BHP builds a technologically advanced desalination plant, near the Port of Coloso, to deliver water to the Escondida mine in Chile.

Investigating current and emerging trends in mining desalination projects in Chile

By Jim Spenceley

Sustainable development will continue to be a growing force within the mining industry, particularly as global pressures drive demand for the metals and minerals that the mining industry provides. Water is a critical component in mining operations, and effective water management has long been a focus for miners as they work to improve water efficiency and reduce environmental impacts.

But the world has a finite amount of freshwater, and under intensifying pressure from rising industrialization, urbanization, a growing global population and climate change, water-associated risks are expected to increase proportionally. It’s no secret that competing demands on water resources can create insecurities if not appropriately addressed and managed.

Recognizing the critical need to address the global water supply, the United Nations has declared the decade spanning 2018-2028 as an International Decade for Action in “Water for Sustainable Development,” and released accompanying sustainable development goals (SDGs) that emphasize sustainable development and integrated water resources management.

The International Council on Mining and Metals (ICMM) has established 10 principles that map against the UN’s SDGs and offer a best-practice framework for sustainable development in the mining and metals sector. ICMM member companies are committed to these 10 principles and are encouraged to transparently report their performance involving water, energy and their environmental and social stewardship.

For example, Anglo American has said it is “ultimately aiming for a future where we’ve created waterless, carbon-neutral mines,” while Rio Tinto has moved toward focusing on site-specific water use targets to meet local needs and conditions. BHP is taking strides to reduce freshwater withdrawals by 15% by fiscal year (FY) 2022 and prioritize integrated water resource management by FY 2030. South32 is taking a holistic approach centered on promoting better water use, effective catchment management and improved water security — and by doing so, has reduced its total FY 2019 water inputs by 6% and improved water efficiency by 3%.

As a significant global consumer of water, the mining industry is responsible for playing an important role when it comes to sustainably managing water resources. As the global mining industry continues to develop new mines to replace reserves and production, the challenges of dealing with lower-grade ores — which require more water to produce equivalent product as higher-grade ores — will challenge the sector to be increasingly innovative as it strives to drive toward more efficient water management, balancing its needs with those of society and the environment.

The Drive for Copper

As the world continues to march toward a more sustainable and energy-efficient future, demand for copper is expected to rise over the next decade. Global population growth, urbanization and the proliferation of electric vehicles (EVs) will increase the demand for copper. And, with sales of EVs expected to rise to 8% of the global fleet by 2035, demand for copper due to EVs alone is estimated to increase by 1.7 million metric tons (mt) by 2027.

Chile is the world’s largest copper producer, providing nearly one-third of the global supply. Copper mining is a pillar of the Chilean economy and is credited with driving economic development there over the last 30 years. According to industry estimates, over the last two decades, copper mining has accounted for an average of 10% of Chile’s gross domestic product (GDP). In comparison, the mining industry as a whole represents 11% of the country’s GDP.

Most of these mines are concentrated in northern Chile, in the Atacama Desert, one of the driest regions on Earth with an average annual rainfall of about 0.6 in. The terrain is mountainous, high in elevation, and features a complex desert ecosystem.

In this region, increasing drought and decreasing rainfall are driving concerns that Chile will be severely impacted by water shortages over the coming decades. To address this, the Chilean Congress is discussing new amendments to the Water Code that would limit freshwater withdrawals. As a result, the mining industry is facing pressure to decrease its freshwater withdrawals and to use seawater, either through direct seawater flotation or desalination to produce freshwater.

Desalination Offers Long-term Solutions

Desalination offers a sustainable long-term solution. Only 2.5% of the world’s water is freshwater. If all the water on the planet was collected into a one-gallon jug, available freshwater would comprise less than 2 tablespoons.

Even as miners deal with current water scarcity issues, the declining quality of ore is causing additional concern throughout the industry, as miners must use greater amounts of water and energy to process ever-larger amounts of ore. In fact, the Chilean Copper Commission (Cochilco) estimates that higher water intensity in ore processing will more than triple the industry’s seawater consumption by 2029. The group added, “It is important to note that Chile’s copper production matrix is expected to change over the coming years, shifting toward sulfide mineral whose treatment involves the water-intensive flotation process.”

And with nearly half (46%) of the world’s copper coming from ICMM member companies, pressure is mounting as these miners work to adhere to the 10 principles. With this and the potentially changing regulations in mind, Cochilco said that based on current trends, seawater will account for 43% of the water required by the country’s copper mining industry by 2029.

