A method for removing metals from metal-containing acidic mine wastewater uses a basic sludge produced by the method for treating the wastewater. The wastewater is mixed with a lime slurry and with the basic sludge. This mixture is allowed to separate into an aqueous effluent and an acidic sludge. The effluent is mixed with the lime slurry and with a composition containing an iron compound, to produce a mixture. This mixture is allowed to separate into an aqueous effluent and the basic sludge. Lignin derivatives, such as calcium lignosulfonate, may be included in the treatment mixture.
Description
BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a flow diagram showing a preferred embodiment of the process of the invention.
Claims
1. A method for removing metals from metal-containing acidic mine wastewater, in which a basic sludge produced by said method is used in treating said wastewater, comprising the steps of:
(a) mixing said wastewater with a lime slurry and with said basic sludge to form a mixture;(b) allowing said mixture to separate into an aqueous effluent and an acidic sludge;(c) mixing said effluent with a lime slurry and with a composition containing an iron compound, to produce a mixture; and(d) allowing said mixture of step (c) to separate into an aqueous effluent and said basic sludge.
2. A method according to claim 1 wherein said composition containing an iron compound comprises acidic sludge produced in step (b).
3. A method according to claim 1, further comprising, after step (b), the step of mixing the effluent of step (b) with lignin derivatives and using said mixture in step (c).
4. A method according to claim 2, further comprising, after step (b), the step of mixing the effluent of step (b) with lignin derivatives and using said mixture in step (c).
5. A method according to claim 1 wherein said composition containing an iron compound is a ferrous salt solution compound.
6. A method according to claim 1 wherein said composition containing an iron compound is a ferric salt solution.
7. A method according to claim 1 wherein said mixture of step (a) has a pH in the range of 4 to 6.
8. A method according to claim 1 wherein said mixture of step (a) has a pH in the range of 4.3 to 5.
9. A method according to claim 3 wherein said mixing with lignin derivatives is carried out under aeration.
10. A method according to claim 4 wherein said mixing with lignin derivatives is carried out under aeration.
11. A method according to claim 1 wherein said mixing with said lime slurry and said acidic sludge is carried out under aeration.
12. A method according to claim 2 wherein, the portion of said acidic sludge used in step (c) is in the range of 2-25 grams per liter of said effluent from step (b).
13. A method according to claim 2 wherein, the portion of said acidic sludge used in step (c) is in the range of 5-12 grams per liter of said effluent from step (b).
14. A method according to claim 3 wherein said lignin derivatives comprise calcium lignosulfonate.
15. A method according to claim 4 wherein said lignin derivatives comprise calcium lignosulfonate.
Patent Application
20070205159
