Yes, is there a way to make salt water drinkable? Methods and Dangers Explained

Over 97% of Earth's water is saline, making freshwater a limited resource for more than 40% of the global population. So, is there a way to make salt water drinkable? Fortunately, the answer is yes, through a process called desalination, which can be achieved through various high-tech and rudimentary methods.

Quick Summary

Salt water can be desalinated to produce potable water, a process used commercially and in survival scenarios. Methods include thermal distillation, reverse osmosis membrane filtration, and solar stills, each with its own advantages.

Key Points

• Desalination is Possible: Salt water can be converted into safe drinking water using processes that remove salt and other impurities.

• Boiling Alone is Not Enough: Simply boiling salt water kills bacteria but does not remove salt, making it unsafe to drink.

• Distillation is a Key Method: By evaporating water and collecting the condensation, distillation separates pure water from salt.

• Reverse Osmosis is an Energy-Efficient Alternative: Large-scale reverse osmosis uses membranes and high pressure to separate salt from water, consuming less energy than traditional distillation.

• DIY Survival Options Exist: A solar still, using evaporation and condensation powered by the sun, is a viable, albeit slow, method for making small amounts of water drinkable in an emergency.

• Drinking Salt Water is Extremely Dangerous: Consuming unprocessed salt water causes severe dehydration, electrolyte imbalance, and puts immense strain on the kidneys.

Why Drinking Unprocessed Salt Water is Dangerous

Consuming unprocessed salt water is extremely dangerous and can lead to severe dehydration and potentially fatal health complications. The human body is designed to maintain a delicate balance of electrolytes, and the high concentration of sodium in seawater disrupts this equilibrium.

When you drink saltwater, your kidneys must work harder to filter out the excess salt. To do this, they require water from your body's cells and tissues, leading to a net loss of hydration. This can trigger a range of adverse effects:

• Increased Dehydration: You lose more water trying to flush out the salt than you ingest.
• Kidney Strain: The intense effort required to process the high salt content can damage your kidneys over time.
• Nausea and Vomiting: The body's rejection of the excessive salt leads to fluid loss through vomiting, worsening dehydration.
• Electrolyte Imbalances: Elevated sodium levels can cause irregular heart rhythms, muscle spasms, and neurological problems.

Industrial Desalination Methods

Large-scale desalination is a global industry, with over 21,000 plants operating worldwide to supply water for municipalities, industry, and agriculture. The two most prominent technologies are multi-stage flash (MSF) distillation and reverse osmosis (RO).

Reverse Osmosis (RO)

Reverse osmosis has become the most widely used and energy-efficient desalination method, relying on membrane technology. This process works by forcing saline water under high pressure through a semi-permeable membrane. The membrane's pores are so fine that they allow water molecules to pass through while blocking the larger salt molecules and other impurities.

RO systems typically involve several steps:

1. Intake and Pre-treatment: Water is drawn and pre-filtered to remove large solids and organic matter, preventing membrane damage.
2. High-Pressure Pumping: Pumps increase the water's pressure to overcome natural osmotic pressure.
3. Membrane Filtration: Pressurized water is pushed through the RO membranes, separating fresh water (permeate) from concentrated brine.
4. Post-treatment: The freshwater is remineralized and disinfected to meet drinking water standards.
5. Brine Disposal: The leftover brine is disposed of safely, often through dilution in the ocean, to minimize environmental impact.

Multi-Stage Flash (MSF) Distillation

MSF is a thermal desalination process where saline water is heated and then evaporated in a series of chambers (stages) with progressively lower pressure. As the water enters each stage, the lower pressure causes it to rapidly boil and "flash" into steam. This steam is then condensed into fresh water. MSF is highly effective but also more energy-intensive than RO, though it can treat water with very high salinity.

Simple DIY Desalination for Survival

While industrial methods are complex, individuals can create small-scale desalination devices in a survival situation using basic principles of evaporation and condensation.

The Solar Still

A solar still is a passive method that mimics the Earth's natural water cycle. It is effective but produces water very slowly.

