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Accidental events in Hungary on Monday 4th of October
In the light of the accidental events in Hungary on Monday 4th of October involving a bauxite residue deposit, the European Aluminium Association is fully committed to assist in the assessment of the situation and the origins of this tragedy.
“Our thoughts go to the families of the victims in Hungary. The aluminium industry is keen to understand the exact causes of this accident so all security measures are in place to prevent these unprecedented circumstances ever happening again” said Patrick de Schrynmakers, EAA Secretary General.
The EAA has no additional information at this time as the Ajka Alumina Plant is not operated by one of its member companies. However, our Association, in line with its mission to foster the dissemination of best practices, is ready to provide its expertise as necessary.
The EAA stresses that an EU Best Available Techniques Reference Note on mining waste deposits already exists, with clear guidance on how bauxite residue deposits needs to be constructed and maintained. Deposits like this have been in operation for a long time without any incidents of this type to date.
Bauxite residue material is the by-product of the Bayer process, an industrial chemical process for refining aluminium containing ores (bauxites) into alumina (aluminium oxide) via digestion with sodium hydroxide (caustic soda). Alumina is the raw material for production of aluminium metal and has important uses in the ceramics and pharmaceutical industries.
Bauxite residue material is often described as red mud due to the colour of the original bauxite ore and the iron oxide it contains. The unexpected and sudden discharge of a large volume of this material would have the same disastrous impact as any mud slide or dam burst, subject to local geography. The residue normally has an elevated caustic content (i.e. a pH of between 10 and 12) although refineries try to recover as much caustic soda as possible and neutralise the residue during post-processing treatment to be able to reuse this valuable material in the alumina production process.
The normal practice for deposits is to have a bottom and side lining to prevent liquid from leaking into the ground and surrounding areas. The residue caustic soda and water is pumped back to the plant for reuse in the process. Surrounding the deposit are purpose-built retaining walls to keep the residue in place and prevent any leakage. The walls are regularly inspected and maintained.