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Abstract

A method is disclosed for processing industrial waste waters and, in particular, blow down water from thermal electric plants. The water is processed to concentrate the salts contained therein and to obtain a concentrated brine which can then be passed to a thermal evaporator and/or solar evaporation ponds. The water is processed by the addition of magnesium hydroxide and carbon dioxide in amounts sufficient to precipitate the calcium as calcium carbonate, thereby obtaining a water reduced in calcium content and increased in magnesium content from the industrial waste water. The treated water is processed to recover a purified water from a brine, preferably by reverse osmosis. Calcium hydroxide is added to the brine generated by the reverse osmosis process in an amount sufficient to precipitate magnesium hydroxide therefrom which can be recycled to supply the magnesium hydroxide used in pre-treatment of the water prior to the reverse osmosis process. A clarified brine is recovered from the magnesium hydroxide precipitation step and may then be naturally or thermally evaporated to produce a saturated slurry of salt solids. This slurry can then be further reduced to dryness by solar evaporation.

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First Claim