12 June 2014

Turning mining wastewater into rainwater

A new cost-effective technology to treat mining wastewater and reduce sludge by up to 90 per cent has been used for the first time at a commercial mine.

Turning wastewater into rainwater

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[Music plays and text appears: Turning wastewater into rainwater. A new, cost-effective treatment process for the mining industry]

[Image changes to show Dr Grant Douglas, Senior principal research scientist, CSIRO]

Dr Grant Douglas: The Virtual Curtain technology represents a new concept in the treatment of mining wastewaters. In a recent first commercial application at a mine site the Virtual Curtain technology was used to successfully treat over 50 mega litres or an excess of 20 Olympic size swimming pools contaminated water.

[Image changes to show a mine site and the water treatment plant and then moves back to Dr Douglas]

After treatment the majority of this water was then released safely to the environment.

[Image changes to show aerial shots of a mine site]

While lime has been around for many years and is used almost as a default in the mining industry, the Virtual Curtain technology often produces substantially less sludge than the lime, lime-based amendment and then with that there’s the opportunity to form and enriched, almost ore-like material which can be re-mined to offset costs.

[Image changes to show the lime-based sludge and then moves back to Dr Douglas]

The technology is based on the formation of a mineral known as a hydrotalcite.

[Image changes to show a computer generated graph of the hydrotalcite process]

The hydrotalcite is formed from elements already present in the wastewater itself. During its formation the hydrotalcite can simultaneously incorporate a wide range of contaminants, often in a single step, thus simplifying mine wastewater treatment.

[Image changes to show a mine site and a body of water]

In using the new technology an opportunity exists for mining companies to extract and adopt a wealth from waste philosophy, and in so doing also reduce their wastewater treatment costs and environmental footprint.

[Music plays and CSIRO logo appears with text: Big ideas start here www.csiro.au]

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The technology, called Virtual Curtain, was used to remove metal contaminants from wastewater at a Queensland mine and the equivalent of around 20 Olympic swimming pools of rainwater-quality water was safely discharged.

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 Dr Grant Douglas said.

“Reducing the amount of sludge is beneficial because the costly and timely steps involved to move and dispose it can be reduced.” 

Given the Australian mining industry is estimated to generate hundreds of millions of tonnes of wastewater each year, the technology opens a significant opportunity for companies to improve water management practices and be more sustainable.

“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 a variety of contaminants – including arsenic, cadmium, and iron – in one step.

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.

“If required, the treated water can be purified much more efficiently via reverse osmosis and either released to the environment or recycled back into the plant, so it has huge benefits for mining operators in arid regions such as Australia and Chile.

“It is a more efficient and economic way to treat wastewater and is enabling the global mining industry to reduce its environmental footprint and extract wealth from waste.”

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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