By Dennis Gibson, Sergio González, Raymond Philippe and Corné Pretorius
A growing global population, rising standards of living, increased urbanization and climate change are driving an increase in water-associated risks around the world. Water is a vital component in mining operations, and the mining industry is being increasingly challenged to develop sustainable water management practices as it works to harmonize the needs of the industry, environment and society.
Recognizing the high stakes, the mining community has made huge strides when it comes to addressing water management, water efficiency and environmental impact mitigation. Improved operational efficiency and resilience planning have resulted in better risk management and more sustainable practices as the industry works to mitigate potential water conflicts between mine owners and operators, society and the environment.
The future demands more than simply meeting current standards for responsible water management. Looking ahead, miners must continually seek to deliver improved longer-term sustainable water stewardship to meet the ever increasing demand from all stakeholders, including integrated resource and proactive water management planning.
Sustainability Drives Mine Design
There is no single, one-size-fits-all approach to sustainable water use that can be applied across all mine sites. Mines are located around the world, in a variety of geographies and climates, and as such, they must work within their limitations and deal with unique challenges. Miners may face water management challenges that range from shortage to excess, and with climate change driving more erratic weather patterns, achieving sustainable water use becomes even more complex.
In the past, mines based their water use requirements on mine the plan tonnage, mineral processing treatment capacity, tailings management strategy and contingency needs. Demand needed to consider geography and climate, available water supply, processing techniques and the type of mineral being mined.
As an example, a copper mine that produces 150,000 tons of ore a day could require up to 80,000 cubic meters of make-up water per day (m3/day) to meet process and other mine water requirements. Managing several hundred thousand m3/day of fresh make up water reinforces the need for miners to prioritize regional water inventory, cumulative impacts and extend the focus beyond the mine’s boundaries and into the future considering the mine’s long-term operations and water demands.
Developing a Comprehensive Mine Water Management Plan
Mines are made up of multiple unit operations that are often designed by independent project teams and service providers, which may put miners at a disadvantage by reducing opportunities to approach water supply, treatment, recirculation and disposal processes in an integrated and holistic manner.
To avoid this issue, miners should take care to design an accurately calibrated water balance model that considers specific process-related water components, including inputs, consumption and outputs. This type of model will help determine long-term water requirements – for both quantity and quality – while helping with the design and planning the mine water infrastructure.
No matter where the mining operation is located – at the surface, underground, or open pit or strip mining – many mine functions require a specific water quality and quantity within a defined range. Defining these requirements during the earliest stages of design will allow for water management infrastructure such as storage, treatment and conveyance systems to be efficiently designed. Planners need to analyze all sources and demands on the mine’s water supply to ensure that the appropriate water quality is used, allowing for “fit for purpose” water use.
The dynamics of the mineral-processing system also play a role. It is not uncommon for the mineral processing plant to be designed independently, by a different team, and built into the water balance model as a “black box” system. The designer must be sure to take variables such as the water quality and system flows into account, which will allow the mine’s designer to better pinpoint the mine’s overall water system requirements.
The tailings storage facility (TSF) may be the largest source of impacted water at a mine, and while water quality estimates often consider the TSF water balance and effects on water quality, sometimes these variables are not integrated into the overall mine operation water balance. As new technologies allow miners to exploit lower-grade ores, generating higher volumes of waste, it will become even more critical that operators reduce the risks associated with retaining mine water in TSF. To help achieve this integration, the TSF system should be modeled as a sub-component of the larger water balance model, with its own inflows and outflows.
All other water uses at the mine must be incorporated into the overall water balance, even those not related to the operational processes. Even though these water uses may be lower in volume, they are still important, especially as they sometimes require treatment to condition the water to its final use. This includes drinking water infrastructure and water used for dust suppression, fire mitigation, vehicle wash facilities, etc.
Holistic Water Management is Crucial
Water a key component for mining and, as such, water-related risks may have significant consequences, including the loss of production and license to operate. This has elevated the crucial importance for holistic and integrated water management to the attention at the very highest levels of the organizational structure. As a result, mining companies are becoming increasingly focused on proactive, sustainable water management with many leading miners collaborating towards improving best practice through groups such as the International Council for Metals and Minerals (ICMM), representing 27 mining and metals companies towards improved sustainable mining .
To position themselves even better for the future, leading miners are seeking to building water management portfolios that combine traditional recycling and reuse with newer technologies such as advanced data analytics, treatment methods and alternative supplies. Recognizing the need to deliver more efficient services and reduce wastage, the municipal water utility industry has invested heavily in automation and remote monitoring. Mining companies that follow suit – for example, by pairing remote monitoring sensor technology with data analytics platforms – will be better positioned to meet water use targets and sustainability goals.
They are also seeking to diversify their water supply and investing in new treatment technologies (e.g., seawater or brackish desalination) to reduce freshwater requirements. The inclusion of fit-for-purpose water, allows miners to use the lowest-quality water for certain operational requirements, also helps reduce the need for treatment and impact on new freshwater demands.