Desalination : a solution to water scarcity ?

Although most of our planet is covered in water, only three percent of it is freshwater, and only a third is available to man, the rest being frozen in glaciers or inaccessible deep underground. The ocean accounts for 95% of available water. But this is salt water. Desalinating this water could therefore be the solution to the problem of water scarcity…

Water resources are threatened by unpredictable weather conditions. Heat waves are more frequent as temperatures rise. Population growth is increasing the need for water, while resources are dwindling.

Desalination plant : a game changer

If the Earth is called the blue planet, it’s because of the ocean. The ocean accounts for 95% of available water. But this is salt water. Desalinating this water could therefore be the solution to the problem of water scarcity…

To achieve this, desalination plants are set up. Several techniques can be used.

The first is thermal distillation. This produces steam by boiling seawater. This operation leaves salt and minerals behind, but the steam is collected. It is then condensed by a cooling procedure to produce pure water.

For years, this was the main method, but a cheaper and easier-to-implement solution has now emerged.

This is membrane filtration, also known as reserve osmosis. Seawater is sprayed at high pressure through a membrane. This separates the water from its various minerals and salts.

Although this technique is less difficult, it requires a great deal of energy, and not just renewable energies.

Only wealthy countries where water is scarce use this technique.

Australia was the first country to adopt this process. The Millennium Drought, between 1997 and 2009, had serious consequences, and desalination plants were a great help.

Spain now ranks fourth in the world for desalination capacity, accounting for around 5% of the global total, behind Saudi Arabia, the United States and the United Arab Emirates.

However, many plants in the Middle East use older, fossil-fuel-powered thermal plants. As a result, desalination plants are currently responsible for the emission of 76 million tonnes of CO2 per year. As demand for desalination is set to grow, global desalination-related emissions could reach 400 million tonnes of CO2 per year by 2050.

The issues raise

Saltwater extraction in desalination plants can harm fish and other marine life if not carried out with care.

Brine is the hyper-concentrated salty liquid that is removed from freshwater. For every 100 grams of brine, there are 70 grams of salt.

This can be harmful to fish and marine life if not treated with care. If it’s simply pumped directly into the sea, this dense substance sinks to the bottom of the ocean and suffocates marine life.

Brine is denser, sinking to the seabed and creating a stratification that asphyxiates bottom-dwelling species.

Brine can contain toxic metals such as mercury, cobalt, copper, iron, zinc and nickel, as well as pesticides and acids that cause irrevocable changes to the environment.

There are techniques for distributing it over a larger area in the sea, thus diluting its impact.

Brine can contain toxic metals such as mercury, cobalt, copper, iron, zinc and and nickel, as well as pesticides and acids that cause irrevocable changes to the environment.