The worst of all possible scenarios for the Danube might not come to pass, but cleaning up after the sludge spill in Hungary will still be a years-long process. Since the failure of a reservoir just over a week ago released toxic material from an aluminum plant, the focus has been on evacuating nearby towns and on building an emergency dam to prevent more sludge from escaping if another wall—which is already showing cracks—should fail.
The long-term question, though, is the water-quality implications for the areas affected by the sludge. Although the company hasn’t revealed the exact composition of the sludge, by-products from aluminum processing typically contain cyanide, cadmium, and chromium. The sludge is highly alkaline, causing burns in many who came into contact with it—at least eight people died and more than 100 have been injured. As of Monday, however, the pH of the Danube downstream of where the sludge entered was measured at a slightly-higher-than-normal 8.5, which officials said was not high enough to kill aquatic life.
We’ve faced a similar situation in the US, though on a smaller scale, when a dam in Tennessee broke in December 2008, releasing tons of sludge containing fly ash and sending it toward the Emory River. In Tennessee then, as in Hungary now, a big concern is what happens when the sludge dries and the fine, potentially toxic dust left behind becomes airborne. In Tennessee, liquid dust suppressants, straw, and other materials were applied to many areas to try to contain the dust. In Hungary, crews are trying to dilute it by washing it away where it accumulates—spreading the material further, but reducing its concentration. In some places in Hungary, in an attempt to reduce the alkalinity of the sludge, substances like fertilizer and plaster have been poured onto it. Workers, who were already wearing hazardous material suits to deal with the caustic substance, are now wearing masks as protection against the dust.
Testing in the weeks and months to come will determine the extent of the environmental damage in Hungary—as well as in the countries downstream, Croatia, Serbia, Bulgaria, Romania, and the Ukraine.