Use of alkaline mine waste as treatment for acid drainage

The environmental impact of industrial drainages on South Africa affects surface-and groundwater in a country already stricken by the extreme scarcity of water resources. Ba-Phalaborwa municipality of Limpopo province is a clear example of this environmental impact. There is an industrial area, with two mines and a fertilizer industry, allocated between the town and Kruger National park. In this study, several options have been researched to improve the environmental impact of that area and to reduce the risk of environmental damage to Kruger National park. The main aim of this experimental study was to investigate the possibility of treating the extremely acidic drainage produced in this area with the alkaline rocks (mainly carbonatite) disposed in the waste rock dumps and tailings of the mines. Thus, the quality of their water would be improved and, at the same time, the volume of the waste rock dump and/or tailings material within the mine facilities will be reduced. The experiments showed a clear improvement of the acidic water with the carbonatite from dump: pH increased from 1.4 to 4.3; total dissolved solids (TDS), electrical conductivity (EC) and salinity (Sal) decreased up to 68%, sulfate dropped 28%, total iron decreased 99.6%. The experiments with tailing material showed similar results; TDS, EC and Sal decreased between 51 and 65% and total iron was 96% removed. The main difference between the treatment with dump and with tailing is about the sulphate; the tailing removed up to 53.4% of sulfate, which is 30% more than the removal produced by waste rock dump. This is the first study about using carbonatite as a water treatment. The results obtained from the batch experiments encourage a deep study about the use of this mine waste in a future treatment plant.