The Use of Passive Treatment Systems To Remediate AMD From Abandoned Coal Mines, EMalahleni, South Africa - Column Experiments
Dube, Mpule Gloria (1); Ramasenya, Koena (1); Van Zweel, Nicolaus (2)
1: council for geoscience, South Africa; 2: North West University, Potchefstroom Campus, Centre for water science and management
Acid mine drainage (AMD) production from abandoned coal mines is a world-wide environmental problem. Characteristics of AMD includes low pH (<4), high sulfate (SO4) concentrations, high acidity levels and potentially hazardous chemical constituents such as As, U, Cu, Al, Fe, Mn etc. Passive treatment technologies for AMD remediation can function in remote areas with low costs of operation, monitoring and maintenance and therefore are practical for setting up on abandoned mine sites. Even though such systems have been used to treat acid mine water efficiently, limitations such as coating and clogging as a result of Al3+ and Fe3+ oxyhydroxide precipitates have been reported.
For solving the clogging problems associated with most of the passive treatments, dispersed alkaline substrate (DAS) was introduced. Column experiments of a DAS and reducing and alkalinity producing system (RAPS) were staged in the laboratory for the treatment of net acidic mine water from an abandoned coal mine situated in Mpumalanga Province of South Africa. DAS is a system composed of coarse matrix mixed with a fine grained alkaline material. The main aim of the study was to investigate the effectiveness of the DAS system in treating AMD compared to the traditional RAPS.
For performance assessment of the system, water parameters such as pH, Redox, total dissolved solids (TDS), concentrations of metals and metalloids were analysed weekly. Both treatment systems were able to raise the pH from an average of 3 to 8. Contaminants such as Fe, Al, and Zn were removed below detection limit. However, there was limited removal of Mn and its concentration was found to be above the required water quality standard limit. The column experiments remediated acid water successfully for 21 weeks after which the DAS system clogged while RAPS was continuing to treat AMD successfully.