According to the World Economic Forum, a shortage of clean, fresh water presents the greatest global, societal, and economic risk over the next decade. Mining has always been heavily dependent on water and now there is an ever-increasing demand for mining companies to contribute towards water security, both in their operations and the communities where they operate.

Commendably, some companies are already stepping up to help protect this precious resource. GERARD PETER and LAURA CORNISH report.

THIS ARTICLE FIRST APPEARED IN MINING REVIEW AFRICA ISSUE 3, 2021
READ THE FULL DIGIMAG HERE OR SUBSCRIBE TO RECEIVE A PRINT COPY HERE

Water security is a growing concern particularly in the light of an ever-growing global population. In fact, by 2030, the global population is expected to reach 8.5 billion and could face a water shortfall of 40%. What’s more, water scarcity is a problem faced in many parts of Africa, a continent with a long history of droughts. Even more concerning is the fact that nearly 1 billion people on the continent don’t have access to clean water. Without doubt, mining has a considerable impact on water security as mines rely heavily on this important resources in their operations.

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Sadly though, mining also has a legacy of misusing water resources, including contaminating, polluting and completely decimating vital water sources. Fortunately, in recent times, there has been a greater commitment on the part of mining companies to use water resources in a more sustainable and responsible manner. In addition, responsible water usage is an important part of a company’s ESG practices, something that investors are now looking at closely. Already, some companies are taking the lead by looking at new ways to use water more efficiently and responsibly and these are those companies.

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WORKING TOWARDS A WATERLESS MINE

With 75% of Anglo American’s assets located in water-constrained areas, the company is embracing its role as a water steward to ensure a sustainable supply to its operations and the communities around them.

“The company’s Sustainable Mining Plan targets a 50% reduction in freshwater usage by 2030, against the 2015 baseline. Ultimately, however, Anglo American wants to achieve waterless mining, with its operations requiring no freshwater withdrawals,” says Jana Marais, spokesperson for Anglo American.

Among the initiatives that the company has put in place to realise waterless mining is dry tailings disposal. Water sent to tailings disposal often represents the largest water loss at a mine. Fine particle slurries in particular are difficult to dewater, and current dry disposal options have prohibitive capital and operating costs. “As part of it pioneering Concentrate the Mine concept, Anglo American is exploring low-cost methods to minimise the amount of water sent to the tailings pond in the first place,” adds Marais.

The approach combines coarse particle flotation to concentrate the mineral, and dry stacking technologies to dewater the residual waste, producing dry, stackable tailings. Essentially, it allows a mine to float particles at sizes two to three times larger than normal, making it easier to extract water from the process and leaving a waste stream that is dry and stackable.

Anglo American has been testing coarse particle flotation technology at its El Soldado operation in Chile. With the process changed to treat larger-diameter material and coarser grinding, there has been an increase in mill throughput, water, energy and cost savings, and a waste stream that is easier to handle.

However, there will always be a portion of ultra-fine particles that also require processing. In partnership with major chemical companies, the company has done some promising lab work on copper tailings using additives that separate interstitial water from fine metal particles – not only making them easier to recover but also resulting in dry, stackable tailings.

Another initiative is dry separation. “This involves finding innovative methods for dry comminution. More targeted comminution creates a pre-concentrate of the ore, rejecting and dewatering waste far earlier in the process. Early estimates indicate the potential for a 30 to 40% reduction in water used per unit of mineral production, as well as other benefits, including increased production,” adds Marais.

Marais adds that Anglo American is also exploring ways of using less water when separating waste rock from ore. Currently, the company is conducting laboratory testing of a non-aqueous processing technique by using a bespoke polymer instead of water to separate the valuable ore from the remaining waste rock particles. “Applicable across most of its core assets, the company is confident that these dry processing techniques will allow us to re-use 80% of process water, thereby moving it closer to its goal of a waterless mine,” she states.

In addition to implementing water-saving technologies, Marais explains that various initiatives are underway to increase water security in the areas where it operates by reducing its reliance on fresh water and supplying potable water to under-served host communities.

