There are 1,386 million cubic kilometres of water in the world, of which 97.5% is salty and 2.5% is fresh. These numbers have remained stable for two billion years. Growing domestic and industrial consumption leads us to seek alternatives for obtaining and supplying fresh water.
Data from FAO's Global Information System on water resources and agriculture, AQUASTAT, indicate that the availability of renewable fresh water is declining at a rate of 10% per year.
Globally, about 3,269.81 billion m3 of fresh water are currently extracted for human consumption. Approximately half is not consumed (it evaporates, infiltrates the soil, or returns to a bed) and, of the other half, it is estimated that 65% is destined for agriculture, 25% for industry. Only 10% is allocated for domestic consumption. In Argentina, 37.78 billion m3 of fresh water are extracted per year, of which 73.93% is destined for agricultural use, 10.59% for industrial use and 15.48% for domestic use.
In this context, we must first analyse where the water we have for all types of consumption comes from. We can consider four sources of water, of which only two are fresh water:
Climate change and the consequent changes in weather conditions alter the availability of water from all these sources. At the same time, water becomes an increasingly demanded resource. The water problem was included in 5 of the 17 Sustainable Development Goals of the 2030 Agenda of the United Nations (UN):
Water is a key resource for production and its shortage dramatically influences economic growth. The World Bank estimates that, because of the lack of water, economic growth rates in some regions could decrease by up to 6% of GDP in 2050.
The desalination process appears in response to the loss of fresh water reservoirs suitable for extraction. Through this method, the salts dissolved in the water are removed, making it suitable for human consumption and industrial or agricultural use.
Obtaining fresh water from salt water dates back thousands of years. It is believed that Thales of Miletus, in 600 BC had already experimented with evaporation for desalination, but it was not until 1965 that the most used technique today was developed: reverse osmosis.
Semipermeable membranes are used to separates the salts from water.
This process enables the separation of salts using semipermeable membranes, through which water passes, but not the particles dissolved in it. This method involves the use of an external pressure that overcomes the osmotic pressure to reverse the flow of the solvent (water) in a natural osmosis process. RO allows the removal of salts and low molecular weight organic compounds, producing high-quality drinking water.
Removes ionic components under the driving force of an electric current from aqueous solutions through ion-exchange membranes. The membranes allow the passage of ions that are transferred to a higher concentration solution.
It works the same as reverse osmosis, but its membranes offer greater resistance to the passage of some ions and a higher rejection percentage, which allows it to operate at lower pressures.
Its basic principle is to provide heat to the water, evaporating it and then condensing it. Since the salts are not volatile, this facilitates desalination.
It consists of evaporating water in between 15 and 25 different stages, with decreasing pressures and temperatures in each of them. The water is preheated in each of the chambers, and when it goes to the next one and has a lower pressure, the water evaporates, leaving the salts at the bottom of the tank. The steam generated is condensed and converted into water with a low saline concentration.
This technique is similar to MSF. Vertical and horizontal tubes with hot steam are used and on which the inlet water is sprayed to act as a heat exchanger. Thus, the steam condenses inside the tubes, while the water outside evaporates. The salt-free steam passes to the next chamber/stage, where it will heat the inner side of the tube and evaporate the water on the outside. This process consists of between 5 and 20 stages and only requires applying external heat to the first one.
In recent years, the Latin American and Caribbean region has become one of the main emerging desalination markets. The Inter-American Development Bank (IADB) indicates that there are 30 desalination plants on the continent. Furthermore, industry projections estimate that in the short term more than US$20 billion will be invested in technologies and new projects.
It is estimated, in turn, that globally the market will grow at a compound annual growth rate of 8.77% between 2022 and 2027. In Argentina, constant growth is expected in the coming years. In fact, in the Province of Buenos Aires there are 10 plants, in Santa Cruz there are 3 and there are projects to inaugurate new desalination stations, especially near the Paraná River. The Government of Santa Cruz estimates that by 2050, 40% of drinking water will be desalinated.
Although reports from the Argentine Chamber of Mining Entrepreneurs (CAEM) indicate that the mining activity uses less than 1% of total water consumption, it is an essential resource in the different stages of the extraction processes. In fact, data published in advance of the 6th Annual International Conference and Exhibition ‘Desalination Latin America’ organized by Vostock Capital, states that seawater will increase its importance as a global supply for the mining sector. Today its use is 9% and in 2025 it is estimated that sea water will represent 36% of the water used in this sector.
Estanislao de León, Audit Partner and spokesperson for the Energy and Natural Resources industry at Grant Thornton Argentina, highlights the importance of Green Energy for desalination. "It is an industry that is expanding throughout the region. The transition from fossil fuels to clean energy will allow us to reduce the carbon footprint, while satisfying the demand for water without depleting the resource".
In mining activities, water is used for cooling, cleaning and lubricating drilling and cutting tools, to avoid excess dust, to transport minerals, waste management and to restore land and revegetation. It is also essential for hydrometallurgical processes, widely used in the extraction, separation, and recovery of metals such as gold, copper and zinc through liquid solutions.
"Although it does not represent a high consumption compared to other industries, mining areas tend to be arid and have difficult access to fresh water. Desalination would allow the exploitations to have the necessary supply without affecting the water for the communities that live close to the exploitation area", says de León.
The Chilean Copper Commission (COCHILCO) indicates that in 2021 the extraction of water for the production of 5,625 tons of copper was 17.58 m3/sec, of which 12.87 m3/sec were used for the concentration of minerals, their processing and classification. An increase is projected for the 2024-2033 period.
This is why the reduction in the use of continental water and the promotion of different sources that do not compromise the supply for human consumption must be on the agenda of Governments and companies. The circular economy in water management for the use of recycled and treated water must also be reinforced.
The implementation of a triple helix model, where Government, Industry and Community ensure and work towards responsible and sustainable consumption of water, can be the beginning of the development of policies and regulations, not only on fresh water, but also on desalination. Collaboration with local communities is an essential factor, since they could also benefit from desalination and could exercise an external control mechanism in the proper use of resources by companies.
"The mining industry in Argentina has sustainable growth as its ultimate goal, which makes the feasible incorporation of the desalination process relevant, since it would help reduce the use of drinking water in the production process" concludes Estanislao de León.
i. blogs.iadb.org - Desalinización: ¿el futuro del agua?
ii. desalinationlatinamerica.com - Datos y cifras de la industria.
iii. noticias.santacruz.gob.ar - Plantas de Ósmosis: El futuro es la desalinización del agua de mar.
iv. www.bancomundial.org - Agua: Panorama general.
v. www.caem.com.ar - Minería argentina, todas las respuestas. Agua y minería.
vi. www.cochilco.cl - Water consumption and projected demand in Chile's copper mining