Toxic Spill In Hungary Kills Four

An open reservoir used to store toxic alumina-refining slurry breached on Oct. 4 near Ajka, Hungary, flooding the countryside with an estimated 1 million m³ (roughly 5 million 55-gal drums) of pH 13 sludge that has killed at least four people and seriously harmed hundreds of residents, wildlife, and the environment. The Hungarian government has declared a state of emergency as the toxic red mud, facilitated by heavy rains and flooding, traveled to the Danube River.

The Ajkai Timfoldgyar Zrt refinery, where the catastrophe occurred, is owned by MAL Magyar Alumínium, which sells chemical-grade alumina for use in zeolites, glasses, ceramics, and other products used in the chemical industry, according to the company’s website.

Alumina is typically extracted from bauxite ore using sodium hydroxide. For every 1 ton of alumina extracted, approximately 2 tons of highly alkaline red slurry is produced, the color of which comes from iron oxide, says Chris Bayliss of the International Aluminium Insitute.

Normally, the slurry contains heavy metals and “whatever else is found in the rock besides alumina, which can include copper, zinc, arsenic, and sometimes radioactive elements,” explains Karen Hudson-Edwards, an environmental geochemist and mineralogist at the University of London, Birkbeck.

Most refiners allow the tailings to settle in reservoirs open to the environment until the sodium hydroxide separates from the sludge and can be recovered for future refining or neutralized, Bayliss says.

When the MAL Magyar Alumínium tailings reservoir sludge—containing extremely high levels of sodium hydroxide and low levels of radioactivity—poured through several towns, it affected an area of 40 km² (more than 15 sq miles), says Csaba Csendes, an official at Hungary’s National Directorate General for Disaster Management. “There won’t be vegetation in the area for quite a long time,” he tells C&EN.

In a statement, MAL Magyar Alumínium notes that, according to European Union policies, “red mud is not a dangerous waste.” The company also asserts that it could not have predicted nor been able to avert the catastrophe.

According to a Greenpeace statement, Hungary has “two other such refineries with an estimated 50 million m³ of similarly toxic red mud in highly sensitive areas close to rivers,” posing a threat to wildlife, wetlands, and safe drinking water.

In the past 40 years, at least 59 major failures of dams on refining slurry reservoirs have occurred worldwide, Hudson-Edwards notes. She says many of the failures have resulted in long-term damage to ecosystems, significant impact on nearby communities, and the loss of nearly 700 lives. For example, in 2000, a tailings reservoir containing waste from Aurul’s gold mine in Baia Mare, Romania, released cyanide-containing wastewater into a major Hungarian river.