An integrated bioprocess for Acid rock drainage (ard) remediation And renewable energy generation

South Africa is a water scarce country that is facing multiple challenges associated with the management of freshwater resources. These include increasingly unpredictable climatic conditions, a growing population and a significant increase in the number of people who have been provided with basic services. These challenges have highlighted the need to conserve existing water resources. Although considered an industry in decline by many, mining has historically been a cornerstone of the South African economy and remains a significant contributor to GDP and employment. Active mining operations and legacy sites have resulted in widespread environmental degradation and remain a substantial risk to surface and groundwater resources through the discharge of untreated or partially treated mining-impacted water. Gold and coal resources are often associated with sulphidic gangue minerals and the oxidation of these minerals gives rise to acid rock drainage, which is characterised by low pH, elevated metal concentrations and a high sulphate load. Coal mining may also give rise to circum-neutral impacted water, which is characterised by elevated sulphate concentrations. The discharge of high sulphate effluent into receiving water bodies has resulted in salinisation of water resources in Gauteng, Mpumalanga and Limpopo. Increased salinity can have a negative impact on the environment and increase the cost of treating water to potable quality. Mining-impacted water can be divided into two broad categories. These are mine drainage, which is primarily due to groundwater rebound and is pumped out of active mines or can decant from abandoned workings and rock drainage, which is primarily associated with runoff and leachate from surface impoundments. Mine drainage is typically high volume and can be characterised by particularly low pH and high metal and sulphate loading. It has traditionally been treated by active chemical and physical processes. There has been substantial investment in treatment facilities to deal with these discharges and South Africa boasts a number of treatment operations that represent global best practice. Rock drainage is typically characterised by smaller volumes and the number and location of many of the affected sites make them unattractive for tradition active remediation technologies, both from an economic and logistical perspective.