The toxic red sludge that gushed from a Magyar Aluminum (MAL) storage pond in Hungary is a necessary byproduct of the Bayer Process, which is the method used for the entire 40 million tons of alumina produced annually. This alumina is further processed into aluminum alloys, which we then enjoy as bicycles.
Besides recycling, the primary source of aluminum is an aluminum ore called bauxite. This rock contains aluminum minerals in a mixture with iron oxides, clay, and even a little titanium dioxide. In the Bayer Process, bauxite ore is crushed and then washed in a pressure vessel with sodium hydroxide (NaOH) at 200°C. Sodium hydroxide — a very powerful caustic agent — dissolves the alumina.
The waste product is filtered out and is called “red mud” in the industry. The red coloration comes from the concentration of iron oxides. Before the advent of evil, anti-business environmental regulations in the 70s, bauxite processing factories dumped this nasty sludge into rivers and oceans and even straight onto the ground. These days, red mud is collected in open pits, where the mud can dry into a red clay. Land where red mud is dumped is lost forever to any kind of building or agriculture.
It was one of these open pits that failed at the Ajka alumina plant in Hungary on October 4, when a retaining dam failed spilling nearly 300 million gallons of red mud in a five foot tall wave that inundated Kolontár, Devecser, and other nearby villages.
The nastiness comes primarily from the high sodium oxide (Na2O) content of red mud. Much of the lye is recovered as part of alumina processing, but what remains is still very highly basic and kills plants, fish, and people and causes severe chemical burns. Authorities downstream of the spill are pumping vinegar into the river in an attempt to neutralize the base.
Besides the water, red mud is about 40% iron oxide. Besides the lye, what remains is unextracted aluminum oxide (10%), silicon dioxide (10%), calcium oxide (10%), and titanium dioxide (5%). Though there are elevated levels of heavy metals in the red sludge (chromium 660 mg/kg, arsenic 110 mg/kg and mercury 1.2 mg/kg according to Greenpeace funded soil analysis), the levels are not considered to be dangerous to the environment. The main danger is the very high pH and physical destructive power of a huge quantity of mud. The huge volume of sediment also kills water life.
So far, eight people are known to have been killed by the initial red sludge deluge. Over 150 people were injured, 45 remain in the hospital. 280 homes were damaged. Magyar Aluminum has offered €360 in compensation to each affected person, which is barely enough to buy a lousy aluminum bike.