A Model for Prediction of Neutralizer Usage and Sludge Generation in the Treatment of Acid Mine Drainage from Abandoned Mines: Case Studies in Japan

Abstract

Acid mine drainage (AMD) from about 80 abandoned or closed mines in Japan are actively treated by neutralization; the government spends billions of yen every year to protect the environment from these discharges, and treatment will have to continue for many years. However, it is difficult to predict the future AMD chemistry, neutralizer requirements, and volume of sludge to establish future costs, chemical inputs, and wastes. The water monitoring data or source rock samples for conventional predictive methods are not available. In this study, a predictive model for AMD composition and the neutralization process was constructed based on geochemical modeling, assuming first order kinetics for the dissolution of several minerals. The solution composition, neutralizer requirements, and sludge generation were estimated for case studies at two abandoned mines in Japan: a sulfur mine, and a copper and iron mine. The model effectively predicted AMD composition after termination of mining and was also useful for estimating future neutralizer requirements and sludge volumes. This research will increase understanding of the lifecycle environmental costs in the mining industry.