A question of balance: How miners can achieve more sustainable water use

Pretium Water Advisor IIoT water management system offers the integration of online data needed for dynamic calculations. Credit: Metso Outotec

Today, the mining industry faces sociopolitical issues due to freshwater usage and the amount of pollution created. Simultaneously, the industry is facing operational challenges caused by water scarcity and quality around the world. To keep up with increasing metal demand and decreasing mineral content in the ore, the site capacities have been growing. In general, the lower the ore grade, the more water-intensive the extraction processes is. Higher metal demand has led to 5%-plus increases in water usage anually in the mining industry. In the future, over 50% of new mining investments will be located in high to extreme water-scarce areas.

At the same time, water positive countries need to reduce the amount of effluent generated. In both cases, the closure of process water loops seems to be the only answer to improve sociopolitical issues and secure the water needed for process operation. The sociopolitical stresses have created intense pressure to use water more efficiently in the mining industry. Furthermore, laws and environmental permits that restrict the use of water are tightening. Achieving a social licence to operate is more and more critical for mining companies.

A multitude of challenges

As the mining industry uses massive amounts of water for minerals processing, water scarcity and management of vast water volumes constitute risks for the companies. The mining industry’s water cycle interconnects with the general hydrologic water cycle. In minerals and metals processing water is used from seas, rivers, lakes and even groundwater.

The level of water consumed is case and process-specific and varies greatly depending on factors such as climate, water quality, geology, ore mineralogy, mine management and practices. Due to this connection, rain, surface runoff, evaporation, infiltration and seepage all have a significant, unpredictable and often seasonal impact on the site’s water volumes and qualities. For example, tailings areas and water ponds are of particular interest as they are a tremendous and changing resource of contaminated water and interact significantly with the environment.

Mining operations also drastically change sites’ topographical and hydrological conditions. Mineralogy and water chemistry differ by location and by time. Consequently, the entire site’s water balance management should be considered as a continuous process that deserves to be followed and updated throughout the whole mine life cycle.

Water is an essential resource for the mining industry.

Minerals and metals processing requires approximately 4 cubic metres of water per ton of ore. In theory, it is possible to decrease freshwater intake to 0.2 cubic metres of water per ton of ore. However, this means that the remaining 3.8 cubic metres of water required must come from recycled process water. Solutions where process effluents are reconnected directly to the freshwater inlet of the process can jeopardize the production capacity and product quality if done without a proper understanding of the amount and quality of water to be recirculated.

New-generation water management solutions are needed

To improve water efficiency and to reduce the impacts around the mine sites, Metso Outotec develops technologies that enable a higher degree of water recycling. We believe that this is the only solution for sustainable water usage in the future.

New water management and tailings solutions decrease the overall usage of raw water and enable the use of different sources with various qualities. We aim to develop solutions that will allow closed water loops, where the required freshwater is only used to replace the water that evaporates to the sky, or fixed to the tailings sand as moisture, or removed with the final products.

New water management solutions recycle the process water before it enters the tailings ponds, increasing water recovery and hence decrease the need for freshwater intake. However, shortening of the water recycling process has some side effects in the quality of water.

A solution is emerging

Metso Outotec’s Pretium Water Advisor is a new IIoT-based water management system that helps the mining industry monitor the entire mine site’s water balance in real time. Metso Outotec’s HSC simulation software ticks in the heart of the application, a design software used for mineral industry processes design since the 1970s. It covers multi-criteria value assessment requested by the industry. This assessment includes customer value, sustainability assessment and risk assessment. It is a real end-to-end application platform that connects monitoring stations, device management, data collection, data modelling, simulation and visualization and integrates them with cloud services. This application platform enables software-as-a-service and remote service type of business and enables the fastest way to provide water management expertise for remote mining locations (see Figure 1).

The project has extended the current water balance modelling practices by integrating the dynamic production operations with the hydrological water cycle external to concentrator plants.

It opens up a web portal based data management and reporting capabilities for different stakeholders to acquire up-to-date reports that can be used for enviromental, process or investment purposes.

The system also provides the industry with the possibility to create short-term forecasts for the site’s water volumes and water quality in different production and environmental conditions. Integration of online data with the dynamic modelling tools gives real-time visibility to the entire site’s water balance. Efficient history and status reporting and predictive scenario calculations based on dynamic models enhance operational decision-making. This enables better planning of investments and use of water resources in mining operations.

In conclusion, Pretium Water Advisor was developed as a response to the common water management challenges in the mining industry, including the need to increase water recycling, fulfill environmental regulations and decrease effluent generation, minimize production losses and avoid product quality problems due to poor and fluctuating water qualities. It enables project operators to use mine sites’ water resources optimally, as a valuable raw material.

Consequently, Metso Outotec can support the mining industry by responding to investors, authorities and sociopolitical pressures that force the industry to ensure sustainable, and acceptable mining operations.

Kaj Jansson is head of Industrial Water Solutions, Metso Outotec, and Sakari Hiidenheimo is product manager, Industrial Water Plants.