Ian Mannix
Editor-in-Chief, Cosmos
Toxic metal contamination caused by the lead smelter at Port Pirie in South Australia’s mid north might be reduced with a new metals recovery method to be tested in the region.
The University of South Australia and InnovEco Australia are working on a project to recover copper, lead and zinc from tailing dams and clays using significantly less water and achieving much higher metal recovery rates than traditional methods.
The technology known as Resin in the Moist Mix (RIMM) can recover 90% of copper tailings compared to 75% with the traditional heap leach technologies.
The researchers say RIMM technology could potentially recover up to 3200t of lead and 4500t of zinc in river and creek sediments around the town.
The technique will also be used to rehabilitate the environment by removing other toxic compounds, including arsenic and cadmium from contaminated sites.
Port Pirie is a town of about 14,000 people. It is a regional service centre, but the biggest employer is the Nyrstar, the smelter’s owner, which describes the plant as one of the world’s largest multi-metal smelters, producing lead, silver and by-products such as sulphuric acid.
Zinc, lead and cadmium levels in the 15 kilometres surrounding Port Pirie are significantly higher than guidelines issued by the National Environment Protection Council, posing risks to human, animal and marine health, and degrading the local environment.
Lead smelter alongside cuttlefish playground
The South Australian Environmental Protection Agency says the Port Pirie River, river mouth and First Creek are at the centre of the metal contamination, with high surface sediment concentrations of lead, zinc, copper, cadmium and arsenic.
This pollution has entered the environment through emissions from smokestacks, dust blown from the site, the spillage of concentrates during the loading of ships, and effluent discharged to the Pirie River and First Creek.
This metal contamination decreases species diversity, resulting in biomass decline.
Surveys over the years have shown that many organisms in the gulf store elevated quantities of heavy metals, particularly lead, zinc and cadmium in their tissues. Concentrations of some metals in razorfish collected near Port Pirie were found to be above food standards. As a result, the collection of marine benthic molluscs has been prohibited.
The SA Department of Health Port Pirie Lead Implementation Program aims to help reduce the amount of lead that children and pregnant women are absorbing.
Recent reports show poor results in attempts to reduce lead contamination.
The National Health and Medical Research Council recommends that investigating and reducing sources of lead exposure if any person is found to have a blood lead level greater than 5 micrograms per decilitre (μg/dL), particularly if the person is a child or they are pregnant.
The program reports an improvement in the percentage of children with blood-lead levels above 5μg/dL.
However, there has been a deterioration in results across other age groups compared to 2022, including an increase in the number of children with blood lead levels equal to or above 20 μg/dL, placing them at the highest risk of health effects.
Associate Professor Larissa Statsenko from the University of SA who is developing the RIMM process, says the higher level of recovery will not only clean up the environment, helping it on the path to recovery, but also unearth millions of dollars’ worth of valuable metals in the process.
“Compared to existing rehabilitation technologies, the RIMM process is highly efficient, recovering almost all metals in a single step, while consuming less water and reagents, with a low environmental footprint,” says Statsenko.
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