The Escondida Water Supply (EWS) project pumps desalinated freshwater more than 180 km (100 miles) to the mine, which sits more than 3,000 m above sea level.

Building Major Desalination Project in Northern Chile

Although the concept of desalination has been around for centuries, modern large-scale desalination has only been around for decades. Adapting the engineering and construction of a conventional desalination plant and pipeline conveyance system to the mining industry’s stringent safety, quality, availability and reliability requirements is essential. These systems must be designed and constructed to provide reliable water supply for the life of mine.

In northern Chile, these technologically advanced desalination plants are built along the coast, the desalinated water is moved through an accompanying conveyance system — a complex system of pipelines and pumping infrastructure — over long distances to the high elevations of the mine site. The resulting brine is released back into the sea through a sophisticated dispersion system designed to reduce brine concentrations to ambient levels efficiently and over the shortest distances possible.

Perhaps no name has aligned itself as a leader in desalination more so than BHP Billiton, which continues to lead the way with its Escondida Water Supply (EWS) project. BHP needed to develop a sustainable long-term water supply solution for its Minera Escondida copper mine, located in the Atacama Desert. The miner decided that desalination provided the best opportunity to improve operations while protecting the environment. By relying on water from the sea, BHP could reduce its freshwater withdrawals, saving those resources for the local communities and area ecosystems.

To deliver desalinated water to the mine site, BHP built and commissioned a technologically advanced desalination plant, conveyance system and associated infrastructure. The desalination plant is located at the port of Coloso, and the desalinated freshwater is pumped over more than 180 km (100 miles) in distance and upward approximately 3,000 m in elevation to the mine.

The conveyance system relies on two 42-in. buried pipelines and four pump stations to deliver up to 2.5 m3 of water per second (m3/s) to the mine. A throughput expansion to the plant is also nearly completed making it the largest desalination plant in the Western Hemisphere. Additionally, the marine intake and outfall used innovative micro-tunneling to install the infrastructure, minimizing disturbances to the delicate marine eco-system and reducing disruptions to the local fishing community.

This allows BHP to rely on desalinated water, reducing its withdrawals from aquifers and offering a more sustainable water solution. As a leader in safety and sustainability, BHP’s success with EWS blazes a new path forward for sustainable mining in northern Chile.

The system relies on two 42-in. buried pipelines and four pump stations to deliver up to 2.5 m3/s of water to the mine, making it the largest desalination plant in the Western Hemisphere.

Desalination Cost Levers

Capital efficiency is critical for investments and there are important considerations when designing a major desalination plant and conveyance system. A new copper mine can be a multibillion-dollar investment and infrastructure comprises a significant portion of that capital, particularly when it comes to building a desalination and conveyance system.

Key cost drivers can be organized into four areas: program, site conditions, community and environmental concerns, and execution strategy.

Under the program category, the class of the facility and the expected design life are major cost levers. There is a significant cost difference between a 20-year facility and a 40-year facility. Other variables include the raw seawater quality, local energy costs, treatment goals (production flowrates, RO recovery, finished water quality, etc.), as well as the technology requirements, including redundancy and availability and pilot studies for pretreatment selection and process optimization. For conveyance systems, local topography and proximity between the desalination plant site and the mine will be major cost levers, as well as the selection of corrosion protection plan for pump station and pipeline materials, which must be weighed against selected finished water quality goals.

Site conditions also present significant cost variables. Many times, sites will be remote and new roadways will need to be installed to access these areas. This is especially true for those sites along conveyance routes where topography and hydraulics drive site selection over ease of access. These remote sites also must consider the challenges associated with travel time for delivery of equipment and materials and time required for operators to commute to a site to respond to disruptions in operations. This frequently results in these sites being completely operated remotely from control stations either at the mine or at the desalination plant, both of which warrant full-time operations staff.

Community and environmental concerns will also impact cost. Working in both the marine environment as well as the terra firma landscape will present different challenges. Miners must comply with restrictions on shoreline work when building out the marine infrastructure (e.g., tunneling vs. open trench), and adhere to all environmental politics and regulations — obtaining the correct permits, mitigating the impact to any local threatened or endangered species, and being considerate of any local fishing communities, which may depend on the local marine ecosystem. Furthermore, daily changes in ocean conditions can be a notable driver on productivities for marine work during construction and regular maintenance periods as periods of high winds and waves can restrict work-at-sea.

