Treatment of abandoned coal mine discharged waters using lime wastes

We evaluated the feasibility using waste lime for reclaiming abandoned coal mines. For this evaluation, lime wastes were reused in neutralizing coal wastes in a field experiment. In runoff and leachate, pH and heavy metals were monitored for approximately 4 months to evaluate ecotoxicity at the remediation site. When the amount of added lime cake was equivalent to the 100% lime requirement for neutralization, stable neutralization was obtained during the entire experimental period. Because of pH neutralization, ecotoxic heavy metals were efficiently contained in the coal waste pile. When smaller amounts of lime cake were applied, although heavy metal releases did not increase, the pH in runoff/ leachate fluctuated depending on the amount of precipitation and the history of field treatment. This suggests that field specific environmental factors have to be considered in determining the amount of lime cake required for stable neutralization. These findings from the field study demostrated the potential use of lime waste from soda ash production for reclaming abandoned coal mines.