Water pollution is one of the most harmful legacies of South Africa’s mining industry. The oxidation of sulphide minerals in waste rock and tailings dumps relases acid, metals and sulphate into the water, creating acid rock drainage (ARD). There are thousands of impacted sites across the country and treatment by conventional methods are often not technically or economically viable.
TMG, with collaborating partners at UCT and Wits, has led research into the development of more sustainable, low-tech options to treat mining-impacted water. The focus of the work has been on developing a sound understanding of the chemical and biological processes that control the conversion of sulphate to sulphide and the subsequent conversion of sulphide to elemental sulphur. The fundamental knowledge underpinned the design and optimisation of a semi-passive process that does not require expensive reactor units or active energy inputs.
A guiding principal behind the work was to design a process that could be maintained by local communities, who would otherwise be negatively impacted by the polluted water. While the process would not produce potable quality water it could convert polluted minewater to a resource suitable for small-scale agriculture, with the recovery of a bio-sulphur product that has value as a soil conditioner, particularly in regions where agricultural land is sulphur-deficient.
Proof of concept has been demonstrated at laboratory scale and aspects of the process are being evaluated at pilot scale.