This study investigated the feasibility oftreating an acidic mine discharge with coal combustionproducts (CCPs). The goal of this treatment was tocreate a highly alkaline buffering zone inside themine. This buffered region was designed to treat thegeneration of acidic mine water prior to its discharge;subsequently preventing the adverse environmentalimpacts associated with acid mine drainage (AMD). Thedemonstrated treatment method involved the injectionof 418 tons of CCP into an acidic (pH=4.3), floodedmine void. Once injected, alkalinity from the CCP wasimparted to the system, which neutralized the existingacid and increased the pH. With elevated pH levels,metal species precipitated within the mine ashydroxides and carbonates. Consequently, the AMDafter injection had an elevated pH, increasedalkalinity, and a reduced metal load. Injection of theCCP slurry was possible with equipment developed bythe petroleum industry. This technology allowed theCCP slurry to be injected with significant pressureand at a high rate. Theoretically, the high pressureand rate would improve dispersal within the void. Inaddition, the high pressure is advantageous infracturing or breaking-down obstructions to injection.Currently, the mine has achieved pseudo-equilibriumwith respect to pH and alkalinity, approximately 6.3and 150 ppm as CaCO_3, respectively. Iron levels inthe AMD have decreased from 200 ppm to 120 ppm,manganese (Mn) concentrations have decreased from 7ppm to 5 ppm, and aluminum (M) levels have decreasedfrom 6 to below detection limits (<1 ppm). Furthermonitoring will be needed to track the pH, alkalinity,and metals levels over time.
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