Chapter 2: Industrial Processing
The coal is washed and treated before it is transported for commercial distribution. The excess water left over from this process, called coal slurry or coal sludge, is stored in open impoundments. Coal sludge is a mix of water, coal dust, clay and toxic chemicals such as arsenic mercury, lead, copper, and chromium.
In the mining sector, water is also used to cool or lubricate cutting and drilling equipment for dust suppression, fuel processing and revegetation when the extraction process is complete. Estimates of water used for coal mining vary from 1 to 6 gallons per million British thermal units (MMBtu), depending on the source of the coal.
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