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Australian Scientists Turn Mine Sludge Into Rainwater

The new treatment in progress to remove a range of metal contaminants. Image: CSIRO

A new cost-effective technology to treat mining wastewater and reduce sludge by up to 90% has been used for the first time at a copper mine in Queensland.

The Virtual Curtain technology removed metal contaminants from wastewater at the Baal Gammon mine and safely discharged the equivalent of 20 Olympic swimming pools of rainwater-quality water.

Sludge is a semi-solid by-product of wastewater treatment and reducing the amount produced has huge environmental and economic benefits.

“Our treatment produced only a fraction of the sludge that a conventional lime-based method would have and allowed the mine water to be treated in a more environmentally sound way,” CSIRO scientist Grant Douglas said.

The Australian mining industry generates hundreds of millions of tonnes of wastewater each year.

“The technology can produce a material high in metal value, which can be reprocessed to increase a miner’s overall recovery rate and partially offset treatment costs,” Dr Douglas said.

Virtual Curtain utilises hydrotalcites, which are minerals sometimes found in stomach antacids, to simultaneously trap contaminants including arsenic, cadmium and iron.

Dr Douglas and his team developed the technology after discovering that hydrotalcites could be formed by adjusting the concentrations of common wastewater contaminants, aluminium and magnesium, to an ideal ratio and then by increasing the pH.

“By using contaminants already present in the wastewater we have avoided the need for expensive infrastructure and complicated chemistry to treat the waste,” he said.

The licensed technology, which can be applied to a range of industrial applications, is available through Australian company Virtual Curtain Limited.

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