Treatment of acid mine drainage water at the Blaauwkraanz South discard facility

The Blaauwkraanz Mineral Residue Facility (MRF) is a coal discards facility designed to accommodate coarse and fine coal discards from the Navigation Coal Processing Plant in South Africa. The Southern extension of the MRF was operated from 1992 and decommissioned in 2012 due to less-than-acceptable safety factors. The MRF was designed with a concrete penstock to decant supernatant water from the slurry pool. The penstock was also decommissioned. The supernatant water in the dormant slurry compartment became impacted by the coarse discards and became highly acidic and concentrated with heavy minerals, making it unsustainable for the site to treat within the available water treatment plants. The water was then managed through pumping from the seepage collection compartments to the top of the slurry compartment and allowed to seep through the MRF. This created a heap leach effect that further concentrated the salts and heavy metals in the water. An engineering capability study and test work was conducted on-site to evaluate the treatment capabilities and potential management options for the toe-seepage. Through this study, the site was able to optimise the operation of the existing water treatment plants to cumulatively treat more than 100 ML of the highly acidic water.