at a site used for fire training and emergency response for over 40 years. The researchers used a concrete mixer to treat the contaminated soil with a powdered form of matCARE.
‘Our measurements show significant reductions in the bioavailability of PFAS following treatment,’ said Professor Naidu, referring to the proportion of a substance that enters the circulation when introduced into the body – an indicator of human health risk. ‘The contaminant was locked up almost immediately. PFAS concentrations in water leaching from the treated soil are generally below detection levels.’
‘The alternatives to this stabilisation approach are expensive. Thermal treatment requires transport and energy intensive high temperatures. Soil washing with solvents can negatively affect soil structure.’
CRC CARE’s modified natural clay approach is consistent with the National Environmental Protection (Assessment of Site Contamination) Measure, federal legislation that promotes a risk-based approach to managing site contamination to ensure that remediation is both effective and economically viable. The protection measure sets out a preferred hierarchy of options for site clean-up and/or management and lists ‘on-site treatment of the contamination so that it is destroyed, or the associated risk is reduced to an acceptable level’ as the highest preference.
CRC CARE does research, develops technologies, and provides policy guidance for assessing, cleaning up and preventing contamination of soil, water and air. CRC CARE is hosting CleanUp 2019 in Adelaide from 8 to 11 September. Conference program at adelaide2019.cleanupconference.com/program.