Solution Overview

Water is a critical resource to sustain economic activities, development, and life. “The biggest threat to a sustainable water supply in South Africa is not a lack of storage but the contamination of available water resources through pollution” (Claassen, 2010). Acid mine drainage (AMD) is recognised globally as one of the most challenging environmental problems in the mining industry (Moodley, et al., 2018). AMD refers to the outflow of acidic water from a mining site. The coal and gold mines in South Africa are no exception with emerging literature indicating that the water decanting from mining activities is highly acidic and as such not suitable for drinking, natural watercourse, and agricultural purposes (Ochieng, et al., 2010). These limitations significantly influence livelihood and the ecosystems in mining communities if left untreated. It also necessitates research and applications globally on various forms of water treatment and prevention to mitigate or neutralise the acid levels of the mine water.   The resultant impacts of acid levels in mine water are evident in Africa particularly in the Southern African Development Community (SADC) region with high water restriction levels. The mining industries are requiring large quantities of water, which facilitates additional stress on this scarce resource in South Africa. By applying a waste metallurgical by-product to remove heavy metals from the raw acid mine water, combined with the application of a mobile water treatment plant, this project will treat a million litres of contaminated water a day, providing potable water for drinking and agricultural purposes in order to sustain food security. The proposed solution will enable demonstration of the technology at different sites, simultaneously optimising the wastewater treatment value chain that includes purification and reuse of the contaminated water. Furthermore, the fabrication of the mobile units would also support the local manufacturing industry and create a value chain that enables job creation.  

Technical Overview

The proposed solution aims to translate the current 20,000 litres per day pilot plant, into an integrated modular solution for gold and coal mining companies to purify acidic water for drinking and agricultural purposes. The first step is the purification process, which involves the use of a waste metallurgical by-product that is cost-effective and removes heavy metals from the raw acid mine water. The second step is the water softening phase and the last step involves the pumping of the partially treated water into the Reverse Osmosis membrane where water is demineralized or deionized by pushing it under pressure through a permeable membrane. This step is executed to remove ions and unwanted molecules from the water and makes it safe for human consumption. The process was successfully demonstrated, supported through collaboration with the University of Johannesburg and the Council for Scientific and Industrial Research (CSIR). A mineralogy analysis was conducted on the residual slag which revealed that minerals such as gypsum, magnetite, and synthetic lime can be recovered and be sold. Therefore, the technology recovers water by using a waste by-product and simultaneously transforms the waste by-product into saleable minerals.