METHODS OF REDUCING CALCITE FORMATION AND SOLUBILIZED METALS FROM AQUEOUS EFFLUENT STREAMS
Method of reducing calcite formation from solubilized calcium forms in aqueous effluent streams, including the reduction or removal of solubilized forms of nickel, selenium, sulfate, and magnesium.
1 . A method comprising:
identifying an aqueous effluent stream containing solubilized forms of selenium, nickel, calcium, magnesium, sulfate, and bicarbonate, each present at an initial concentration;
contacting the aqueous effluent stream with a softening composition to provide a softened effluent stream, wherein the softened effluent stream comprises reduced concentrations of nickel, magnesium, and bicarbonate;
precipitating at least one of ettringite or hydrocalumite from the softened effluent stream to provide a precipitated effluent stream, wherein the precipitated effluent stream comprises reduced concentrations of selenium and sulfate; and
recarbonating the precipitated effluent stream to provide a recarbonated effluent, wherein the recarbonated effluent comprises a reduced concentration of calcium.
2 . The method of claim 1 , wherein the softening composition comprises lime.
3 . The method of claim 2 , wherein the softening composition comprises Ca(OH) 2 .
4 . The method of claim 1 , wherein the precipitating comprises contacting the softened effluent stream with lime and at least one aluminate.
5 . The method of claim 1 , wherein the precipitating comprises contacting the softened effluent stream with Ca(OH) 2 and NaAlO 2 .
6 . The method of claim 1 , wherein contacting the aqueous effluent stream with the softening composition converts the solubilized form of the bicarbonate into a less-soluble or insoluble form of a carbonate.
7 . The method of claim 1 , wherein the solubilized form of the bicarbonate comprises Ca(HCO 3 ) 2 .
8 . The method of claim 6 , wherein the less soluble or insoluble form of the carbonate comprises CaCO 3 .
9 . The method of claim, wherein the aqueous effluent stream has a pH of less than 10.0.
10 . The method of claim 9 , wherein the aqueous effluent stream has a pH of less than 9.0.
11 . The method of claim 10 , wherein the aqueous effluent stream has a pH of less than 8.0.
12 . The method of claim 1 , wherein the softened effluent stream has a pH of at least 10.0.
13 . The method of claim 12 , wherein the softened effluent stream has a pH of at least 11.0.
14 . The method of claim 1 , wherein the softened effluent stream has a pH of about 10.0 to about 11.0.
15 . The method of claim 1 , wherein the precipitated effluent stream has a pH of greater than 11.0.
16 . The method of claim 15 , wherein the precipitated effluent stream has a pH of at least 12.0.
17 . The method of claim 1 , wherein the precipitated effluent stream has a pH of about 11.0 to about 13.0.
18 . The method of claim 1 , wherein the initial concentration of selenium is at least 100 ppb.
19 . The method of claim 18 , wherein the initial concentration of selenium is at least 200 ppb.
20 . The method of claim 1 , wherein the initial concentration of selenium is about 150 to about 250 ppb.
21 - 75 . (canceled)