From soiled to soils: mining remediation a flushing success

16 Apr 2018
BR before and after.tif: comparison photos of bauxite residue before and after remediation

Sewage sludge is proving to be an unlikely ingredient in converting bauxite residue (a by-product of aluminium ore) into healthy soils capable of supporting plants.

A University of Queensland-led study has reported long-term mining industry success in transforming bauxite residue into soil using sewage sludge, green waste and other by-products.

Remediated bauxite residue supporting grass and tree vegetation cover

Senior Lecturer in Environmental Management in UQ’s School of Earth and Environmental Sciences Dr Talitha Santini led the research as part of a global study, investigating various bauxite residue remediation strategies over 10 to 40 years.

“The study, which aimed to identify the most successful approaches under different climates and for different residue types, involved eight alumina refinery sites across seven countries,” Dr Santini said.

“Around seven billion tonnes of tailings and processing residues are produced globally each year, with this figure likely to increase in future as ore grades decline and as demand for mineral and energy resources increases.

“Tailings and residues are the leftover portions of rock that has been mined and processed to extract mineral and energy resources.

“Australia is the world’s largest producer of bauxite (aluminium ore) and the second largest producer of alumina (which generates bauxite residue, an alkaline, saline tailings material, as a by-product), and has been leading the world in the development of remediation strategies for bauxite residue.”

Dr Santini said bauxite residue was transformed from an industrial by-product into healthy soil by making the soil pH more neutral, decreasing salinity, creating stable soil structure, and increasing plant nutrient concentrations.

“At a site in Texas, USA, over a 20 year period, sewage sludge, green waste, and other amendments were used to accelerate the transformation from residue into soil supporting a diversity of plants and which behaved like a naturally developed soil,” she said.

 “A number of other sites are now using or considering sewage sludge applications to accelerate remediation,” she said.

The project used the Australian Synchrotron in Melbourne to confirm the effectiveness of the amendments in permanently decreasing soil pH.

“My research group is continuing to build on this work as part of an ARC Linkage project supported by the International Aluminium Institute and Alcoa of Australia Limited,” she said.

The study, also co-authored by Professor Martin Fey of the University of Pretoria in South Africa, is published in the Journal of Soils and Sediments (doi: 10.1007/s11368-017-1867-1).

Media: Dr Talitha Santini, t.santini@uq.edu.au, +61 7 3365 6082, @talitha_santini

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