Notable case, Ajka / Kolontár, Veszprém, Hungary

Ajka red mud spill (Kolontár and Devecser)

Ajkai vörösiszap-katasztrófa

On 4 October 2010 a red-mud reservoir at the Ajka alumina plant failed: about one million cubic metres of mud at pH 13 swept through Kolontár and Devecser, killing ten people.

Status: Remediated
Area: 4,000 ha on land¹
People affected: 416 (2010)²
Media: soil, surface water, sediment
Kind of site: smelter, accident, chemical works

Area. 40 km² affected according to Wikipedia; Hungarian literature gives about 800 ha of land flooded by the mud.
People affected. 10 dead and 406 injured.

Contaminants

Metals

Metalloids

Arsenic

Other inorganics

Red mud (alkaline)

Status

Remediated

The mud was removed from fields and villages; the review by Makó et al. (2025) judges the clean-up effective, with a small part of the area still at significant risk. The alumina plant was producing again by mid-October 2010.

Story

The Ajka plant, owned by MAL Magyar Alumínium, made alumina from bauxite by the Bayer process. The residue, red mud, is a strongly alkaline slurry of iron (40–45%) and aluminium oxides, with sodium and traces of chromium (660 mg/kg), arsenic (110 mg/kg) and mercury.

On 4 October 2010, at 12:25, the corner of a storage reservoir gave way. About one million cubic metres of mud poured into the Torna stream and over the villages of Kolontár and Devecser. Ten people died and 406 were injured, 120 seriously, mostly from chemical burns. The mud reached the Marcal and Rába rivers and, on 7 October, the Danube.

The state took control of the company on 13 October. The mud was scraped off the land; where the layer was thin, deep ploughing was used with soil improvers and bacterial fertiliser. In 2016 the director and 14 employees were acquitted; in 2019 a court convicted ten people for breaching safety rules.

Timeline

20104 October: the reservoir fails; 7 October: the mud reaches the Danube; 13 October: the company is put under state control.
2016The director and 14 employees are acquitted at first instance.
2019Ten managers and employees are convicted.

Health

Ten deaths and 406 injured, 120 of them seriously, mostly burns from contact with the alkaline mud (figure as reported by Wikipedia).

Remediation

2010excavationRemoval of the mud and vegetation from meadows and arable land.
2011deep ploughing and soil amendmentDeep ploughing where contamination was light, with soil improvers and bacterial fertiliser.

From the literature

Species that acted on one of this site's contaminants in at least one study. The list is automatic and takes no account of this site's soil, concentrations or climate.