Reuse of hard water
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This post was last edited by cdpulin on 2010-9-19 at 15:40. The water hardness after our company treats arsenic-containing acidic wastewater using the lime-iron salt method is very high, reaching 1700 mg/L as calculated based on calcium oxide. The main issue is calcium sulfate hardness; are there any good methods to deal with it? The cost is less than 3 yuan per cubic meter, and the calcium oxide level is below 150 mg/L.
This can be achieved by converting calcium sulfate into calcium carbonate, which is less soluble in water. Adding sodium bicarbonate, or using an excess of air, or introducing the exhaust gases emitted from chimneys, can significantly reduce the calcium ion content.
Agree with the view on the second floor: NaHCO3 + Ca(OH)2 + CaSO4 = 2CaCO3 (precipitate) + Na2SO4 + 2H2O