Drop By Drop

Mining Decisions_01 October 2017_By Toby Muir

DROP BY DROP

Effective water management in mining With water being such a scarce commodity, what new technologies are out there that focus specifically on conserving this limited resource?

It is not uncommon for the mining industry to be chastised for its water use practices, or for it to face criticism for polluting or wasting this more precious resource. In South Africa, the Water Conservation and Water Demand Management Strategy is an important means of promoting water use efficiency, and is aligned with the National Water Act, with an emphasis on effective water resource management. Despite the existing legislation, it is ultimately up to the mining houses themselves to implement effective water management programmes, and to incorporate new technologies into their operations to improve the way that water is both used and treated.

Professor Craig Sheridan, Director: Centre in Water Research and Development at the School of Chemical & Metallurgical Engineering at Wits University, believes that the mining industry is conservative and somewhat resistant to new technologies. ‘So, when a new technology does come around, the pipeline takes a while,’ he says. It is not that such technologies do not exist, as there is ‘no shortage of available technology, regardless of where you are in the world’, it is more a matter of willingness to adopt it, he adds.

Any and all new technologies being developed need to look at first and foremost at efficient water use, Prof Sheridan says. ‘So, for example, when you have a reticulation system piping from point A to point B, once it’s in your system, the focus should be around not losing it – losing it means pumping it out to a tailings facility and letting it evaporate.’ This efficiency stands true for any industry – not just mining, he says. ‘The future for any industry is around making do with what little you get without impacting society. So, going forward, it’s about cleaner production and not polluting in the first place. Though in South Africa currently, mines are generally very responsible. I think a lot of the issues we have with acid mine drainage (AMD), for example, are legacy issues – they’re an inherited responsibility,’ he says.

Laetitia Coetser, associate partner and principal water & environmental scientist at SRK Consulting, says that worldwide poor commodity prices, increased labour costs, pressure to maintain traditional mining technology rather than employing a smaller workforce, modern mining technology, and expectations from shareholders to show profits, are among the reasons why mines are reluctant to prioritise water management if capital is required. Often, the internal cost of treating water is being externalised, which have consequences for downstream users, she adds. ‘In order to achieve maximum economic returns and optimal benefits to all stakeholders, a broad range of aspects needs to be considered, including integrated water and waste management. The purpose is to reduce developmental costs, ensure environmental compliance and to reduce environmental liabilities,’ Coetser says.

AMD may be one of the best examples to illustrate not only the legacy of long-term water pollution by mines’ but also current resistance to change, Coetser says. ‘Despite progress being made in South Africa to legally address mine closure and mine water management and mining practices changing to conform to new legislation, many challenges are faced. Environmental issues, including water management, are often viewed as hurdles that need to be overcome, impacting on the profitability of a mine. Authorities are very strict up to the point of issuing licences and permits, etc., but that same level of commitment is lacking with regards to licence holders being held accountable when it comes to implementation of the management plans. The lack of enforcement of environmental legislation further contributes to the scenario.

’According to Andre van Coller, Water Geosciences Divisional Manager at Digby Wells Environmental, several new technologies and innovations have been implemented by mining companies to reduce the impact of water usage. These include treating waste streams to recover any residual value in them and also removing sulphide minerals to treat these separately in an attempt to make all the waste benign; more deposition of waste back into mine workings to reduce long-term waste impacts and fill up voids left by extraction; and separating out potential problem elements such as arsenic and antimony, and treating the smaller and more concentrated waste streams. Other efforts include better regional water management to reduce impacts and ensure that a better and more cost-effective general solution for all is found, he says, along with innovations and changes to the conventional tailings dam designs to reduce vertical seepage and improve the liner system while also reducing costs.

‘Often, new technology is not needed but the biggest improvements can be achieved by applying common sense and existing knowledge,’ Van Coller says. For example, ensuring that polluted water is fully recycled and re-used; rehabilitating open-cast mining areas to encourage surface run off and reduce ingression; and properly designing and operating waste facilities, he says. ‘These are examples of where the mining industry’s impact on quantity and quality can be greatly improved,’ he adds. ‘Management of surface water is done through storm water management and good water balances to reduce discharge to the environment by reusing/recycling as much water in the mining process as possible.

’Manda Hinsch, partner and principal water & environmental scientist at SRK Consulting, talks about some of the new technologies with which she is familiar. According to her, a pilot plant was recently built based on Barium Carbonate Disperse alkaline substrate (BDAS), which uses wood chips coated with barium to treat mine affected water. ‘Polluted water is pumped into tanks and allowed to react with the barium-coated chips, which successfully treat the mine affected water. By using this passive system, the water is being treated to almost potable standards, which provides great opportunities for use of this water by other sectors, including municipalities and irrigators,’ she explains.

Another innovative design, says Hinsch, includes the pumping of excess water from underground mining operations into a holding dam. The water is then being desalinated through a membrane plant or electro dialysis reversal (EDR), and further desalinated using spiral reverse osmoses membrane (SRO).

Meanwhile, the Water Research Commission, in partnership with Anglo Coal, Exxaro and South 32, is currently undertaking a demonstration project on 60 hectares of allocated land, which uses poor-quality mine water for soybean and wheat production.

As technology becomes more prevalent and sophisticated, so more and more data is generated. If properly analysed, this data can be useful for tailoring systems and processes to get better output. Indeed, says Coetser, big data is used to drive innovation, identify potential pitfalls and stimulate growth. ‘Modern big data platforms can assimilate vast amounts of heterogeneous, real-time inputs from multiple sources. These, in turn, extract real-time predictive and prescriptive analytics to drive operational excellence. Guesswork is replaced with information-based strategies through end-to-end simulations across the mining value chain,’ she says. ‘It is anticipated that the scale and complexity of the data generated through mining processes may create more value than any other technological innovation in the industry’s history.

’Better insight into data may result in mines being proactive rather than reactive, Coetser continues. ‘Casual data can be used at each of the mining process steps to improve operational effectiveness, enabling higher yields. Big data analytics make it possible to identify and accommodate the necessary changes without the usual risk, by providing research to support arguments for change.’ Moreover, big data may assist mines in improving production and reducing costs across a range of mining activities, she adds.

While new technologies are certainly out there, Coetser says that, traditionally, decision-makers are often reluctant to make drastic changes. ‘Historically, they tend to default to the ‘tried and tested’ rather than risk being innovative due to the potential to disrupt current operations,’ she says. ‘The challenge will therefore be to convince the mining industry to allow innovative approaches to drive decisions.’

Prof Sheridan says that when companies undertake their initial environmental impact assessments, they need to consider what will make the most sense on an ongoing basis. ‘The question is, can you derive more benefit from the resource overall than you’ll pay afterwards cleaning up what you took out?’ he asks. ‘At the moment, I’m not sure we can say that for a number of our mineral extraction processes.’ In short, it’s a matter of upfront focus, he adds. ‘Before we dig a hole, what do we want to get out of that hole and what are the forever effects? Because mining is forever. We need to put more thought into things before we do them – and that’s globally, not just in South Africa.’

Mining Decisions_Drop By Drop

Laetitia Coetser - Associate Partner | Principal Environmental Scientist

Manda Hinsch - Associate Partner | Principal Scientist

SRK Africa