ABB
Water desalination is increasingly becoming a viable water management solution for mining companies as pressures mount to be less reliant on fresh water supply.
Witwatersrand and is indicative of the value of collaboration between mining companies and government. In February 2017, the Minister of Water and Sanitation, Nomvula Mokonyane, officially launched the Eastern Basin’ s AMD plant: the third high-density sludge treatment plant in the province to deal with the legacy issue of acidic mine water.
The other two AMD plants, the Western Basin treatment facility in Krugersdorp and the Central Basin treatment facility in Germiston, have been operational for a few years.
Desalination – a global focus for miners’ water woes
Piesse says tight water supplies have increasingly led to mining companies investing in climate-independent sources of water, such as desalination.
Recently, the Chilean Copper Commission, Cochilco, issued a report predicting that seawater will account for 50 % of water used by the mining industry in Chile by 2026. Currently, it stands at 19 %.“ Desalination is definitely on the rise in mining, and some operators are even using raw seawater to process certain ores. Most modern desalination facilities use reverse osmosis,” said Laurie Reemeyer, founder and principal consultant of Resourceful Paths, in an interview with Barrick Gold.
However, desalination is an expensive and energy-intensive process.“ The main focus, therefore, in desalination is finding ways to do it with less energy, and make it more economic. In the last 10 years, there has been quite a lot of development in this area. The main innovation has been around pressure recovery devices, which have made the desalination process more efficient and affordable,” he says.
The costliest element of desalination, although many people are unaware of this, is the transport of the water to the mine, says Reemeyer.“ You may have a mine in the mountains of Chile, for example, located 150km from the sea. The cost of getting water to a site like that can run as high as USD3.00 per meter cubed, more than the cost of desalinating the water itself. So, the real questions are, can the volume of water used be reduced, can waterpumping systems be made more efficiently, and can mine processing facilities be built in locations that reduce the cost of pumping these alternative water sources?”
Potential for southern Africa’ s mining sector
The issue of transport raises critical questions, specifically for a country like South Africa that is blessed with an extensive coastline and abundant mineral reserves, which, unfortunately, do not overlap in geographic proximity.
Diversified mining company South32 reached a milestone in September 2016 when it opened a seawater desalination plant at its Hillside Aluminium Smelter in Richards Bay, capitalising on its closeness to the Indian Ocean. The plant is also a case in point about the value of partnerships.
“ In working with local government, we opened the R74-million desalination plant, demonstrating how sound relationships and the right partnership can create shared value. The plant not only ensures that our Hillside operation has adequate water supply, but it also has the capacity to supplement the municipal water supply in times of critical shortage. It has created jobs and contributed to skills development in the surrounding community,” said Mike Fraser, president and chief operating officer of South32’ s African region, during the indaba.
An older, similarly noteworthy project is that of Trekkopje, a large uranium project located in the Erongo desert region of Namibia, which runs a 54 000m 3 per day desalination plant allegedly the largest of its kind in southern Africa.
With the lack of ground- and surface water resources and the abundantly rich mineral reserves in the area, as well as the water intensive nature of mineral extraction, desalination was the only viable solution to support the development of the mine.
Designed, constructed, operated, and maintained by Aveng Water, the plant can deliver 20 million m 3 of water per year. The intake system draws seawater from the ocean, 1km offshore, and caters for a future potential water demand of 45 million m 3 per year. The treated seawater is pumped approximately 50km in an overland pipeline to the mining site, making the project viable from a financial perspective, again, because of proximity to the coastline.
International impetus on better water use
Technical interventions, such as desalination and treatment facilities, are not the only initiatives that mines are undertaking to be more water wise. Support also comes from international lobby and policy level. networking contributor tech news industry environment infrastructure municipalities
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