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Thesis: Fresh water is one of the most important resources that exists today, yet its quantities are very limited. Desalination technology provides a solution to a critical worldwide water scarcity problem, proven yet expensive and not fool-proof.

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Water Desalination

In researching nuclear energy while at Penn State 2 summers ago now, I came across the concept of water desalination. Water desalination seems to have been a discussion topic for years now, yet people don’t entirely know what it is, how it works, what the current state of desalination technology is, or what possibilities exist for the future.

So, today I’m here to add another article to the list about water desalination, but hopefully after this, you won’t feel the need to read more (or maybe you’ll want to learn even more and are about to dive in deep).

Let’s start at the beginning.

Credit Schilb Antiquarian

Q&A: Water Desalination Edition

Aristotle. It seems as though almost everything nowadays has evolved enough to have some tangential relation to Aristotle. Desalination, apparently, is no different.

In his treatise, Meteorology, Aristotle discussed principles he observed concerning air and water, parts of the Earth, weather, etc. Written in 340 B.C., Aristotle’s treatise is estimated to be the oldest comprehensive writing on the subject of meteorology.

In this treatise, Aristotle explains 2 main theories:

• The universe is spherical
• The Earth and Moon were composed of the four elements: water, earth, fire, and air.

While important, we don’t really care about those given our topic today. We do, however, care about the following writing:

“Salt water, when it turns to vapour, becomes sweet and the vapour does not form salt water again when it condenses.”

Unintentionally, Aristotle discovered and codified one of the foundational principles of water, the idea of evaporation, a forerunner for the concept we now call “desalination”.

What does desalination mean?

The United States Department of Energy explains desalination as the following:

“Desalination is the process of removing salts and other minerals from water, making it suitable for human consumption, irrigation, or industrial uses.”

Why is desalination important?

Water is one of the most precious resources on the planet. UNICEF cites that 4 billion people experience severe water scarcity for at least one month each year currently. That’s more than half the world’s population.

Water covers 70% of our planet, yet fresh water is only 3% of the total water on the Earth. Building on this, 2/3rds of this freshwater is in the form of ice or is otherwise inaccessible, meaning that 1% of total water is drinkable. It’s estimated that around 1.1 billion people do not have access to fresh water.

If we could figure out a way to cheaply and efficiently create more clean water, many of the current water scarcity needs could be met and many future problems could be prevented.

How does desalination work?

The goal of desalination, at least today, is to make seawater drinkable. That process is possible through a variety of different methods: boiling, reverse osmosis, solar distillation, electrodialysis, nanofiltration, and gas hydrate formation.

Most successful treatment options to desalinate water are either thermal desalination or membrane-based technologies, although other technologies are also under development.

The United States Department of Energy defines thermal desalination and membrane-based technologies as the following:

Thermal desalination systems heat water so that it evaporates into steam, leaving behind impurities, which then condenses back into a liquid for human use. Yet these phase changes (from liquid to steam and back to liquid) mean that thermal desalination is more energy intensive than modern membrane technologies. Some of the thermal energy applied to evaporate the water can be recovered as the steam condenses back into liquid water, but a significant amount of heat ends up being wasted.

Membrane-based desalination describes a class of technologies in which saline water passes through a semipermeable material that allows water through but holds back dissolved solids like salts.

Credit Bloomberg

What is brine?

Desalination’s goal is to remove any impurities from local water. This means one output is fresh water and the other is what’s left. What’s left is called brine.

Usually, brine is dumped back into the ocean. However, pumping highly concentrated salty chemicals can directly impact local marine life.

Desalination technology is constantly improving to maximize water recovery and reduce the volume of brine produced. The objective is to reach zero liquid and a complete solid output. This would limit the harmful effects on the marine environment as no brine would be released.

However, while brine is still liquid at this point, there are solutions being posed. Engineers at MIT have found that this brine can be turned into useful products through nanofiltration and electrodialysis to produce a desired end product. While this process isn’t new, the researchers did analyze and find a specific combination of products that could be produced with the most economic viability.

Credit 23ABC

What are the different types of desalination?

Boiling

The oldest form of desalination is boiling. The boiling method consists of boiling water in an evaporation device that collects the steam and then condenses it to obtain fresh water. This is the most obvious method for removing salt, but it isn’t the most effective since it consumes large amounts of energy.

Reverse Osmosis

Reverse osmosis refers to using semipermeable membranes to allow the water to pass through, but not the salt. It is the most used process to desalinate as it consumes less energy than the rest. These membranes are made of ultra-thin polyamide which can become contaminated with bacteria so the water must be treated.

Solar Distillation

Solar distillation refers to evaporating seawater in large facilities with roofs where it is condensed and collected as fresh water. Although the energy used is the sun’s heat, making energy intake minimal, large areas of land and large facilities are required.

