How Brine Mining Could Provide Drought-Stricken Tenerife With Clean, Healthy Drinking Water

As it battles through one of the worst droughts in living memory, the Spanish island of Tenerife is forced to rely on desalination plants to battle water shortages. As the search for sustainable solutions picks up, researchers are exploring innovative methods, such as brine mining, to extract vital minerals from seawater in a race against time to secure the island’s future and long-lasting water security for its people.

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Water scarcity is an issue that is affecting more countries and regions, especially in the southern part of Europe. After one of the driest winters in recent history, in February 2024, Tenerife declared a drought emergency.

Despite being one of the greener Canary Islands, Tenerife has suffered a critical lack of rain during the usually wetter winter months, exacerbated by the islands’ semi-arid climate, low rainfall, and high evaporation rates. In recent years, rainfall has decreased by between 15-40% and water evaporation has increased by between 10-25% in the island’s agricultural midlands due to rising temperatures.

Recovered Water Is Too Pure

To mitigate these problems, the Canary Islands heavily relies on desalination plants. At present, the archipelago has 28 large desalination plants supplying water for domestic and industrial usages. Tenerife is home to five of them: La Caleta, Adeje Arona, Santa Cruz, Granadilla and Fonsalia.

The primary technology used in these plants is reverse osmosis. This water purification method pushes seawater through a semipermeable membrane by using high pressure. Water is first filtered to remove large particles and chlorines, before being pumped under high pressure to pass through a membrane with tiny pores. These pores allow only the water molecules to pass while blocking most contaminants. The clean and purified water is then collected.

While effective, reverse osmosis produces water that is almost too pure; it lacks the minerals necessary for human health, such as calcium, magnesium oxides, hydroxides, and carbonates, making a remineralisation step a necessity. Minerals are essential for the basic functions of the human body to take place: they help, among others, to control bone growth, regulate fluids, normalize nerve and muscle functions, keep up metabolism, and grow connective tissues.

“Currently in the Canary Islands we do not have some of these components like calcite, therefore we bring calcite from the mainland,” explained Antonio Garcia from the Depuration and Desalination department in Aqualia, a Spanish company specialized in the integration of the water cycle management.

The carbon footprint of this process is quite high since this calcite is coming from traditional mining and afterwards it needs to be shipped to the island.

One alternative could be to extract essential minerals and metals important for drinkable water directly from the brine, a by-product produced from the desalination process.

“Brine mining can be a way to extract minerals and metals in a more sustainable way compared to conventional mining where you need to mine large tracts of land,” said Naiara Hernández, a researcher at Aqualia’s R&D department.

Minerals and Metals From Seawater

There are many initiatives that are trying to work on this issue. For instance, researchers from the Massachusetts Institute of Technology (MIT) are developing methods to convert desalination brine into useful chemicals such as sodium hydroxide or hydrochloric acid that are essential in the water treatment process.

Another initiative is the European research project Sea4Value, which aims to extract valuable minerals and metals from the brine produced by seawater desalination plants. The project features a pilot plant at the Water and Added Value European Entrepreneurship (WAVE) centre, a research center in desalination and brine valorisation of Aqualia. The center is located next to the Seawater Desalination Plant of La Caleta, a desalination facility in the municipality of Adeje, Tenerife, where various technologies are being tested and optimized outside the lab in real-world conditions.

The project is examining different types of brines, including those from the Atlantic Ocean. One of their objectives is to enhance water security and supply while reducing dependency on raw material imports. Desalination plants could benefit from incorporating certain recovered minerals and metals into their remineralisation processes during reverse osmosis.

The pilot plant is testing technologies like calcium precipitation and advanced membrane crystallization, which aim to recover calcium, as well as binary extractant solvent extraction, which is being evaluated for its potential to recover magnesium. These technologies could improve the efficiency of desalination plants and provide valuable resources from what was previously considered waste.

But the project is facing challenges because the technology is so new.

“We are not only focused on the recovery of majority compounds from the brine, but we also intend to recover minerals and metals that are in low concentration. This is a huge challenge because the technologies that exist today are not close to being implemented in the market,” said Hernández.

Another challenge comes from market requirements. The purity and quality of certain components require exhaustive purification and extraction techniques to make sure the compounds meet the required standards.

Future

Years with low water volumes, along with population and tourist growth and the rich agriculture on the island, mean that the demand for water is increasingly high,” said Garcia. Looking ahead, addressing water scarcity in regions like Tenerife demands innovative solutions that go beyond traditional desalination practices.

Embracing circular approaches, such as brine mining for essential minerals and metals, offers a more sustainable alternative to conventional mining and unlocks valuable resources from what was once considered waste.

Featured image: European Science Communication Institute.