METHOD FOR TREATING ACID MINE DRAINAGE

摘要

A process for treating acid mine drainage containing heavy and base metals and soluble contaminants is provided. In one embodiment, at least a metal cation is added to the acid mine drainage at a pre-select pH to form insoluble heavy and base metal complexes. After the removal of the heavy and base metal complexes, the pH is raised to the alkaline range. Following removal of base metal hydroxides and gypsum, membrane filtration is employed to generate a treated membrane permeate having a reduced concentration of heavy and base metals and soluble contaminants, and a membrane reject stream containing a concentrated brine. The concentrated brine is further treated with additional lime and at least an aluminum salt to remove remaining soluble contaminants, thus producing a treated water stream with reduced levels of contaminants. Carbonation with CO2 is employed at the end of the process to neutralize flows and further precipitate residual aluminum and calcium salts.

主权项

1. A method for treating a discharge stream to reduce the concentration of metals and soluble contaminants, the discharge stream contains a concentration of soluble anionic species selected from sulfate, fluoride, and chloride, and one or more metal ions selected from aluminum (Al), antimony (Sb), molybdenum (Mo), vanadium (V), arsenic (As), copper (Cu), cadmium (Cd), cobalt (Co), lead (Pb), manganese (Mn), nickel (Ni), selenium (Se) and zinc (Zn), the method comprising:
contacting the discharge stream with a metal cation selected from divalent and trivalent metal cations and mixtures thereof, at a pre-select pH and in an amount effective for the metal cation to form at least an metal complex with one or more of the metals; performing a liquid solid separation to remove the metal complex forming a first effluent stream; adjusting the pH of the first effluent stream to a second pre-select pH to generate a first precipitate; performing a liquid solid separation to remove the first precipitate to generate a second effluent stream; passing the second effluent stream to a filtration device having at least a membrane element to generate a permeate stream and a reject stream supersaturated with calcium sulfate; performing a settling and a liquid solid separation step to remove at least a portion of the calcium sulfate, forming a supernatant having a reduced concentration of calcium sulfate; adding at least an aluminum salt to the supernatant for the soluble anionic species to react with the aluminum salt to form a second precipitate at an alkaline pH; performing a liquid solid separation to remove the second precipitate to form a third effluent.