In deep mines, water can pose a great danger, undermining layers of rock and causing collapses and flooding, but other types of mining use water to great advantage. Sulphur, for example, can be mined in an unusual process using water. Three pipes of different sizes, one inside another, are drilled into the sulphur reserves. Then extremely hot water, under pressure, is pumped down the outer pipe. This melts the sulphur. Compressed air is then pumped down the central pipe, causing the melted sulphur to move up the middle pipe to the surface. This system was developed by an American engineer, Herman Frasch (1851-1914).
Mining water use is water used for the extraction of minerals that may be in the form of solids, such as coal, iron, sand, and gravel; liquids, such as crude petroleum; and gases, such as natural gas. The category includes quarrying, milling of mined materials, injection of water for secondary oil recovery or for unconventional oil and gas recovery (such as hydraulic fracturing), and other operations associated with mining activities. Dewatering is not reported as a mining withdrawal unless the water was used beneficially, such as dampening roads for dust control.
During some mining activities, particularly gold mining and dredging, water is used for sluicing and flushing out minerals. In most mining operations the majority of this water is recycled, so water loss from rivers and streams is minimised. Water take (abstraction) can be more pronounced where dredging occurs near the riverbed. Loss of water may reduce in stream habitat, elevate water temperatures, and increase summer algal blooms, which may affect invertebrate and mahinga kai communities.
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