The coal mining boom, in the Waterberg area of Limpopo, not only threatens the natural environment but also the scarce water resources and tourism industry of the province, mining consulting firm SRK Consulting’s Johannesburg- based principal hydrologist Peter Shepherd tells Mining Weekly.
He believes that mines in the area need to properly plan their water management strategies, while taking into account the variable rainfall and dry spells of the region to avoid polluting the area.
“South Africa needs the electricity that can be generated by the Waterberg’s coal, while the mining activities will provide much-needed jobs in the province. But we cannot afford more coal-related environmental problems, such as those experienced at the eMalahleni coalfields, where we have pollution from the coalfields entering the river systems either directly, through discharge points, or indirectly, through seepage,” says Shepherd.
Further, he says that, to sustain the many mines that are likely to be developed in the coal-rich area, water will have to be piped in, either from treated sewage or from other river basins. This is because the natural run-off in the area is unable to supply the water demands of multiple mines.
The semiarid environment of the Waterberg and the challenges of con- strained water supply are likely to make the impact of spillage on the area greater than the impact of spillage at eMalahleni. This is because there is less flowing water to dilute pollutants carried in the water, which could have devastating effects for agriculture, tourism and communities living in close proximity to the mine.
Shepherd believes that mining companies have only one chance to prevent environmental pollution in the area and, “if we get it wrong in the Waterberg, the impact will be far worse than it has been for eMalahleni, where much of the pollution has actually been diluted by its permanently flowing rivers”.
It has only been in the last decade or so that the mining industry has acknowledged the necessity of water conservation and environmental protection, says Shepherd, adding that, subsequently, mining companies have started to incorporate water-treatment facilities at mining sites.
Shepherd highlights that excess water, as a result of unusually high levels of rainfall, is another concern. Recently, at a mine in Limpopo, rainwater levels reached 400 mm in a single month. Shepherd says that “normal rainfall in the area is about 400 mm a year and, last year, nearly 250 mm fell in one day”.
Mines in the Waterberg, despite the area having a drier climate than that of eMalahleni, will need to incorporate water-treatment facilities to discharge excess groundwater entering pits, explains Shepherd. “It does not matter how good your facilities are – unusually high rainfall will result in excess water that the mine can’t store and use. Some of it has to be discharged, so a treatment facility is vital to ensure that discharged water does not contaminate the surrounding area,” he says.
He argues that water-treatment facilities need to be considered in the initial design and be factored into start-up costs. If water-treatment needs for a new project or the costs for such facilities, which should be incorporated into the financial model, are not properly understood, the results could be disastrous when it is realised the project does not have the necessary finances for the addi- tional water needed to continue with production.
Mines need a minimum of 250 ℓ for every ton of material mined, estimates Shepherd. “You might get away with less, but generally you need these levels or the mine is simply not viable and cannot be built,” he says.
Cooperation in the Waterberg
Shepherd believes that cooperation among mines operating in the Waterberg area is vital to protect the area’s environment. The Limpopo river is especially vulnerable to becoming polluted by mining operations, hence, the importance of cooperation to prevent the river from being contaminated.
“There is going to have to be some kind of corridor away from the Limpopo river, which is protected by all mining players, working together in a concerted effort. The mines may have to form some type of forum to protect the environment in this highly sensitive river basin,” he says.
The idea of a forum for dealing with water supply issues is not a new one; how- ever, the liability attached to all members makes establishing such a forum more complex.
Shepherd explains that if one member of the forum is guilty of a spill, the other members are guilty by association. “But these risks need to be worked through and should not become an excuse to dismiss the need for collaboration,” he says.
The Limpopo River basin extends into Botswana and Zimbabwe, both of which have their own mining operations, which highlights the need for cooperation at an international level. “The Limpopo river is a vital water supply for several countries and it will be impossible to protect this life-giving resource without a collective resource,” states Shepherd.
In response to whether the State should implement regulations to ensure mining operations have environment-friendly practices in place, Shepherd says: “The fact that this is a water scarce area will ensure that the mines will use environment-friendly mining practices and the State needs to ensure that water is allocated equitably to the various mines to ensure that it is not wasted.”
Fixing the Problem
Mining operations are using technological developments to improve water conservation and this needs further application, says Shepherd.
For example, it is possible to reduce evaporation from wastewater facilities by filtering slurry to extract as much water as possible for use elsewhere on site. Filter systems using a combination of gravity and mechanical pressure – sometimes producing dry tailings – are widely used at mining operations in dry climates.
“Dry tailings occur when the coal slurry is filtered and the water is sucked out of the wet slurry material. This can also be done through pressing the tailings and squashing the water from the slurry material,” he explains.
Water loss also occurs through seepage, which can be solved by lining tailings dams and increasing seepage collection facilities, he says. “Mines use liners beneath tailings dams, water reservoirs, waste-rock dumps or wherever they are required to limit the loss of water and potential contamination of groundwater resources.”
Shepherd also suggests that mines treat the water to a quality that will enable them to use it in other operational elements. This will reduce the amount of drinkable water being used in plant and mining processes by substituting it with water of a lower quality. For example, dust suppression is important to control air quality in a mine, but the process can be wasteful if the appropriate amount of water is not used. He says that if water availability was critical, the extra cost of road surfacing would have to be considered.
“If a mine only treats water at a stage where the water cannot be used elsewhere in the circuit, then they can conserve water substantially and reduce costs,” says Shepherd. “There are several technologies, such as cooling facilities, that can use dirty water more often than it is currently reused.”
However, Shepherd argues that “the mechanisms for reduced water use should be highlighted rather than the specific technologies”.
South Africa has done well in dealing with water shortages, says Shepherd, who adds that “we are not so good at preventing pollu- tion, which sterilises a lot of water, which, subsequently, reduces what is available nationally and forces us to look elsewhere to meet our growing needs”.