The minerals that do not float into the froth are referred to as the flotation tailings or flotation tails. These tailings may also be subjected to further stages of flotation to recover the valuable particles that did not float the first time. This is known as scavenging. The final tailings after scavenging are normally pumped for disposal as mine fill or to tailings disposal facilities for long-term storage.
http://en.wikipedia.org/wiki/Froth_flotation#Waste_water_tre...

...General Description of Ore Processing in a Conventional Copper Flotation Plant ..... is affected by the freezing of the tailings pond (Gillespie and others, 2004).
Tailings disposal began in 1923 following development of a differential flotation process capable of separating complex ore into lead, zinc, and iron concentrates. ... have been discharged since 1923 to ponds occupying 373 hectares of land.
This disposal option would create a large tailings pond (lake) with a very...
While tailings disposal in tailings ponds is still quite common...
...the recurring spills and failures of conventional tailings disposal pond dams...
http://tinyurl.com/lcswphp

...gypsum tailings disposal pond at Kimberley, British Columbia...
...Church Rock uranium mill tailings disposal pond breached its dam...
http://tinyurl.com/m59l8vx

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Note added at 16 hrs (2013-06-01 02:23:10 GMT)
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Pierwszy odnośnik miał być taki: http://en.wikipedia.org/wiki/Froth_flotation#Principle_of_op...

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Note added at 18 hrs (2013-06-01 04:06:11 GMT)
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Żelazny Most – największy w Europie zbiornik odpadów poflotacyjnych należący do KGHM Polska Miedź SA.
Informacje o zbiorniku:
Powierzchnia całkowita 1394 ha
Objętość całkowita 340 mln m³
Długość zapór składowiska 14,3 km
Wysokość zapór 20~45 m
Objętość wody zgromadzonej w akwenie 8 mln m³
Głębokość maksymalna 2,5 m
Zbiornik jest wciąż powiększany. Składowisko dysponuje możliwościami rozwoju pojemności do ponad 1,1 mld m³.
http://pl.wikipedia.org/wiki/Żelazny_Most_(zbiornik_odpadów)