How Desalination Works (and 5 Reasons It’s Vital for Our Future)

Global water scarcity is something of a paradox. Water covers almost two-thirds of the planet’s surface, yet freshwater—the stuff we use for drinking, showering, and other vital purposes—is tremendously scarce.

A mere 3 percent of the earth’s water is fresh, but most of it is locked up in glaciers and ice caps or otherwise inaccessible. The remaining 97 percent is seawater, which is unfit for human consumption. But what if we could turn that salty ocean water into drinkable water? As strange as this might sound, it’s precisely what many governments and companies are pursuing with desalination.

In this article, we’ll take a deep dive into the booming desalination industry. But first, let’s look at what desalination is, how it works, and most importantly, its role in addressing the global water crisis.

What is Desalination?

The U.S. Department of Energy defines desalination (de-sal, for short) as “the process of removing salts and other minerals from water to make it suitable for human consumption, irrigation, or industrial uses.” Essentially, desalination involves converting the vast saltwater reserves in the world’s oceans and seas into usable freshwater. It also cleans brackish (salty) groundwater, agricultural runoff, industrial effluent, treated wastewater, and other liquid waste.

With solar, nuclear, and other renewable energy sources making energy more affordable and abundant, seawater desalination is fast becoming an ever more crucial freshwater source worldwide, especially in arid regions with prolonged droughts or limited freshwater resources.

How Desalination Works

There are numerous ways to separate salt from water, but they often boil down to two distinct methods: thermal desalination and membrane-based desalination.

Thermal Desalination

Thermal desalination is the older of the two processes, producing about 25 percent of desalinated water globally. Thermally-driven systems heat seawater into steam, leaving the salty brine behind. The steam then condenses back into freshwater when cooled.

The most common thermal method is Multi-Stage Flash Distillation (MFD), where seawater is heated and then quickly moved into a low-pressure chamber, causing it to vaporize or “flash” into steam instantly. This occurs in several stages, each at a lower pressure than the last, to maximize efficiency.

Multiple-Effect Distillation (MED), another thermal method, uses a series of chambers, each with lower pressure and temperature than the previous one. The steam from one chamber is used to heat the water in the next, making the process more energy-efficient, especially when combined with heat from power plants.

Membrane-Based Desalination

Unlike thermal desalination, which relies on evaporation and condensation processes, membrane-based desalination uses special microscopic membranes to recycle salt water. The most widely used de-sal membrane-based technology is reverse osmosis (RO). According to a U.S. Bureau of Reclamation report, over 70 percent of desalination plants nationwide use this process.

In RO, high-pressure pumps force seawater through a semi-permeable membrane, leaving highly concentrated salt brine on one side of the membrane and allowing water molecules to pass through to the other side. Usually, the water is pre-treated before reaching this delicate membrane to avoid clogging or fouling it and impairing its performance. To achieve this, sediment filters are positioned to physically remove larger particles like rocks, dirt, sand, microplastics, biological waste, and other unwanted elements in the water. What’s left is pre-treated water with the salts and minerals ready to be removed.

Reverse osmosis has become the dominant desalination technology worldwide because it’s more energy-efficient than thermal methods. However, a significant amount of energy is still required to create the high pressure needed to push water through the membranes.

Learn more: Reverse Osmosis Water Filtration Explained

Desalination is Vital for Our Future

• It could help solve the world’s drinking water shortage.

We all know clean water is incredibly crucial to our well-being and survival. We need it for drinking, cooking, hygiene, and household purposes. On a larger scale, hospitals, schools, businesses, farms, and industries need a steady supply of potable water to remain in operation.

While rivers, lakes, and underground reservoirs provide much of this freshwater, rapid population growth, urbanization, agriculture, and industries, among other things, are rapidly depleting these already-limited freshwater reserves. As of 2022, some 2.2 billion people lacked access to safely managed drinking water. Worse, there’s a projected 40% global shortfall in freshwater resources by 2030 and a 20 to 50 percent increase in demand by 2050.

By tapping into the ocean’s abundant saltwater supply, desalination could produce virtually limitless amounts of fresh water to reduce the impact of droughts and avert global water scarcity—one of the top 10 threats facing the world in the next decade, according to the World Economic Forum’s Global Risks Report 2024.

• It could increase global food security.

Besides providing adequate drinking water, desalination can also supply adequate freshwater for agricultural irrigation, which is the largest consumer of freshwater globally. U.S. farms consume over 83 million acre-feet (more than 27 trillion gallons) of irrigation water every year — the second most water-intensive industry in the country, after thermoelectric power.

The Global Adoption of Desalination

Today, over 20,000 desalination plants operate worldwide, producing about 95 million cubic meters of freshwater daily for 300 million people in 150 countries. With very little freshwater and large reserves of fossil fuels to power de-sal plants, Saudi Arabia produces the most freshwater of any nation. Neighboring countries like the United Arab Emirates (UAE), Kuwait, Qatar, Oman, and Bahrain also rely heavily on desalination for their freshwater supply.

