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RECOVERY OF LIME AND MAGNESIUM IN POTABLE WATER TREATMENT
Citation:
Thompson, C. AND G. Mooney. RECOVERY OF LIME AND MAGNESIUM IN POTABLE WATER TREATMENT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-76/285.
Description:
A hard, turbid surface water was successfully treated using the magnesium carbonate process in a 2 mgd pilot plant at the treatment works of Water District No. 1 of Johnson County, Kansas, for one year during 1975 and 1976. During this study, froth flotation was used to separate river sediments from calcium carbonate formed in the treatment process. Both bench-scale and pilot plant flotation tests have shown that sludges formed by softening turbid waters can be processed to yield a relatively pure calcium carbonate suitable for lime recovery. Prior to this work lime sludge from surface water treatment had not been useable for lime reclamation. Process variables affecting both magnesium carbonate recovery and calcium carbonate beneficiation were studied in this work. Magnesium carbonate was successfully produced on a continuous pilot scale from recycled magnesium bicarbonate liquor. Process economics were favorable. A comparison of capital and operating costs for magnesium carbonate treatment, sludge flotation and lime recovery with present operating costs, including waste disposal, indicated that annual costs would be lower with the new technology.