Hungary yesterday declared a state of emergency in three of its 19 counties after the catastrophic release on Monday of at least 700,000 cubic metres of toxic sludge from a containment basin at the Ajkai Timfoldgyar Zrt aluminium plant near Ajka, around hundred kilometres southwest of Budapest.
At least four people died and at least 120 were injured. The government ordered evacuation of hundreds of residents of the seven hardest-hit villages.
The torrent is currently heading towards the river Danube where environmentalists fear it may cause an unprecedented ecological disaster. What makes the situation worse is that many rivers in the region are flooding because of unusually high rainfall in the last few days.
Yana Balling spoke with Rainer Wennrich of Germany’s National Centre for Environmental Research in Leipzig about what ecological impacts might be expected and decontamination strategies that could be undertaken.
How does the sludge get produced and how could it escape?
When aluminium is extracted from bauxite via the so-called Bayer process, red sludge forms as a by-product. The sludge is normally kept in large reservoirs where its fluid and solid components separate into water and mud.
What caused the accident is yet unclear, but it is likely that heavy rain has caused the dam containing the reservoir to break.
It is also possible that the reservoir was just not large or strong enough to hold the sludge it was filled with.
What is the chemical composition of the sludge?
It contains mainly FLUORIDE, sulphate and aluminate, but also chrome, nickel, manganese and heavy metals such as lead. Its arsenic concentration is at least a hundred times above the allowed threshold for drinking water.
How might contact with the toxic sludge affect human health?
The most dangerous thing about the stuff is that it is – to put it simply – a dilute solution of sodium hydroxide with an extremely alkaline pH value, between 11 and 12. This means it cauterizes eyes and skin, and attacks the lung when moist aerosols are inhaled.
Have similar chemical accidents happened in the past?
Ten years ago, large amounts of cyanide and heavy metals escaped from the waste reservoir of a Rumanian gold mine, contaminating rivers, including the Danube, and killing large quantities of fish. A similar disaster, also connected to ore processing, happened in 1998 in Spain when the waste reservoir at the Los Frailes mine ruptured and 5 million cubic meters of contaminated water rushed into the Guadiamar River near Seville.
What happens if the toxic waste reaches the Danube?
If the sludge enters the Danube, both human health and the environment will be affected in many ways. The more concentrated the toxic substances are, the more severe will be the impacts. Mass mortality will likely affect fish in the most heavily-polluted rivers close to the disaster site. The long-term consequences on humans, wildlife and the environment at large are still unclear.
The sludge will gradually dilute in the water, a process which will mitigate the negative effects. On the other hand, dilution will spread the toxic material over a large area, particularly if there is more rain and flooding.
Is it possible to contain or decontaminate the sludge?
It would be extremely difficult to prevent the sludge from entering the Danube. The main problem is the large size of the already contaminated area.
Emergency services are attempting to neutralize the sludge by pouring plaster into contaminated rivers but the effect will probably be minor
Image: A soldier prepares to help clean up a contaminated street
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