The mining industry consumes large quantities of water to extract and treat minerals. However, this activity faces a growing demand for environmental and social sustainability, further accentuated by prolonged droughts that cause water scarcity. Therefore, reducing water consumption and minimizing negative impacts have become priorities for the mining industry.
Efficient water management is an essential pillar for project sustainability. Implementing advanced conservation and effluent treatment techniques is crucial to minimize environmental impact and ensure the protection of water resources.
An effective strategy is reuse, which involves different techniques for recirculating treated water to varying stages of the mining process. This can substantially reduce freshwater demand and minimize effluent generation. Currently, in Chile, water consumption is between 0.5 and 1.0 (m3/t) of processed minerals; this last data corresponds to tailings without water recirculation, the most effective being slightly below 0.45 (m3 /t) [1].
In this article, we will mention some alternatives for water reuse in the mining industry and present a case currently in operation regarding the use of tailings filters.
ALTERNATIVES FOR WATER REUSE IN THE MINING INDUSTRY
- Recovery systems: Implementing these systems in the mining process allows the process water to be treated and reused and used in one or more subsequent stages. Conventional, high-density, or paste tailings thickeners are used for this, which discharge the tailings with 55%, 67%, and 70% solids, respectively. This significantly reduces dependence on freshwater sources. In 2022, Cochilco reported a water flow of 51.34 (m³/s) [1], incorporating recirculation and reuse as an integral part of the recovery process. This recirculation percentage is planned to increase to more than 70% of the total water used in mining operations.
- Water treatment: These systems are designed to treat and purify water in mining, allowing reuse. The technologies used may include filtration, sedimentation, separation and classification using cyclones and chemical and biological treatments. These technologies can be used in parallel to maximize efficiency.
- Water recovery from filtered tailings: Tailings, or mining waste, can be filtered and dehydrated using plate filters. This process significantly reduces the water content in the tailings, obtaining a filtered solid with 18%-20% humidity and allowing the extracted water to be reused and returned to the process.
- Seawater and desalination: Seawater is an essential alternative in mining processes. It is used directly or previously treated, becoming a viable and crucial alternative for mining processes. For example, in regions with a shortage of fresh water, like in northern Chile, the desalination of seawater through the Reverse Osmosis Process emerged as an effective solution to provide water for industrial processes. This technology is especially valuable in the mining industry, where it treats saline water, industrial waste and other contaminated sources. It is estimated that by 2030, in Chile, more than 50% of the water used in mining will come from desalination processes [1], highlighting the importance and growth of this technology in the sector.
A CASE CURRENTLY IN OPERATION OF TAILINGS FILTERS
A case currently in operation involves implementing filtered tailings technology at a vital mining company in the north of the country. This technology allows the filtration and dehydration of solids, reducing the volume of water retained in the waste with less than 20% humidity. This is consistent with the previous geotechnical studies required for stability and tailings deposits. This allows the water to be recovered by reincorporating it into the same process, reaching 80% of the water recirculated.
In collaboration with Process Minerals Consulting, comprehensive advice was implemented that covered the programming, development and execution of different stages of the filtered tailings project, including water analysis campaigns. The data obtained made it possible to project the actual impact on the water balance through advanced simulations, evaluate the incorporation of new flows of treated water into the operation and calculate the ionic charge that returned to the system.
A collateral aspect analyzed through previous simulations in the replacement of conventional tailings with filtered tailings was the reduction in the flow of water eliminated, thanks to the greater recirculation implemented. This increased recirculation could eventually result in an increase in dissolved solids in the process water.
The collection of information allowed critical data to be obtained, such as the increase in ionic charge and the verification of tendencies toward scaling and corrosion in the system. With this information, optimising the plant’s water balance made it possible to project and anticipate the effects of this increase, which allows for mitigating future operational problems and improving the long-term sustainability of the process.
CONCLUSION
Evaluating the impact and feasibility of using recovered water in mining processes is essential to optimizing operational efficiency, reducing costs, and ensuring environmental sustainability.
As expert consultants, we bring technical knowledge and experience to identify the best practices and technologies. We are carrying out exhaustive evaluations that ensure a complete and balanced perspective of the positive and negative aspects, thus facilitating the optimal implementation of a project.
If you want to analyze water management in your operation, contact us at info@processminerals.cl, and we will help you. What strategy are you considering for reusing fresh water in your mining project?
Cristián Parraguez
cristian.parraguez@processminerals.cl
References.
[1] Agua en la minería del cobre, Actualización al año 2022, COCHILCO, Ministerio de Minería, Gobierno de Chile.
