Optimising the Rehabilitation of polluted Mine Tailings and Water by SupaZorb

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Courtesy of SupaZOrb

To date the polluted acid mine drainage (AMD) – the second biggest environmental problem of the world - from South Africa’s gold mines, was characterised and treated by the precipitation of heavy metals with lime and sulphates, by means of iron exchange. The chemical treatment with expensive and toxic caustic soda (Sodium Hydroxide, NaOH) is to lift the pH, in order to reduce the corrosion on pipes and pumps. The use of lime (Calcium Carbonate, CaO), is to lower the pH for the precipitation of metals and some residues still accumulating in the cleaned water. This water then dispersed into the wetlands to get naturally rehabilitated by the organic material within the wetland system and finally it migrates to the ground water table. This would have been historically acceptable in low volumes of water.

The research of optimising the rehabilitation of polluted mine tailings and water by SupaZorb is divided into different phases for an environmentally friendly and a fully closed cycle of rehabilitation.

Under field conditions the AMD was filtered over a test bed of cascades filled up with different materials. Firstly the first cascade was filled with SupaZorb, the second cascade was filled only with pine-bark and the third with Casuarina – both mixed with sand by 50% of weight. Finally the AMD passed a cascade of Dolomite, a sedimentary rock. With this test arrangement it was also possible to see which material is most suitable under different, natural conditions. The difference to the lab conditions is that not all the natural climatic changes and other factors, like wind and rain, could be duplicated in the lab, but under field conditions these changing natural circumstances influenced the results. After a period of only a few months the treatment system of SupaZorb – as the only non-chemical treatment method in the world – proved, to be a cheaper and more effective treatment of AMD, compared to all the other current, treatment systems. Different test procedures from laboratory tests on AMD, dolomite stones, dried material of used SupaZorb from treatment bags and dried loose used SupaZorb, showed the long term potential and sustainability of removing metals from AMD.

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