New technology to treat mining wastewater

CSIRO has developed cost-effective technology, called Virtual Curtain, which can treat mining wastewater and reduce sludge by up to 90%.

Dr Grant Douglas, a senior principal research scientist at CSIRO, said the technology has been used for the first time at a commercial mine, where it was used to remove metal contaminants from wastewater.

“The Virtual Curtain technology was used to treat over 50 ML, or in excess of 20 Olympic-sized swimming pools, of contaminated water,” Dr Douglas said. “After treatment, the majority of this water was then released safely to the environment.”

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

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, thus simplifying mine wastewater treatment.

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.”

The mine pit following the release of the treated water.

Virtual Curtain technology is a departure from the conventional lime-based treatment methods which have been used in the mining industry for many years, producing “only a fraction of the sludge” according to Dr Douglas.

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

Furthermore, he said, the technology can produce an ore-like material, “high in metal value, which can be reprocessed to increase a miner’s overall recovery rate and partially offset treatment costs”.

“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,” he said.

The licensed technology can be applied to a range of industrial applications and is available through Virtual Curtain Limited.

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