Outside the Middle East, major players like Australia, Libya, Algeria, and Israel are making significant investments in desalination to offset the challenges of water scarcity from prolonged droughts and other factors. Even industrialized nations like the United States embrace desalination, especially in water-strapped states like California and parts of Florida.

With booming populations and worsening climate conditions shrinking freshwater reserves, desalination is quickly coming into play in many other places worldwide. Plus, as the technology becomes more efficient and cost-effective, it’s likely to be adopted in more developing countries.

Breakthrough Innovations in Desalination Technology

As technology evolves, we’re seeing more breakthroughs in desalination that could reshape the future of water. For instance, engineers from the Massachusetts Institute of Technology (MIT) and China have developed a new solar desalination system that supposedly could produce freshwater that is cheaper than tap water.

This solar-powered device works by taking in saltwater and heating it with natural sunlight—a setup that allows water to circulate in swirling eddies. This motion, alongside the sun’s heat, causes the water to evaporate, leaving salt behind. The resulting water vapor is then condensed and collected as pure, drinkable water. The researchers envision that a scaled-up version of this device could passively produce enough drinking water to meet the daily requirements of a small family. It could be particularly beneficial for off-grid coastal communities with easy access to seawater.

Furthermore, a host of technologies are being developed, not just to turn seawater into drinking water, but also to reuse everything from agricultural water to industrial effluent.

4 Potential Uses of Saline Solutions at Home

While on the topic of desalination, we should note that although brackish water isn’t ideal for drinking and various other purposes, saline water (a mixture of water and 0.9 percent salt) can be a powerful remedy for a host of health conditions. Whether you buy it at the store or make your saline solution at home, there are many ways you can benefit from it:

Clearing Sinuses

If you or a loved one is experiencing stuffiness or nasal congestion due to a cold, allergy, or sinusitis, saline solutions can provide much-needed relief, Medical News Today explains. When used with a neti pot or nasal spray, the salt gently flushes out excess mucus and bacteria and moisturizes nasal passages for better breathing.

Soothing a Sore Throat

If you’ve ever had a sore throat, you were probably told to gargle with salt water—and rightfully so. Healthline notes saltwater gargles are “especially effective for colds or flus that cause a mild sore throat.” It supposedly helps soothe the lining of the throat to provide temporary relief from pain and has mild antibacterial properties that can help combat minor throat infections. Many people find this remedy especially beneficial during the cold and flu seasons.

Cleaning Wounds

According to MedCart, the salt in saline water imparts an antibacterial effect that makes it ideal for cleaning cuts and scrapes without causing additional pain. Unlike harsh antiseptics that might sting, the saline solution removes debris and dead skin cells while being gentle on healing tissue. A homemade saline solution for minor wounds can effectively clean the area before applying bandages or other treatments.

Cleaning Contact Lenses and Piercings

Saline water is also an excellent cleanser for contact lenses and new piercings. Dr. Nelli Gluzman explains that you can soak your reusable contact lenses in saline solution to ward off bacteria. “Given that contact lenses are very sensitive, it is important to use proper cleaning liquids that will not harm your eyes,” she notes.

Saline water also functions as an antiseptic for new piercings, as it helps draw out dead skin and other debris and impurities that might lead to the formation of crust or a trauma bump, Dr. Gluzman also points out. She recommends soaking your piercing in warm saline solution for five minutes once or twice a day to lower the risk of infection.

Salt in Softened Water: Should You Be Concerned?

As you’ve learned, desalination involves eliminating salt from water to create usable freshwater. But if you have water hardness problems at home, you might be concerned about water softeners adding sodium to the water or flushing it into the environment. This is understandable, especially if you are on a strict low-sodium diet or live in an area with restrictions on salt discharge into the environment. Or perhaps you would rather not have salt in your water.

If any of the above applies to you, there are ways to mitigate these concerns. First, you can install a reverse osmosis system to remove the sodium (and other contaminants) from the softened water. Alternatively, water conditioners like the Springwell FutureSoft® Salt-Free System require no salt or electricity to work nor release brine discharge into the environment. Instead, they use Template Assisted Crystallization (TAC) technology to transform hardness-causing minerals into harmless crystals that won’t stick to surfaces.

If you’re battling more than just hard water issues, Springwell has combined their whole-house filters with their salt-free conditioner into combo systems to address a broader range of water quality concerns. These dual-system “hybrid” setups provide cleaner, safer, better-tasting water for your entire household.

Learn more: The Difference Between Salt-Based and Salt-Free Water Softeners

Final Thoughts

As the global demand for freshwater surges, so does the need for innovative technologies like desalination. Factors from rising populations to climate change have left many countries facing the threat of water scarcity. Desalination, which involves removing the salt from seawater to produce drinking water, could make a huge difference. A global adoption of this technology could help ensure access to safe, potable water for billions of people, increase food security, limit droughts, reduce waterborne illnesses, and so on. However, this technology isn’t a magic pill; it alone can’t prevent a global water crisis. We must do our part to preserve our natural freshwater reserves for this and future generations.