Liquid purification or separation – With gas-liquid surface contact means
Reexamination Certificate
2000-04-07
2001-12-04
Upton, Christopher (Department: 1724)
Liquid purification or separation
With gas-liquid surface contact means
C210S170050, C210S206000, C210S912000, C210S615000
Reexamination Certificate
active
06325923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for the in situ treatment of acid mine drainage water or acidic drainage water from mine tailings in order to remove dissolved heavy metal ions and sulfate ions therefrom, and more specifically to a method and apparatus for the foregoing purpose utilizing sulfate reducing bacteria.
2. Statement of the Prior Art
Water flowing from mines percolates through tailings piles, and in the presence of oxygen from the air reacts with the metal sulfides contained in the tailings, such as iron pyrites or iron sulfides, forming soluble metal sulfates and sulfuric acid in the water stream leaving the mine tailings.
The use of sulfate reducing bacteria for producing hydrogen sulfide from a solution containing sulfate ions and metal ions, and the subsequent reaction of the hydrogen sulfide with the metal ions to remove the metal ions from the solution as solid metal sulfides, is an old and well-known process. See U.S. Pat. No. 5,587,079, issued Dec. 24, 1996, to M. V. Rowley, for “Process for Treating Solutions Containing Sulfate and Metal Ions.” The chemical reactions involved in the process are described in detail in the Rowley et al. patent. The Rowley et al. patent describes and shows a bioreactor using sulfate reducing bacteria to convert sulfate ions to sulfide ions which in turn react with heavy metals ions in an aqueous solution to produce solid metal sulfides.
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an improved bioreactor for reacting sulfate reducing bacteria with heavy metal sulfates and sulfuric acid contained in aqueous solutions such as in acidic aqueous drainage from mines and mine tailings, in order to convert the sulfates to sulfides and produced heavy metal sulfide precipitates, and thereby produce water of substantially reduced heavy metal and sulfate content.
Another object of the present invention to provide a bioreactor of the foregoing character having an improved water permeable bacteria and bacteria nutrient containing structure.
A further object of the present invention is to provide an improved bacteria nutrient containing structure for a bioreactor that reduces settling and packing of the bacteria nutrient medium and enhances contact time of water with the nutrient medium.
SUMMARY OF THE INVENTION
A bioreactor embodying the present invention is formed by an elongated horizontal trough of concrete or half culvert of corrugated steel supported on concrete pads or cradles positioned in ground soil above or below ground level and downstream of a mine drainage collection pond in which aqueous acidic mine drainage containing dissolved heavy metal sulfates and sulfuric acid is collected.
The reactor includes an inlet section in which sulfate reducing bacteria and nutrients therefore, such as cow manure, are supported. The inlet section may also contain other reactants such as limestone for increasing the pH of the drainage solution in order to promote bacterial activity. The bacterial and nutrient materials are retained in the cells of honeycomb panels arranged at an angle with the trough so that the honeycomb cells of adjoining or juxtaposed panels are offset from cells of adjacent panels in order to form a tortuous path for the flow of acid mine drainage solution therethrough.
Mine drainage water with entrained bacteria and nutrients and at the desired pH flows to the outlet or reaction section wherein the bacteria reduce the sulfates in the mine drainage solution to produce hydrogen sulfide which in turn reacts with the heavy metal ions in the solution to form heavy metal sulfide precipitates. The reaction section is a packed bed, rounded river rocks or cobbles being used as packing. The sulfides are deposited on the rocks or cobbles in the trough or washed through and collected in a downstream collection pond. Eventually the sulfide build-up may necessitate the removal and replacement of the cobbles.
The troughs are formed of any appropriate material in any desired cross-sectional configuration and length. One form of trough is constructed of reinforced concrete and is a truncated V-shape in cross-section defining inwardly sloping side walls and a bottom wall or floor. End walls define the ends of the trough or channel. Another form of trough is a long metal culvert hemispherical in cross-section and supported on concrete pads.
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Manchester Kenneth R.
Zaluski Marek H.
Crandell Ralph F.
MSE Technology Applications, Inc.
Upton Christopher
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