To build a basic solar still:

1. Dig a hole and place a watertight container (like a cup) in the center.
2. Fill the space around the container with saltwater, keeping the cup's rim above the water level.
3. Cover the hole with a clear plastic sheet, securing the edges with soil or rocks.
4. Place a small rock or weight in the center of the plastic, directly over the cup, to create a low point.
5. The sun heats the saltwater, causing it to evaporate. The resulting vapor condenses on the underside of the plastic, drips from the low point, and collects in the cup as fresh water.

Boiling and Condensation (Stovetop Method)

For a quicker process, boiling and collecting steam is a more direct form of distillation, but it requires a heat source.

This method involves:

1. Placing a smaller, heat-safe cup in the center of a larger pot.
2. Filling the pot with saltwater, ensuring the water level is below the top of the inner cup.
3. Inverting the pot's lid and placing it on top, with the handle pointed down toward the cup.
4. Boiling the water gently. The steam rises, condenses on the cooler lid, and drips into the inner cup.

Distillation vs. Reverse Osmosis Comparison

Feature	Distillation (Thermal)	Reverse Osmosis (Membrane)
Mechanism	Boiling water, collecting condensed vapor.	Forcing water through a semi-permeable membrane under high pressure.
Energy Use	High (requires heating water to boiling point).	Lower (relies on pressure, not heat).
Purity	Produces very high-purity water, removing nearly all contaminants.	Highly effective, removing most salts and contaminants.
Speed	Can be slower for large volumes due to heating and cooling time.	Generally faster than distillation for large-scale production.
Cost (Industrial)	More expensive due to high energy consumption.	More cost-effective for large-scale operations and improving efficiency.
Wastewater	Produces some residue in the boiling chamber.	Generates a significant amount of concentrated brine wastewater.
DIY Method	Relatively simple with basic containers and heat source.	Requires a high-pressure system and specialized membranes.

Conclusion

Yes, it is possible to make salt water drinkable through various desalination methods, both on an industrial scale and in a survival context. The key is to separate the water from the dissolved salt, typically through distillation or reverse osmosis. Drinking unprocessed salt water is highly dangerous and worsens dehydration due to the strain it places on the kidneys. While industrial-level technology provides a sustainable solution for water-scarce areas, simple DIY methods can be life-saving in an emergency. Understanding these processes is not only valuable knowledge for survival but also highlights the innovative solutions used to combat global water scarcity. For a deeper understanding of the processes and history of desalination, see the Wikipedia page on the topic.

Future of Desalination

Technological advancements continue to make desalination more efficient and sustainable. Research is focused on reducing energy consumption and managing the brine byproduct, which is a significant environmental concern. Innovations include improved membranes, renewable energy coupling, and resource recovery from the brine itself, offering a promising outlook for future freshwater production.

Frequently Asked Questions

Is it safe to drink salt water if boiled?

No, boiling salt water makes it sterile by killing germs, but it does not remove the dissolved salt. The salt content will become even more concentrated as some of the water boils away, making it unsafe and more dehydrating to drink.

Can a regular water filter purify salt water?

No, a standard water filter, like those using activated carbon, cannot remove dissolved salt from water. The salt molecules are too small to be caught by the filter's pores. Specialized membranes, like those used in reverse osmosis, are required.

How do large ships and submarines make their own drinking water?

Many large vessels, including navy ships and submarines, use desalination equipment. This often involves either low-pressure evaporators that use waste heat to create distilled water or reverse osmosis systems.

What is the most common method for large-scale desalination?

Reverse osmosis (RO) is currently the most widely used and energy-efficient method for large-scale desalination globally. It is used in large plants to produce clean, potable water for cities and industries.

Does desalinated water taste different?

Yes, desalinated water can sometimes taste different from natural fresh water because the process removes all dissolved minerals. Some desalination plants add minerals back during post-treatment to improve the taste and meet health standards.

Can you use a simple solar still to make water drinkable?

Yes, a simple solar still, constructed from a hole in the ground, a container, and a plastic sheet, can be used to desalinate water in a survival situation. However, it is a very slow process and produces a small amount of water.

What happens to the excess salt after desalination?

The excess salt is concentrated into a liquid called brine. This brine is typically returned to the ocean via an outfall and diffuser system that rapidly mixes and dilutes it to minimize environmental impact.