Review: Long-term sustainability in the management of acid mine drainage wastewaters – development of the Rhodes BioSURE Process
decanting of flooded gold mines threatens water supply on the Witwatersrand, South Africa, one of the most intensively mined areas in the world. Large volumes of acid mine drainage wastewaters will require treatment here for decades and possibly centuries. Appropriate treatment technology needs to meet technical, financial, environmental and social sustainable development criteria, with the costs of long-term treatment providing the initial decision gateway. This review details a bioprocess development in which the use of sewage sludge as the electron donor/carbon source for microbial sulphate reduction, and the wastewater treatment public utility as the operator, was investigated in meeting these requirements. A programme is reviewed that led from fundamental studies in microbial ecology, enzymology and mathematical process modelling, through pilot plant studies, to the construction and operation of a full-scale plant treating 10 M. mine water/day. It was shown, in what became known as the Rhodes BioSURE Process, that with careful regulation of the mine water and the sewage sludge dosing flow rates, sulphate levels could be reliably reduced to below 100 mg/., at hydraulic retention times as low as 12 h. Ancillary metal and sulphide removal unit operations are described, as well as investigations into socially sustainable use of treated mine waters.
Keywords: acid mine drainage, mine wastewater treatment, sewage sludge, sulphate removal, metal removal