How does a mine site in the desert find water?
February 09, 2023
Mining operations can work alongside communities, use fit for purpose water, explore alternative waste disposal methods, and recover and reuse water
When we think of mining, water likely isn¡¯t the first thing that comes to mind. But?most mining operations require a lot of water, and many are in arid regions in the world. Water is essential for mineral processing, tailings and waste management, and dust suppression. A medium-sized open pit mine may use and recycle eight million gallons of water every day for basic operations. So, where does it come from?
There are limited options for finding water in the desert¡ªeach with its own challenges. Mines can tap into aquifers, transport water from more plentiful regions, or import sea water. The problem with relying on aquifers is those bodies of water have competing demands with limited ability to recharge, even though they have been around for thousands of years. Some create dams or source water from more plentiful regions and transport it into the mine, though this is expensive and subject to water right claims that may be difficult to access. Pumping sea water inland for mine use likely requires extra protection against corrosion or a desalination process which adds more expense.
With limited water resources, water stewardship is becoming increasingly important in the industry. Poor water management now can create serious issues in the future, negatively impacting communities and agriculture. Let¡¯s take a look at how mining operations can work alongside communities, use fit for purpose water, explore alternative waste disposal methods, and recover and reuse water.
Many mines of the world are in deserts. They require a lot of water, so being a responsible water steward is critical.
Work alongside communities
Though it¡¯s been said before, it bears repeating. Collaborating with local communities is imperative to a sustainable mining operation. This is true when we talk about water, too. While it might be more challenging with more stakeholders, engaging with the community can be incredibly beneficial for both the mine and the community. For example, we worked with a mining client to design, build, and operate a wastewater processing facility for a municipality in Peru. The nearby city had lacked the proper infrastructure to treat wastewater and protect the natural rivers and streams. With the city in an arid desert environment, water management was tenuous to support current and future demands.? The mining company built a wastewater plant to support the city and was able to use the treated water for their mining operations instead of extracting additional water from the groundwater aquifers. It¡¯s a win-win scenario, on what we call the triple bottom line. This means the solution provided social, environmental, and financial value.
Another example is from Chile, which is home to the Atacama Desert¡ªthe driest desert in the world. Chile is rich in minerals and metals and is one of the worlds¡¯ largest exporters of copper. In Chile, most mining sites have limited water resources. So, large mining companies are building and operating desalination plants and transporting water from the ocean to use in the desert. We have supported the design of several desalination plants for large mining operations in northern Chile. In a similar vein to the Peru story, the capacity is increased by mining companies to contribute to the regional watershed demands and supplement water resources for the neighboring communities and industries not directly associated with mining.
Desalination operations are becoming more popular in coastal, arid regions of South America
Explore alternative tailings disposal methods
An increasingly necessary discussion in tailings revolves around non-traditional ways to store tailings. Alternative tailings storage and disposal methods are becoming strong drivers in the marketplace. Where they can be safely constructed, alternative methods use less water and have a smaller environmental footprint compared to conventional methods. Some popular alternative methods include thickened tailings, paste, and dry stacked tailings. These methods can reduce the volume of the stored waste and promote more stable storage while using less water. Though, there are pros and cons of alternative tailings disposal.
There is room for innovation in the tailings industry. This year, our Company entered a collaboration with Auxilium¡ªa niche technology group that reuses tailings in other industries. Auxilium specializes in alternative tailings disposal and is a tailings valorization company, meaning they provide solutions for handling waste that yield economic benefit. For example, tailings can be cleaned and made into a paste or cement. This product not only reduces water and waste, it also can sequester carbon and be reused in the construction industry for building materials.
Finding ways to responsibly manage water can benefit the mine, the environment, and the community is a winning solution.
Consider water that is ¡°fit for purpose¡±
One way to be a better water steward is to consider using water that is ¡°fit for purpose.¡± You could think of it as ¡°good enough¡± water. In mining, we can use water that has impurities. For instance, waters high in suspended solids are often present around mine sites. While the impurities are not fit for potable consumption, this water may be acceptable for mineral processing use ¡ªit doesn¡¯t need to be as clean as water that we drink. Of course, if the water is discharged, it would need to meet water quality standards to decrease environmental impact.?
Water filter systems can be effective for cleaning the water enough that it is fit for purpose.
Optimize water recovery and recycling
Another good option for saving water is to optimize water recovery where possible. Water is often lost to evaporation and runoff, so minimizing loss in these areas helps stretch the life of the water at a site. One way to do this is by using a cell system. Instead of letting water run off over a large area in the tailings facility, the area is divided into cells to minimize the surface area and therefore reduce evaporation. By reducing water loss, the mine can recover and recycle more water.
Roy Hill¡¯s Pilbara operation in Western Australia uses water from an open pit dewatering operation to recharge local aquifers. This is not only a good example of recycling water, but it also renews a local water source in an arid region. Once again, finding ways to responsibly manage water can benefit the mine, the environment, and the community is a winning solution.
Even mines in more humid locations need to be aware of their mine water balance and properly care for the natural resource and share with the surrounding communities.
What happens next?
Right now, it¡¯s up to the mining companies and individual decision-makers to optimize water use. This is not the case for other industries. For example, in the US urban planning industry, for a new municipality to form with 60,000 residents that will be supplied water by underground aquifers, there must be a ground water impact study and plan for how water will be sourced and used over the next 100 years. This ensures an adequate water supply exists before the community is developed, and that these demands don¡¯t conflict with other growing demands in the region. We need mine owners and operators to think similarly when planning for water use.
Potential impacts like regional capacity and downstream uses are considered in mining environmental impact assessments, but there is often a gap in addressing future mining growth and how it impacts the watershed. There also needs to be better integration with how community uses the shared resource. Understanding the ground water in and around a mine site is critical to ensure mining isn¡¯t damaging the environment, farming, or communities¡ªnow and into the future.
We urge mine developers and operators to fully understand their water balance and their hydrological and hydrogeological setting. What are the current demands? What are the future demands? Does a mine need to build a reservoir to retain more water and draw from that during the dry seasons? We need to recognize that it¡¯s a shared supply and, while often considered renewable, we need to recognize in arid environments, the time for an aquifer to recharge may diminish the shared capacity over time.
We need everyone to be able to benefit from the water supply, especially in arid and semi-arid climates. As stewards of our environment in the necessary extraction of metals and minerals to achieve a modern society, the future of mining depends on it.
Excerpts from this blog are included in the Engineering and Mining Journal August 2023 Issue, in the article .