Limestone Neutralization of Dilute Acid Waste Waters.
U S Pat 3 617 560 1971 Nov; :
A method is described whereby dilute pickling, chemical processing, and mine drainage waters can be efficiently neutralized with limestone with particle sizes of 1-10 micrometers. A limestone slurry of 1-10 micrometer particles is prepared by passing a fraction of the acid waste water through the limestone grinder and then mixing this slurry with the remaining portion of the stream. Precipitation with this slurry is very rapid (<5 s), increasing the plant neutralizing capacity by 300-600 pct. The neutralized effluent is aerated to strip co2 and to oxidize the fe2+ and is then passed through a clarifier prior to discharge.
U.S. Pat. 3,617,560; Nov. 2, 1971; Chem. Abstr. 76:27,831C