On October 4, 2010, approximately one million cubic meters of red mud was released from an alumina plant near Kolontár, in western Hungary. The ecological disaster occurred when the northwestern corner of the caustic waste dam at the Ajkai Timföldgyár alumina plant collapsed, releasing liquid waste from the red mud lakes. Red mud is a solid waste product of the Bayer process, which is the way industries refine bauxite to produce alumina. Alumina is then used in the production of aluminum metal. The toxic material presents one of the industry’s most challenging disposal problems. In most countries where red mud is produced, it is pumped into holding ponds, which need to be contained with large dams.
Due to the Bayer process, the red mud is highly basic with a pH ranging from 10 to 13. During the 2010 Ajka accident, the red mud was released as a 1–2 m (3–7 ft) wave, flooding several nearby localities, including the village of Kolontár and the town of Devecser. The high pH levels of the mud caused severe chemical burns to humans and animals, killing life in rivers and contaminating soil. At least nine people died and 122 people were injured. The chemicals extinguished all life in the 100 km (62 mi) long Marcal River.
On October 7, 2010, the red mud reached the Danube River, prompting countries, such as Slovakia, Croatia, Serbia, Romania, Bulgaria and Ukraine to develop emergency plans in response. The Danube is Europe’s second longest river. It is notable for being classified as an international waterway. On October 11, the Hungarian government announced that the managing director of the company involved with the disaster had been arrested, to be charged with “criminal negligence leading to a public catastrophe.” After the spill, emergency teams began pouring plaster and acetic acid (vinegar) into the Raba-Danube meeting point to lower the pH value.
After a government inquest, the Hungarian Prime Minister Viktor Orbán released a statement that indicated the cause of the spill was, presumably, human error. The Hungarian government has also said that the mud is “not poisonous” to humans. It has been suggested that the heavy metal concentrations are not continuing to impact the environment. On the hierarchy of industrial wastes, red mud is not as toxic as most. However, recent studies of the soil have indicated that a high level of salt in the ground is negatively impacting plant life. The ecological disaster remains one of the worst in the history of Hungary. Following the accident, a second dam was build directly behind the original to prevent the weakened wall from a complete failure.