Ultrafiltration membrane technology will be used at a new water treatment plant for minerals exploration and devel- opment company African Minerals’ Tonkolili iron-ore mine, in Sierra Leone, West Africa, reports water treatment engineering company Süd-Chemie – a Clariant Group company.
This new technology is an alternative to traditional sand filtration, says technical design and sales engineer Trevor Carruthers.
“Ultrafiltration makes use of consecutive layers of membranes supported over hollow plastic tubes. These systems filter down to a diameter of 0.3 µm, which is much smaller than that used by sand filtration technology, and enables the removal of bacteria and other impurities down to macromolecular level,” he explains.
The main advantage of this technology is that, unlike sand filtration, bacteria and viruses are removed and higher dosages of disinfectants do not have to be added to water, improving its quality.
The water quality produced by the ultrafiltration treatment process is 100% consistent with the standards for potable water specified by the Department of Water Affiars as the minerals are not removed from the water and it, therefore, retains the desired health benefits, Carruthers adds.
Further, an ultrafiltration unit has a smaller footprint than that of traditional sand filtra-tion plants. These systems are more compact and may be containerised for ease of transport.
Süd-Chemie is involved in providing potable water plants, which are used in mining villages and contractor camps to provide water for drinking and the flushing of toilets. “These are usually installed in the construction phase of mining projects, but many of these plants are used permanently,” says head of industrial sales Dries Lategan.
A potable water plant usually comprises combinations of filtration, flocculation and chlorination.
Süd-Chemie has also just completed work on two water treatment plants for iron-ore miner London Mining’s 100%-owned Marampa mine, in Sierra Leone.
The Marampa mine includes a 319 km² exploration licence that borders the Marampa mining lease, which was mined extensively between 1933 and 1975 by the Development Corporation of Sierra Leone. The property was acquired by London Mining in 2006.
“Direct flocculation and filtration technol-ogy was used at both the Marampa plants to produce potable water,” Carruthers says.
Further, the company finished installing three drinking-water plants as well as a sew-age plant for Canadian mining company Nevsun Resources’ Bisha mine, in Eritrea, at the start of this year, says Süd-Chemie head of engineering services for the Middle East and Africa Etienne le Roux.
Bisha is a large precious and base metals volcanogenic site with a massive sulphide deposit that went into commercial gold/silver production in February 2011.
“The Bisha mine was a particularly difficult site as summer temperatures can reach up to 50 °C, while winter temperatures average between 30 °C and 40 °C,” he adds.
Meanwhile, the company is currently in the process of constructing a new stripping plant for gold producer Newmont Corporation’s subsidiary, Newmont Golden Ridge, in Ghana.
Stripping water plants are usually found at heap-leach plants, where water needs to be clean enough not to block spraynozzles. Various processes can be used to treat the water, depending on its use.
“We’ve had an ongoing relationship with Newmont over the past seven years,” says Le Roux.
Süd-Chemie also recently built a water treatment plant, performed a chemical boil- out and cleaned the oil circuit of the turbines, for copper and gold producer Freeport McMoRan’s 56%-owned Tenke Fungurume copper mine, in Katanga province, in the Democratic Republic of Congo.
Tenke Fungurume includes three consec-utive openpit copper/cobalt mines, and is undergoing an $850-million Phase 2 expan-sion, which includes optimisation of the current facilities, and increasing mining and processing capacities.
As part of the second phase, Tenke Fungurume plans to expand the mill rate to 14 000 t/d of ore and to construct related pro- cessing facilities that would target the addition of about 68 000 t/y copper cathode production.
The expansion is targeted for completion in 2013. Based on the completion of these enhancements, Tenke Fungurume estimates yearly copper production will increase from 132 000 t of copper in 2012 to about 195 000 t.
“Süd-Chemie’s involvement at the mine was quite significant as it supplied water to the mining village as well as for the industrial equipment,” Carruthers points out.
Süd-Chemie also designs and installs water treatment plants according to require-ment. “For example, we have installed a water treatment solution for the sulphuric acid plant at Uranium miner Paladin Energy’s Kayelekera mine, in Malawi,” says Le Roux.
The mine is located in northern Malawi, 8 km south of the road connecting the town-ships of Chitipa and Karonga. The project has proven reserves of 2.8-million tons of contained uranium oxide.
The company also does the total on-site water management for platinum-group-metals producer Impala Platinum’s Rustenburg refrigeration plants, compressor and proces-sing plants and sewage units. “We treat what- ever water is used industrially at these mines,” says Lategan.
When a mine uses a refrigeration system, the water used in the system has to be treated to prevent corrosion, scale deposits and bacteriological proliferation, Bruce Schröder of Süd-Chemie technical services explains.
At many water processing plants, combina-tions of filtering, softening, demineralisation and reverse osmosis followed by disinfection are used to condition poor-quality water, he says.