As tailings ( English ) refers to the mining fine-grained residues from the processing of ores , mostly in the form of sludge present. They are stored near the mines or processing plants, usually in large sedimentation basins or sludge ponds separated by dams .
Word origin and word usage
In American English , tailings are residues that can arise during processing such as grinding or distilling. It is a word formation in English tail ("tail"), whereby the "rear end" of the processing is meant where the residues occur. The term is mainly used in the context of processing ore. For example for red mud (English bauxite tailings or red sludge ), which is a residue from the extraction of bauxite .
In German, the foreign word tailings is used for residues from ore processing. Due to the strong environmental impact, it often appears in connection with yellow cake production in the context of uranium ore processing .
As in English, tailings is also a plural word in German . However , the plural s can be omitted within word compositions . For example, in addition to tailing basins , the word form tailing basin is also used with approximately the same frequency. In addition to tailings pond (German “tailings basin”), the word form tailing pond is also used in English .
Chemicals and resource consumption
The storage of tailings in settling basins is associated with a high environmental impact , since the sludge usually also contains toxic substances such as mercury and arsenic , which are used in ore processing or arise as by-products. Some of the toxic substances get from the sedimentation basins into the environment through wind and weather . In connection with acid formation in particular, there is a risk that the contaminated liquid will seep into the ground (see acid mine water ). Birds and other animals can suffer serious health damage when they drink from settling tanks. They also introduce pollutants into the food chain .
In addition, storage in settling basins, some of which take up many square kilometers, consumes natural areas and large amounts of water. Modern processing techniques offer the possibility of separating the solid particles from the sludge and storing them dry on the surface of the earth. Due to the associated recovery of the process water, the water and space requirements are enormously reduced and the environmental hazard is reduced.
- October 2010: Kolontár dam burst in Hungary with 10 fatalities
- August 2014: Mount Polley Dam burst in Canada
- November 2015: Bento Rodrigues dam burst in Brazil with 19 deaths
- January 2019: Brumadinho dam burst in Brazil with 259 confirmed fatalities, 11 other people are still missing (as of December 28, 2019)
Due to the dam breaches that have occurred up to now, high demands are placed on the design, construction and operation of the sedimentation basins.
Tailings in uranium mining
The processing of uranium ore also creates sludge-like residues called tailings . Their amount correlates directly with the mass of the ore processed, which is why many millions of tons of this low-level radioactive tailings are produced worldwide every year.
Despite the separation of the uranium, the tailings still contain most of the activity originally present in the rock . These are mainly the nuclides radium -226, radon -222 and lead -210. However, the specific activity per unit mass is low compared to many other low-level radioactive waste products. Immediate health damage is therefore not to be expected if stored properly.
The difficulty in storing the tailings is that the pollutants previously bound in the rock are now broken up and are on the surface of the earth. This makes them much more mobile and easier to get into the environment.
A disposal of the contents of the settling tank can be based on the dimensions of only locally. The example of the renovation of the former SDAG Wismut production facilities in Thuringia and Saxony shows how this is done. The risk of weather erosion has been eliminated by draining , covering and renaturing the tailings. Since it was not possible to seal below the tailings, the risk of radioactive substances seeping into the subsoil remains. Therefore, close-knit environmental controls and groundwater treatment are carried out.
- Nils Engelke, Robert Klug ( Flottweg Separation Technology): Always on top, despite "underground" decanters in mining. In: AT Mineral Processing Europe. 07-08 / 2018, ( online ).
- What are tailings? Their nature and production. In: tailings.info
- article on Tailings at-minerals.com, 2018
- tailing at collinsdictionary.com . See under American English Meaning 1 for the plural word tailings .
- tailing at thefreedictionary.com . See the information on the plural word tailings : Only the processing of ore and mining are mentioned here.
- What are tailings? Their nature and production tailings.info
- For further examples see the list in the English Wikipedia: List of tailings dam failures .
- Brumadinho: mais duas vítimas do rompimento da barragem da Vale são identificadas g1.globo.com, December 28, 2019.
- Jonas Houben: Uranium Mining and Enrichment. Greenpeace Aachen, November 25, 2015, accessed on March 18, 2019.
- Uranium Mining in Eastern Germany (Engl.) 
- State Directorate Saxony 
- The legacy of bismuth