The bacteria can break down and remove sodium oxalate, an organic impurity produced during the refining of low-grade bauxite into alumina.
The work is being presented for the first time in public through Fresh Science, a national competition for early-career scientists. Microbiologist Naomi McSweeney made the discovery in a project between Alcoa of Australia, CSIRO and the University of Western Australia.
At a typical refinery, sodium oxalate forms by the tonne during the production of alumina. It can affect the colour and the quality of the final product.
“Oxalate can be removed by combustion, but this process releases excess carbon dioxide”, Naomi said. The impurity may also be stored but this represents a major cost to refineries so treatment is a preferred option.
Alcoa of Australia has installed a large-scale bioreactor which has the capability to remove about 40t/day of sodium oxalate prod-uced at its Kwinana refinery in Western Australia.
The bacterial process breaks down the sodium oxalate and produces less CO2 while avoiding the need to store the impurity.
The scientists found a pote-ntially new genus of Proteobacteria and a new species of the known genus Halomonas which are able to use the carbon in the oxalate to grow.
To enhance the efficiency of the bio-removal process, the researchers are now determining the best conditions for growing these bacteria. Alcoa is seeking to apply the process to other refineries around the world.