Evolution and CSIRO join forces
CSIRO scientists have teamed up with Evolution Mining to explore the use of microbes and other methods to remove valuable metals and contaminants from mine wastewater.
Microbes – which are essentially very small (microscopic) organisms such as bacteria – could help either oxidise or reduce metals or other compounds, like sulphate, nitrate or selenate, so they can be removed from water.
“CSIRO has been evaluating the efficiency of various organic substrates, such as plants saw dust, lactate and ethanol to promote biological sulfate reduction for removing sulfate from mine water,” CSIRO Biotechnology and Synthetic Biology group leader Anna Kaksonen said.
“We’ve also evaluated the treatment of the mine water with hydrotalcite precipitation treatment of Virtual Curtain, also developed by the CSIRO.”
Dr Kaksonen said at Evolution Mining’s Mt Rawdon mine in QLD, the team had been developing biological sulfate reduction based processes for mine water treatment.
“We were approached by Evolution Mining to trial Virtual Curtain hydrotalcite precipitation, which opened an opportunity to explore bioremediation as a compatible treatment that could potentially lead to better results,” she said.
“Additionally, in a strategic CSIRO project we have developed biotechnical processes for removing selenate, nitrate and sulfate from mine waters.”
Dr Kaksonen said CSIRO’s Virtual Curtain technology – which removed various metals from water and neutralised acidity – could be used as a pre-treatment to remove toxic contaminants before biotechnical treatment.
“In this study we have found that the combined use of the Virtual Curtain technology and biotechnical processes gives the best treatment outcome,” she said.
However, Dr Kaksonen said while some mining companies have trialled wetland systems and various biotechnical processes, most mine sites still used chemical treatments to clean up mine water.
She added a constructed wetland could potentially be a cost-effective process to treat water to a stage where it was safe to release back into the environment.
The idea would be to construct a wetland while the mine is operating, which would form part of the mine closure plan.
“Biotechnical processes have many advantages when compared to traditional chemical treatments,” Dr Kaksonen said.
“I think there is potential for using biotechnical system (such as wetlands or bioreactors) more broadly.
“The selection of the process would need to be done on a case-by-case basis depending on the water characteristics, climate and availability of suitable organic substrates to promote biological treatment.”