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
Water Sewage & Effluent March / April 2017 31