“For example, Anglo American Platinum has reduced its potable water usage, as a percentage of total water usage, from 38% in 2016 to 29% last year. This was achieved in three main ways, namely re-using water on-site; embarking on projects to use less water; and using poor quality water such as treated effluent that was not used by communities,” she explains.

To reduce its freshwater needs, the company has invested heavily in municipal wastewater treatment initiatives. These projects include upgrading the Polokwane wastewater treatment plant at a cost of around R118 million, and an ongoing effluent treatment project in Rustenburg, which will reduce its dependency on potable water from Rand Water while improving water security for the town. An added benefit is that the company pays the Polokwane, Mokopane and Rustenburg municipalities for their treated effluent, providing them with a much-needed income stream.

BUILDING A LASTING LEGACY

Precious metals miner Sibanye-Stillwater – one of the largest employers in South Africa, is likely also one of the country’s largest water consumers and water dischargers. This requires the company to examine its water management activities with strict discipline.

“Our water use management efforts demonstrate our commitment to protecting this resource and minimising our impact on consumption and discharge into the environment,” starts Grant Stuart, senior vice president: environment at Sibanye-Stillwater.

He highlights the group’s strategic objectives in this regard, as detailed in its 2020 integrated annual report:

  • Demonstrate thought leadership in water conservation and water demand management (WCWDM) practices;
  • Ensure the availability of water to support safe and productive operations
  • Minimise the impact of all operations on water resources;
  • Drive sustainable mine closure strategies; and
  • Meaningfully engage stakeholders to promote responsible water conservation and water demand management (WCWDM).

Water risk management: PGMs

Sibanye-Stillwater’s gold and PGM operations have unique and diverse water-related opportunities, challenges and risks. The group’s South African gold operations and US PGM operations (located in Montana in the United States) are water rich and so water discharge compliance and water independence from potable water sources are focus areas. The SA PGM operations are water scarce, therefore water security, for safe production, plays a key part of the WCWDM strategy.

“Water scarcity is a focus at our SA PGM operations where the Rustenburg, Kroondal and Marikana mines are located,” Stuart notes. Access to potable water is limited and added strain is emerging as a result of expanding communities.

Prolonged droughts and water scarcity has been identified as a key climate change-related water risk. Added to this is the risk of water restrictions and water cost increases imposed by municipalities as water becomes more scarce.

Mitigation measures include, among others, to implement actions to reduce water reliance from external suppliers and the development and responsible execution of WCWDM plans, based on predictive modelling.

Sibanye-Stillwater’s PGM operations used 76% of the total 23 051 Mℓ used in 2020 for industrial purposes and the remaining 24% for domestic purposes. Rand Water Board (RWB), the supplier of potable water to the PGM operations, is under severe pressure due to constrained supply to the Rustenburg region and the increasing pressure on the Integrated Vaal River System, the primary source of RWB’s water. As a result, restrictions of 20% were imposed on all consumers, including the PGM operations during much of the year under review.

“To improve our water supply security and reduce our water use, we have pursued a number of initiatives,” Stuart notes.

This includes the installation of boreholes to support Kroondal under emergency conditions. Securing alternative groundwater sources (outside of RWB supply) is also well underway with 10 Mℓ/day already secured from the Haartebeespoort canal. Optimising water recovery from tailings storage facilities through scavenger wells are further under investigation to ensure security of supply at the Marikana operation. The integration of Marikana with the Kroondal-Rustenburg footprint has further presented opportunities to balance water requirements across the footprint more specifically with the infrastructure installation to transfer excess available water from Marikana to the Kroondal and Rustenburg operations reducing our reliance on RWB.

“We are further looking at the potential to convert old open cast  pits into water storage reservoir systems which we can use for our own operational needs but importantly will also leave a positive legacy of providing additional water resources to our communities post mining,” Stuart highlights.

Importantly, the company has identified that leakages within its own circuits is a threat when dealing with water scarcity. Consequently, it has implemented an automated monitoring system across its operations (also gold) from 2016. “This has enable us to implement focused remedial measures with accuracy,” he continues.

Water risk management: Gold

By comparison with its SA PGM operations, Sibanye-Stillwater’s gold operations deal with a very different water challenge – excess water as a result of penetrating deep-level aquifers at depth. Water-related risks at these operations include regional closure, the management of the surplus water that requires continual pumping to keep underground workings dry and the treatment required to ensure the water quality is compliant when discharged.

