Scientific research and development organisation the Council for Scientific and Industrial Research (CSIR) has developed and patented two wastewater technologies.
One of these technologies purifies mine wastewater to a standard that is suitable for domestic, agricultural and industrial use; while the other recovers valuable minerals from municipal wastewater.
Acid mine water is a by-product of the mining and minerals industry. Mines ceased pumping water as resources, such as gold became depleted, resulting in water accumulating in the void and discharging into neighbouring mines and connecting underground tunnels. Active and abandoned mines discharge millions of megalitres of metalliferous and acidic drainage, laden with toxic and hazardous chemicals yearly, posing serious health risks to humans and other living organisms, the organisation indicates.
The magnesite, softeners, reverse osmosis and eutectic freeze process which purifies water to drinking quality and recovers valuable minerals from acid mine drainage is central to this innovation. Brine, a highly concentrated water solution of common salt resulting from this treatment process, is used to recover additional salts that have commercial value, such as sodium-based salts.
The first phase of the treatment chain recovers iron, which is useful in the paint- making industry, while the second phase recovers gypsum that can be used in the fertiliser industry and metallurgical processes. Phase three recovers limestone, which is used in a number of industrial applications. The second process, a struvite synthesis process, entails the attenuation of nitrates and phosphate from municipal wastewater effluent.
The robustness of the technology was improved at a CSIR pilot plant. The organisation is in discussions with government, mining houses and agencies about the uptake of the technology.
The CSIR has further designed a chemical-free water disinfection prototype plant, specifically for rural water supply purposes. The SafeWaterAfrica project is funded by the European Commission.
The CSIR and 11 partners from Europe and Africa are developing an autonomous water purification system using low-energy treatment technology.
The researchers have designed and built a prototype water treatment platform at the CSIR in Pretoria and are conducting experimental tests using the platform. The results from these tests will provide design input for the two demonstration systems to be built this year. The two demonstrators will be implemented at selected rural sites.
Unlike conventional methods that use chemicals and require extensive energy, the technology is based on a chemical-free water purification process that uses energy from renewable sources. The treatment plant uses a carbon-based electrode, which can be operated using solar energy, to remove organic and microbial pollutants from the drinking water sources.
The water treatment prototype consists of conventional pretreatment modules, a remote monitoring and control system and a solar power supply.
The system uses a number of commercially available sensors together with innovative algorithms to derive a multitude of water quality measures from the combined readings of these sensors.