Optimizing Water Recovery in Tailing Deposition Process

The path to energy transition requires high amounts of critical minerals such as lithium, cobalt, and copper, all of which involve water-intensive extraction processes. From this perspective, efficient water management become a critical challenge for the mining industries worldwide, especially in arid regions where water scarcity is a constant problem.

Regarding this context, some studies offer valuable insights into optimizing water recovery during the tailing deposition process, emphasizing the need to manage consolidation, evaporation, rehumidification, and filtration effectively.

Study Insights on Water Recovery Challenges

Wels & Robertson (2003) highlighted significant evaporation impacts, especially in inundated areas, which experience high evaporation rates due to continuous water supply and maximum downward gradients. Effective rehumidification management is crucial, as initial wetting phases can lead to substantial water losses. During initial tailings settlement, excess process water bleeds to the surface. Coarse-grained tailings settle quickly (within an hour), while fine-grained tailings take 1-2 days. About 50% of the process water is released during settlement for coarse tailings, compared to 25% for fine tailings. Following settlement, tailings consolidate due to drainage and air-drying. This stage contributes predominantly to water losses through evaporation and seepage, with little surface runoff recovery. Consolidation time varies from days for coarse-grained tailings to weeks for fine-grained tailings. As the tailings desaturate, negative pore pressures develop, leading to further consolidation. Multiple wetting-drying cycles may occur before the tailings reach a fully consolidated state.

Research by MacRobert & Blight (2013) demonstrated that natural gravitational thickening can effectively reduce water content in tailings during the discharge process, facilitating water recovery and improving structural stability. The study highlighted that within 65 hours after the cessation of deposition, the settled water content values reached those expected from mechanical paste thickening, without incurring additional costs. The results indicate that maintaining wet beaches during deposition is crucial for water release, significantly aiding in water recovery.

Finally Cavalcante & Assis (2002) showed that hydraulic segregation and staged construction affect permeability distribution, impacting short-term and long-term stability. Kalashnik (2022) further emphasized the importance of managing reconsolidation and filtration for efficient water recovery.

Mechanic Sectorization of Tailing Deposits

Conventional tailing storage facilities on relatively flat terrain require extensive land areas to accommodate the shallow angles of deposited tailings beaches. This results in a large decant pond and tailings beach area, leading to significant water losses through evaporation. Sectorizing a tailings deposit into individual segments or dikes reduces the tailings beach area, significantly lowering evaporation losses on the beaches and re-saturation areas. Successfully employed at the Chuquicamata mine in the Atacama Desert, this method has reported a reduction in fresh water consumption of up to 0.07 m3/t.

While mechanic sectorization is an effective method for optimizing water recovery in tailings deposits, it comes with several challenges, including high initial costs, complex planning and design, maintenance requirements, limited flexibility, and safety concerns.

Despite numerous studies and efforts dedicated to improving water management in tailings dam facilities, several challenges continue to hinder these initiatives. The primary difficulties stem from the risks and safety controls necessary to operate in harsh conditions and the vast geographical extent of these impoundments. These factors often render some suggested improvements impractical.

Conclusions

Optimizing water recovery in tailing deposition processes requires a comprehensive understanding and effective management of consolidation, evaporation, rehumidification, and filtration processes. Academic insights and mechanistic sectorization efforts depend heavily on precise control over discharge points and deposition areas, as they significantly impact the increase in superficial water runoff.

Some suggested practices that can be extracted include keeping tailings beaches wet during deposition to enhance water release and recovery, regularly rotating discharge points to prevent the development of large active deposition areas, and reducing seepage and evaporation losses. These management practices can provide a more flexible and cost-effective solution. However, despite the effectiveness of these practices, there is still a challenge in determining when and where to change the tailing deposition arrangement to maximize surface water runoff and overall water recovery.

To overcome these challenges, integrating advanced technologies such as remote sensing and satellite imagery, GIS modeling powered by machine learning algorithms can enable real-time monitoring and adjustments. This approach reduces the need for extensive physical modifications and can classify the perfect ground moisture point, location, and predict the beach area to optimize tailing discharge. Implementing these technological solutions offers a more flexible and cost-effective approach to maximizing overall water recovery in tailing deposition processes.