The Scarcity of Freshwater on Earth
Only 3% of the Earth’s water is fresh, with the majority being inaccessible—trapped in glaciers, polar ice caps, the atmosphere, or soil. Some freshwater sources are highly polluted or too deep underground to be affordably extracted. In contrast, 97% of Earth’s water resides in the oceans. This leads to the question: if we could use ocean water for drinking, wouldn’t it solve our water shortage problem? So, why can’t we drink ocean water? While desalination processes exist, there are reasons why we can’t simply rely on them for drinking water.
Understanding Sodium and Its Effects
Sodium, a mineral and a component of salt, is essential for our bodies in small amounts but harmful in excess. Although people can’t drink saline water directly, desalination can convert it into freshwater.
What is Saline Water?
Saline water contains significant amounts of dissolved salts. The concentration of these salts is measured in parts per million (ppm). For instance, water with a salt concentration of 10,000 ppm has 1% of its weight from dissolved salts.
What Happens If You Drink Salt Water?
Drinking salt water can severely impact your body in multiple ways. When you ingest large quantities of salt, your cells lose water through osmosis, causing them to shrink. This condition, known as hypernatremia, results from a rise in sodium concentration in the blood. Severe hypernatremia can lead to confusion, muscle twitching, seizures, coma, and death. If untreated, acute hypernatremia can cause permanent brain damage. High sodium intake can also elevate blood pressure, harm kidneys, and increase the risk of cardiovascular disease.
While sodium is beneficial in small amounts—it helps reduce inflammation, aids digestion, and promotes healthy bones—most people already get sufficient sodium from their diet. Therefore, drinking salt water is both unnecessary and potentially harmful. Ocean water has a salt concentration four times higher than that of the human body. Human kidneys can only produce urine that is less salty than ocean water. To eliminate the excess salt consumed by drinking ocean water, you would need to urinate more water than you drank, eventually leading to dehydration and death. Excessive sodium intake can also cause muscle weakness, restlessness, extreme thirst, and irritability.
Understanding Reverse Osmosis: A Solution for Desalination
Reverse osmosis (RO) is a water treatment process that transforms saline water into fresh water by pushing it through a filter membrane. This method utilises a pressure gradient to force high-pressure saltwater feed through a membrane, effectively filtering out chlorine, salt, and dirt. RO desalination relies on the principle of osmosis, transferring water through a series of semi-permeable membranes to remove salt and other impurities.
The Principle of Osmosis
Osmosis is a fundamental, natural process that occurs both around and within us, playing a crucial role in regulating cell functions and maintaining water balance in our bodies. In reverse osmosis, this natural process is synthetically harnessed to separate heavier particles from lighter ones. When saline water is forced through a semi-permeable membrane, the heavier salt particles remain on one side while the lighter water molecules pass through to the other side.
Conclusion
Reverse osmosis is a powerful tool for desalination, providing a viable solution for producing fresh water from saline sources. Despite its efficiency challenges, RO remains a widely used method for ensuring access to clean drinking water, both at home, on boats/yachts/shops and in large-scale water treatment facilities.