Water is critical to mining operations and is used in ore processing, cooling, dust suppression, mining tailings processing, as well as dewatering to access ore and providing drinking water and sanitation facilities
Water consumption by miners results in substantial amounts of waste, including mine tailings in slurry form with a high water content.
Mining wastewater is generally highly acidic – a result of the high concentration of sulphates and metals – and has a high quantity of suspended solids. As this can potentially have a significant impact on local hydrology, miners need to consider the role of water over the entirety of a mine’s operating life.
This is especially crucial in supporting decarbonisation, where a holistic approach to managing water, from early exploration to end-of-life, can improve outcomes and minimise risk and cost. An important first step in managing water is implementing a water accounting framework.
Water accounting describes the application of a consistent and structured approach to identifying, quantifying, understanding, and communicating water interactions using a common set of metrics and approaches.
It differs from water reporting in that it is the consolidation of operational water balance information and provides the data to support water reporting for a variety of audiences and interests.
Fresh water is one of the most valuable substances recovered from tailings, especially in Australia where aridity, high evaporation, and poor-quality groundwater are common.
Maximising water recovery from tailings reduces freshwater usage and reliance on chemical and mechanical dewatering methods, while also minimising the tailings storage footprint.
Water treatment is an increasingly common way for miners to maximise the reuse of water, with various treatment technologies available such as membrane technology and thermal treatments for salt-based
pollutants, as well as bio-reactor and polymer extraction formorganic pollutant treatments.
New technologies that are being developed include dry processing, the use of seawater or desalination (though this can be costly), filtration and water reuse, and dry stacking of tailings, which is now possible at larger scales.
Treating wastewater can enable the effective recovery of water for reuse and drinking purposes, and help minimise the compliance and risks associated with overuse and discharges into the environment.
The Efficient use of water in tailings management: New technologies and environmental strategies for the future of mining paper published in the Water journal in 2022 noted the ability of a mine to operate was contingent on having sufficient water make-up to compensate for the losses incurred during operations, with most of these losses ending up in the tailings storage facility. Thus, the design of tailings storage, as well as developing an accurate water balance model, are important factors.
The researchers explained that a water management plan could provide improved water recovery from tailings for reuse in the metallurgical process, hydraulic transport of tailings or concentrate, and mine site reclamation.
Importantly, implementing a good water management plan can substantially reduce fresh water requirements and costs in the long term.
There are both economic and environmental reasons for miners to consider implementing tailings or filter cake disposal technology, as well as the supply of sea water for mining processes.
Studies have shown that these processes and technologies will be the new design and operational trends of both greenfield and brownfield mining projects. Research that looked at water recovery through a framework of circular economy in the mining industry pointed out that water recycling aimed to minimise the need for fresh or raw water, as well as reducing the volume of effluent generated and disposed of in tailings dams.
The authors explained: “By reusing and treating mine wastewater used in mining operations, the industry can conserve valuable freshwater resources by reducing the demand for freshwater, alleviating the strain on local water supplies.
“Recycling water helps to minimise the volume of liquid waste or wastewater produced during mineral processing, leading to a reduced environmental impact and ensuring compliance with governing standards.
“Overall, water recycling is vital for the mineral industry to achieve sustainable operations, conserve resources, and mitigate environmental impacts.”
They added that experimental results had demonstrated the effectiveness of advanced treatment processes – such as membrane filtration, ion exchange, and biological remediation – in removing contaminants from
mine wastewater to meet regulatory standards.
Furthermore, they noted the integration of water reuse systems with existing mineral processing operations had shown promising results in reducing freshwater consumption and minimising environmental impact.
They said: “The interpretation of these experimental findings underscores the importance of tailored approaches to water reuse that consider the specific characteristics of mining effluents and operational requirements.
“While certain treatment technologies may excel in removing specific contaminants, their practical applicability within the context of mining operations depends on factors such as scalability, reliability, and cost-effectiveness.”