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Australia’s CSIRO investigating bioremediation of mine wastewater

1st February 2019

By: Nadine James

Features Deputy Editor

     

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Scientists from Australian research organisation the Commonwealth Scientific and Industrial Research Organisation (CSIRO) are using microbes and other methods to remove valuable metals and contaminants from mine wastewater, the organisation announced last week.

The technologies can process the water so that it is pure enough to be safely returned to the environment. The water can also be recycled and reused in mine production.

CSIRO environmental scientist Anna Kaksonen leads the research group. In the release, she noted that “certain microbes can help to either oxidise or reduce metals or other compounds, like sulphate, nitrate or selenate, so we can remove them from water”.

Further, microbes can also be used to clean up organic impurities and reduce acidity or alkalinity. “For example, wastewater from the alumina industry has a lot of organic impurities that can accumulate in the water used in ore processing.”

She explained that biological treatment could be combined with other processes like hydrotalcite precipitation to deliver a more effective clean-up than either process can do alone.

The hydrotalcite – anionic clay – precipitation process, invented by the CSIRO’s Grant Douglas and licensed to Virtual Curtain, involves adding a patented mixture into the wastewater, which then binds to metals and other contaminants as it forms hydrotalcite.

Contaminants are easily removed from the wastewater as a well-settling sludge containing valuable metals in highly concentrated compounds, the release states.

Introducing biological processes after the hydrotalcite precipitation could facilitate the removal of other contaminants remaining in the water, such as sulphate and nitrate, commented Kaksonen, adding that the same treatment processes used plant materials or even wetland plants to provide a continuous carbon and energy source for the microbes.

“These biotechnologies mimic natural systems, but they are designed to provide optimum conditions to clean up wastewater.”

“Most of our work has two dimensions,” CSIRO senior research scientist Dr Ka Yu Cheng, added. “First, we aim to understand how the biology works in the environment now, [and then] we try to engineer the process so that microbes can work better to achieve what we want them to do – such as finding the right mix of plants, the right temperature or the right pH to increase the activity of the microbial community.”

The CSIRO team uses DNA analysis to identify the type of microbes that exist in mine water. Then they search through large databases to collate more information on these microbes.

Sometimes the team conducts research using microorganisms from commercial culture collections, which include micro-organisms gathered by scientists globally.

The team also do their own “bioprospecting” – exploring various places both natural environments and contaminated sites to find microbes that thrive in harsh environments.

“We take samples from mine sites, existing wastewater treatment processes or sediments,” Kaksonen noted, adding that “there could be some synergies for using waste from one industrial sector as a feed stock for another sector”.

She pointed to industrial symbiosis occurring between biodiesel and mining industries, “moving both industries toward a more circular economy”.

The CSIRO team recently tested their biotechnology processes in the laboratory. They are now working with Evolution Mining to develop better treatment solutions for the wastewater at the company’s Mt Rawdon gold mining operation, in Queensland.

“The company is planning to use a wetland system to treat mine wastewater. The CSIRO’s team will compare the effectiveness of sawdust, plant material, ethanol and lactate to find the best material that can support the microbial treatment in a wetlandlike system,” Cheng said.

“The mine wastewater from Evolution’s mine will contain sulphate and metals, so we are working with the company to combine hydrotalcite precipitation and biological sulphate reduction,” Kaksonen added.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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