Execution strategy, including the commercial approach, can have a major impact on cost. Engineering, Procurement and Construction Management (EPCM), Engineering, Procurement and Construction (EPC), and Build-Own-Operate-Transfer (BOOT) contracts are commonly considered. This selection can impact not only the total installed cost of the project but can also shift costs from capital expenses to operating expenses and vice versa. The project schedule will also dictate cost.

The proper composition of the project delivery team is also critical, using local team members with an understanding of local labor markets and local material supply combined with global expertise in desalination, other treatment systems, and the significant expertise required for complex conveyance systems. Finally, as much of the major desalination equipment will be supplied from global equipment suppliers, an effective sourcing strategy will also be critical.

Emerging Trends in Mine Water Today

Miners are studying and implementing multiple alternative options to help ensure long-term water security. The outcomes and adaptations of these ongoing efforts will shape the future of how copper miners source and manage water in northern Chile.

Desalination water supply will become the norm. Large-scale desal will continue to play a role in copper mining in northern Chile, especially in water-stressed areas such as the Atacama, where all greenfield copper projects — and most major existing operations — are planning for a desalinated water supply (or seawater flotation). BHP led the way with their EWS project, and with another desalination plant under construction at Spence, the trajectory has now been set. In fact, at least eight new mining projects are planned around the use of seawater, with four expansions of existing systems.

Filtered tailings for water reuse. Huge amounts of water are trapped in tailings, and some miners are investigating using large-scale tailings filter systems to recover water. These systems are being trialed at multiple mines and expect to see more trials and production-scale systems down the road.

Major water reuse and treatment projects. Miners all have initiatives to use less water, and water reuse, recovery and recycling initiatives will continue to be a major priority. This includes managing evaporation, controlling contact water, producing higher density tailings, and investing in alternative water treatment technologies beyond reverse osmosis, to name a few. But a critical component of recycling and reuse is managing the levels of contaminants that build up in the process water — as more water is recycled, more treatment is required to maintain the quality of the process water being used. 

Larger-scale water treatment and exchange programs. Miners are studying their water security options, which can include moving water between basins and water exchange programs with local communities. These programs could involve treating and reinjecting water into basins and aquifer recharging systems, providing new infrastructure for communities to facilitate sharing of water resources and reuse of municipal wastewater.

Floating solar on water reservoirs. Installing floating solar arrays on reservoirs offers two major benefits: renewable energy generation and evaporation prevention. Evaporative loss of water is significant in northern Chile, and multiple studies are currently in progress with some small-scale facilities already installed.

Integration with pumped hydro storage. An exciting new development is the integration of desalination, pumped hydro storage and renewable energy at grid scale. Combining these technologies together — each proven in their own right — is likely the best way to deliver freshwater while providing renewable energy generation and low-cost energy storage. The topography and solar resources of northern Chile are well-suited for these integrated projects by providing access to both seawater as well as to the higher elevations necessary to situate the upper reservoirs. Coupling seawater pumped hydro storage with renewable energy installations provides an excellent opportunity to lower the operation cost of desalination facilities since the head pressure of the upper reservoir can be used, and today there are multiple studies under way by private developers in multiple locations.

The future of the Chilean copper mining industry is bright, as shifting global trends and rising demand continue to support a robust market. But challenges abound — miners must use greater amounts of water and energy to process lower-grade ore, even as they work to meet increasingly stringent regulatory and sustainability targets. This is causing miners to take additional consideration when building new greenfield projects or investing in mine expansions.

Miners will continue to play a significant role when it comes to sustainably managing water resources in northern Chile. Desalination and the use of seawater will be areas of major investment going forward and will continue to offer new opportunity when it comes to achieving their water security and sustainability objectives.

As the world’s largest producer of copper and a major mining center, Chile can be a true leader in sustainable mining. By embracing innovation and collaboration, miners can drive toward more efficient water management while balancing the needs of the sector with those of society and the environment, helping to define a new future of sustainable mining.

Spenceley is senior vice president of Black & Veatch Mining, where he is responsible for developing new and existing client relationships while leading business development, financial management, engineering, operations and construction. Spenceley has 25 years of experience in mega-project execution, greenfield project development, brownfield expansions, and open-pit and underground mines. He has extensive international experience, having served as an international project director and group executive responsible for global project services for Newmont Mining Corp., and has lived and worked in Chile, Ghana, Canada, Australia, Indonesia and the U.S.