Seawater Desalination: A Solution to Water Scarcity

Saad Iqbal—McMaster Molecular Biology & Genetics 2024

All living organisms on our planet require water to survive. Humans, plants, animals, and bacteria, would all perish without water. It is easy to believe that we will always have water, as water covers approximately 71% of the earth.¹ However, only 3% of the world’s water is fresh water that we need to drink, bathe in, and irrigate farm fields with, alongside other necessary uses. According to the World Wildlife Fund (WWF), by 2025 two thirds of the global population will face freshwater shortages. The most evident example of water shortage is the increasing frequency of droughts due to climate change.² Climate change is forcing us to find a solution quickly to prevent catastrophic water shortages in the near future. Some researchers suggest that the desalination of seawater into fresh water is a viable solution to our problem.

Desalination refers to the process of removing salts, minerals, and other contaminants from seawater in order to obtain fresh water. The two most common desalination techniques are thermal distillation and reverse osmosis.³ 

Thermal distillation is the process of boiling seawater. While the seawater is being boiled, it produces steam. This steam does not contain any of the salts or minerals from the seawater. The steam is collected, and then condensed to produce fresh water which we can then drink and use.³

SOURCE: Craig Refugio⁴

Another method of desalination is reverse osmosis, which relies on a membrane filtration system.In natural osmosis, water molecules move through a semipermeable membrane from a less concentrated solution into a more concentrated solution. However, in reverse osmosis the opposite occurs. Salt water is more concentrated than fresh water, water molecules will move away from the salt water, through the semi-permeable membrane. As the water molecules move through the semi-permeable membrane, the membrane traps salt and minerals on one side, creating fresh water on the other side of the membrane.³ The fresh water is then sterilized with ultraviolet light. As this method goes against natural osmosis, it requires extremely high amounts of pressure to push the water molecules through the membrane. 

SOURCE: BYJU’S ⁵

Although desalination is a possible solution to prevent future water shortages, there remain some lingering concerns. Desalination is currently one of the most expensive and energy intensive methods to obtain fresh water.³ As of today, most desalination factories use large amounts of fossil fuels, which contribute to increasing levels of greenhouse gases. Additionally, desalination has negative impacts on marine life. Desalination factories create a waste product known as brine. Brine is a solution of water containing extremely high concentrations of salt and chemical residues. Globally, approximately 155 million tons of brine is released into the ocean each day.³ The hyper-salinity of brine is toxic to marine animals and has the potential to dispirit ecosystems of the ocean.

However, there is hope on the horizon. Researchers are currently finding ways to improve desalination techniques, and solve some of these problems. For example, renewable energy sources such as solar energy and wind power are currently being explored and implemented in some desalination plants, which would limit the use of fossil fuels.⁶ Additionally, researchers are trying to limit the impact of brine. One suggestion is that brine can be converted into useful chemicals through an electrochemical process that forms sodium hydroxide, hydrogen, and hydrochloric acid.³

As researchers are actively attempting to reduce the problems associated with desalination, the process does have the potential to be an efficient way to produce fresh water in the future.

References

1. Water scarcity [Internet]. WWF. World Wildlife Fund; [cited 2022Nov28]. Available from: https://www.worldwildlife.org/threats/water-scarcity 
2. Horvatin J. By 2025, the World Wildlife Fund (WWF) estimates that two thirds of the global population may be facing water shortages. [Internet]. Aclarus Ozone // H2O Solved – Superior Water Treatment With Ozone. Aclarus Ozone // H2O Solved – Superior Water Treatment With Ozone; 2021 [cited 2022Nov28]. Available from: https://www.aclarusozone.com/did-you-know/by-2025-the-world-wildlife-fund-wwf-estimates-that-two-thirds-of-the-global-population-may-be-facing-water-shortages 
3. 26 RC|A, Cho R, Shown, Kathyhorsluvr@hotmail.com. A 1,000 year drought is hitting the west. could desalination be a solution? [Internet]. State of the Planet. 2022 [cited 2022Nov28]. Available from: https://news.climate.columbia.edu/2021/08/26/a-1000-year-drought-is-hitting-the-west-could-desalination-be-a-solution/ 
4. Reverse osmosis conditions | download table – researchgate [Internet]. ResearchGate.net. 2018 [cited 2022Nov28]. Available from: https://www.researchgate.net/figure/Reverse-osmosis-conditions_tbl2_268514267 
5. Raveendran B. Reverse osmosis (RO) – definition, principle, process, experiment, advantages, disadvantages with faqs on reverse osmosis. [Internet]. BYJUS. BYJU’S; 2022 [cited 2022Nov28]. Available from: https://byjus.com/chemistry/reverse-osmosis/ 
6. Singh R. Membrane Technology and engineering for water purification: Application, systems design and Operation. 2nd ed. Amsterdam: Butterworth-Heinemann; 2016.