While these deep level operations are generating significant water, Sibanye-Stillwater is currently reliant on potable water sources for some 30% of its water use. “This therefore presents us with an opportunity to find ways of becoming independent of our external water suppliers and furthermore potentially alleviate the supply challenges experienced at SA PGM operations. In 2020 the SA gold and PGM operations successfully reduced consumption by 12% year on year with our US operations largely already independent,” Stuart reveals.

Significant progress has been made in respect of driving water independence at the gold operations already. A borehole to supply the Cooke gold processing plant was completed in the first quarter of 2020, rendering the gold plant totally independent from RWB. An extension to Driefontein’s water treatment facility is also underway. The 5 Mℓ treatment extension will see the mine almost completely independent from municipal water supply by Q4, 2021. The Kloof water treatment plant, which forms part of Phase 1 of the operation’s independence drive, will reduce the reliance of the Kloof operations on RWB by approximately 33% in Q3, 2021.

Beyond this there is a major water project under review – the potential to collaborate with RWB as it looks to secure about 500 Mℓ per day of water outside of the Lesotho Highlands water scheme. “We have 200 Mℓ of water available on the West Rand, some 40% of the RWB requirement that could reduce this RWB requirement significantly – and augment the water requirements of Gauteng, the economic hub of South Africa,” Stuart shares.

Impressively, while Sibanye-Stillwater’s water management activities reside with operational improvements and cost reductions, there is significant focus in working towards improved water conditions not only for the communities around which it operates but also the greater South African economy.

COLLABORATION KEY TO WATER SECURITY

In a water stressed country such as South Africa, there is a need for this precious resource to be sustainably managed by all users. It is with this in mind that Canyon Coal has put in place a host of measures to reduce water requirements across all its mining operations, and manage this important resource responsibly at all times.

For starters, the company has a team of environmental specialists which form an integral part of the projects team, responsible for developing mines and compliance on its current operations. All of its operations are fully licensed, each with an approved Environmental Management Programme and Water Use License, which are audited internally and externally annually.

Melissa Pillay, licensing and compliance manager for Canyon Coal, explains that monitoring on all sites is conducted by independent specialists and samples are analysed in South African National Standards (SANS) accredited laboratories. “Furthermore, all of the company’s operational mines have approved Water Use Licences (WUL), issued by the Department of Water and Sanitation (DWS) in terms of the National Water Act. These WULs have very stringent conditions and employees and contractors are contractually and legally bound to adhere to these conditions,” she adds.

Flow meters are installed at all locations where water is extracted or moved between facilities at operations. The volumes are recorded to, firstly, measure compliance with the WUL conditions and, secondly, monitor the company in terms of its water use.

Pillay adds that Canyon Coal’s processing plants are equipped with filter presses which mechanically dewater the ultra-fine coal material using special filter mediums to exert pressure on the coal material to separate solids (filter cake) and liquids (clean water). “These presses result in the recycling of 30% to 40% of water, resulting in a considerable reduction in the total water use in the individual processing plants,” she states.

Moreover, the company’s mines utilise closed water reticulation systems, which ensure that no contaminated water is released from the site into the surrounding environment. All contaminated water is channelled via dirty water channels and collected in pollution control dams (PCD). This water is in turn used for dust suppression within the mine’s boundary and also pumped from the PCD back to the processing plants for reuse.”

Inflow from ground and rainwater into the opencast pits is also used to supplement the water requirements at the company’s operations, be it for dust suppression or processing requirements. The inflow water is pumped to the PCDs. This reduces the need to source water from outside the mine boundary and thus aids in preserving surrounding water resources.

In addition, Pillay points out that a Sewage Treatment Plant (STP) was recently commissioned at the company’s Khanye Colliery near Bronkhorstspruit.

The STP treats sewage water from the mine and discharges treated water into an adjacent wetland system, as stipulated in the approved the WUL.  The water quality is tested on an ongoing basis. “This contributes to the overall health of the wetland system by improving the water quality and maintaining a constant flow of water,” she concludes.