TURNING MINE WASTEWATER INTO RAINWATER


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

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 commercial mine. The Virtual Curtain technology 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 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 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," says CSIRO scientist Dr Grant Douglas. "Reducing the amount 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 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 says.
Virtual Curtain utilizes 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 hydrotalcites could be formed by adjusting the concentrations of common wastewater contaminants, aluminium and magnesium, to an ideal ratio and then increasing the pH.

"By using contaminants already present in wastewater we have avoided the need for expensive infrastructure and complicated chemistry to treat it," he says. "If required, the treated water can be purified more efficiently via reverse osmosis and released to the environment or recycled back into the plant. It has huge benefits for mining operators in arid regions such as Australia and Chile.

"It is a more efficient and economical way to treat wastewater and is enabling the mining industry to reduce its environmental footprint and extract wealth from waste."

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