The relationship between mining and water is a fragile and complicated one. Mines are either operating in areas with very limited water sources or areas with excessive water. These two conditions result in varying water management strategies and for the mines in drier areas the supply of process water becomes a critical factor. The water ‘issue’ that both regions face is the management of tailings. These two climate challenges as well as tailings are discussed further below.
Ultra-filtration (UF) with membranes
Pentair is a market leader for ultra-filtration (UF) with membranes. Our membranes are widely applied in the mining industry and are used in combination with conventional technologies as tertiary treatment, either for re-use or to meet ever-tightening discharge standards. With limited fresh water supplies, rising costs and restricting legislation concerning discharge, mining companies are looking for ways to decrease their water footprint.
A relatively new application for membranes is the so-called acid mine drainage process. Our membranes are also used for mine tailings water treatment, metal recovery, specific metal removal, and sea water reverse osmosis for process water for mining.
Acid mine drainage
X-Flow membranes are a critical part of the process of the HiPRO system. This technology produces potable water from acid mine drainage at recoveries of >98%. The gypsum waste is used to manufacture building bricks for housing developments for miners and the water produced from these plants is supplied to nearby towns as potable water. Some of the acid mine drainage references are:
- Emalalheni Water Reclamation Plant (BHP Billiton, Anglo Coal JV)
- Optimum Water Reclamation Plant (BHP Billiton)
- Kromdraai AMD Plant (Xstrata)
- Middleburg Water Reclamation Plant (BHP Energy South Africa)
Mine tailings treatment
Pentair X-Flow tubular UF membranes are currently applied in the treatment of tailings storage facilities, in order to meet new environmental standards for existing mines and mine closure. The tubular membranes are applied as a one-step treatment process.
Specific metal removal
Pentair is currently exploring the application of selenium removal with its X-Flow membranes in order to meet ultra-low discharge qualities. Conventional treatment processes are not capable of removing selenium to the ultra-low standards required.
This process is currently used in pilot trials to investigate the recovery of gold, uranium and copper from mining waste streams. Initial results have been extremely positive.
Supply of process water for mining activities
Mines located in dry and arid areas have limited access to process water. This has led to a recent boom in sea water reverse osmosis for supply of process water for mining activities. References can be found in Namibia and Chile. Ultra-filtration is the chosen technology as pre-treatment to RO. It has proven lower capital expenditure and operational expenditure costs than other technologies. Larger SWRO plants apply in-line UF-RO application which further reduces capital expenditure.