A South African titanium mine is about to create a safer living environment and mitigate its environmental impact by focusing on reusing water from its tailings dam. The developments are the result of Dutch and South African collaboration and could prove a solution for other mines struggling with the same challenges.
To understand the challenges of tailings dams, it is important to understand the mining operations. A titanium mine in Kwazulu Natal uses hydraulic ejectors (water cannons) to flush metalliferous sand from the dunes. The slurry gets split into three streams: 1) the heavy minerals concentrate that they are after 2) sand; and 3) a residue we call tailings; a very fine, thin mud consisting of small particles, sediment and water.
While the mineral concentrate gets transported via road to a smelter complex and processed into a wide array of useful products (think of titanium for airplanes, the health sector or even everyday products like paint) and while the sand is used to rebuild the dunes, it’s the tailings that proof a challenge: this waste product currently gets deposited in an artificial lake of about 4km long and 2 km wide.
Besides needing a tremendously large lake and a strong enough dam to contain the volume of tailings, tailings also provide a long-term risk: if one would just leave the tailings dam unused, a crust will form on top, which may look strong enough to walk on, or even built houses on, but is unreliable and can break, potentially resulting in harmful disasters.
It may sound obvious: the tailings still contain an enormous amount of water and extracting this water would solve a lot of the challenges. This is exactly where Dutch engineering company Hencon focusses on. Together they are working on a technique to separate the water from the sediments, using Dutch techniques based on the amphirol – a screw propelled vehicle, invented by the Dutch in the fifties.
Not only will it reduce the volume of the tailings (and thus, the need of such a big lake to store the tailings), it will also increase the density of the tailings substance, lowering the risk of crust breaking. But above all: the mine’s waste water can be reused for the core operations, leading to a substantial reduction in water usage, something that is a hot issue anywhere in the world.