Water security makes tailings dam technology a key hurdle for South Africa’s mining growth, writes Adriaan Meintjes.
South African mines are quickly beginning to realise that key decisions on new mining projects or expansions simply cannot be made until the question of water security is resolved. This puts the focus squarely on tailings storage facilities (TSFs), which is the largest consumer of water on most mines.
In water-scarce countries like South Africa, it is increasingly becoming necessary to direct our work towards the management of water as a scarce natural resource for security at mine level. Indeed, our efforts to help mining clients become ‘water wise’ have included technical studies, advice, and even enabling technologies — all contributing to greater water security.
It is therefore no surprise to us that, in recent years, our clients have engaged us at the initial stages of project conceptualisation and design, to help optimise the tailings dams with water security in mind.
Saving water from mine tailings
Water consumption on a tailings dam is a function of the interstitial storage (water held between the solid particles of fines), evaporation, and seepage. The relative significance of each can be estimated as follows: While interstitial storage amounts to between 25% and 35% of the tonnes processed, this means that there will be about 0.25–0.35 cubic metres of water ‘locked up’ in this way per tonne of tailings deposited on the TSF. Water lost through seepage could be as much as 0.1–0.35 cubic metres per tonne (depending on the nature of the tailings and the in situ foundation materials below the tailings dam), while the evaporation could be 0.15–0.45 cubic metres per tonne. In total, then, about 0.5–1 cubic metre of water per tonne of tailings is generally lost to the mine in conventional tailings dam designs.
