Ultromex will partner with French waste management company EJM Hydrovac on the project to excavate and process 65,000 tonnes of salt slag waste at the site.
An Ultromex plant will be during 2021 that will be capable of processing the waste at a rate of 18 t/hr.
"The signing of this major contract is the result of more than three years hard work by the Ultromex and EJM teams, including a pilot trial which validated and demonstrated to Rio Tinto the effectiveness of our Saltromex process for remediating slag," said Nigel Seddon, chief executive of Ultromex.
The company's Saltromex technology enables aluminium smelters to treat and recycle their own salt slag wastes, with aluminium and flux salts also recovered and only non-odourous, valuable aluminium oxide residues left.
Many aluminium smelting wastes are hazardous in nature and historically were routinely landfilled before the EU and other regions changed regulations to prohibit further landfill.