7 Oct 2010

Briefing: Hungarian sludge flood

Briefing: Hungarian sludge flood - October 06, 2010
Posted on behalf of Yana Balling
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 in what appears to be the worst chemical accident in Hungary’s history, 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.

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