Electrodialysis

Electrodialysis refers to moving salt water through electrically charged membranes that trap the salt ions dissolved in salt water.

Nanofiltration

Nanofiltration uses nanotube membranes similar to reverse osmosis membranes yet that have higher permeability which allows more water to be processed. These membranes are manufactured with sulfonated compounds which eliminate traces of pollutants.

Gas Hydrate Formation

Gas hydrates are crystals that are formed by combining water with gas at high pressure and at a low temperature. During this process, the salts and impurities present in the water disappear. As the temperature increases, the gas is able to be recovered and separated, leaving fresh water.

Multi-Stage Flash Distillation

Multi-stage flash distillation is a thermal desalination process that leverages staged vacuum pressure chambers to evaporate and condense water into freshwater while leaving behind remaining brine waste streams.

Multiple Effect Distillation

Multiple effect distillation uses a series of stages where water is heated by steam in tubes then evaporated and fed into more tubes and the effects are continuously repeated. Each stage reuses the energy from the previous stage.

Vapor Compression Distillation

Vapor compression distillation is an evaporation method by which a blower, compressor, or jet ejector is used to compress water into vapor. The vapor is then recondensed into freshwater, leaving brine behind.

Freezing

Freezing is an emerging technology where cryogenic means freezing seawater to form pure ice crystals. These crystals become separated from the residual brines. When melted, they produce fresh water.

Credit IDE Technologies

Does desalination work today?

Short answer, yes. The United Nations recently completed a survey that counted approximately 16,000 desalination plants currently in operation across the globe, spread throughout 177 countries.

The top 5 countries estimated to produce the most desalinated water are Saudi Arabia, Kuwait, Algeria, Israel, and Australia.

Some of the current applications of desalination technology are the following:

• Oil Tankers
• Coastal Developments
• Work Boats
• Island-Based Businesses
• Hotels & Resorts
• Fish Processing Plants
• Villages & Cities
• Seaside Work Sites
• Seaside Villas
• Cargo Ships

Credit Musica Project

Pros of Desalination

Pro #1: Desalination increases water security. This can be extremely important in regions that have significant water scarcity.

Pro #2: Desalination can create a source of water closer to the demand. Desalination can make communities less reliant on distant sources of water, instead bringing the source closer to the demand. This can be especially important to rural and underserved communities.

Pro #3: Desalination technology can be applied to a variety of different issues. For instance, desalination plants can create water for agricultural irrigation or industrial processes. These technologies aren’t just useful for creating fresh drinking water.

Pro #4: Desalination plants are able to produce a steady supply of clean water year-round. This is especially important for regions with seasonal variability in their water cycles.

Pro #5: Mobile desalination plants can assist during droughts or natural disasters. By creating desalination plants capable of moving to where the water needs are greatest, these plants can help solve problems more immediately than other solutions, especially if local infrastructure is damaged.

Pro #6: As the ocean is the source of seawater, desalination plants have a virtually unlimited supply, meaning that input costs are lowered and a steady supply can be estimated.

Credit Green Synergy Engineering

Cons of Desalination

Con #1: Desalination processes require large amounts of energy. Removing salt and other chemicals from water is highly energy-intensive, especially for the value of the output. However, continual technology advancements have pushed the energy demand lower and lower, making desalination a more effective solution.

Con #2: Desalination processes require large amounts of infrastructure.

Con #3: As mentioned before, at this point, desalination processes still create brine output which can be harmful to the local environment and marine life.

Con #4: Desalination isn’t exactly cheap. High amounts of infrastructure investment and capital are needed to create a desalination plant. Technological developments continue to push down this cost to make it more effective, but this favors certain desalination methods over others.

What will the water desalination market look like in the future?

Many industry reports estimate the desalination market to double in the next decade. As groundwater levels continue to decline and the demand for freshwater for homes and industrial requirements increases, the water desalination market has the opportunity to fulfill this need.

In the short term, as the supply of water desalination plants continues to increase, I would still expect to see rising prices of water to incentivize people to use less.

Furthermore, governments are projected to begin heavy investment into national desalination programs–and some, like Saudi Arabia, have already begun.

Credit Deposit Photos

Takeaways

Benjamin Franklin once said:

“When the well is dry, we know the worth of water.”

The amount of water on this Earth is finite. Even more so, the amount of freshwater available is majorly finite. Countries, cities, and individual people are starting to feel this scarcity.

In the 21st century, water has increasingly become a valuable commodity. The countries that have it prosper. Those without feel immense strain.

Yet, solutions are possible. Desalination technology works. There is a way to create more freshwater where there isn’t any. However, desalination technology isn’t cheap.

As the well continues to be used, the worth of water is increasingly becoming known.

That doesn’t mean all hope is lost. Solutions exist, however, they may not be in the form we would prefer them in.

At this point, every drop matters. Use it wisely, with the understanding that others don’t even have the option to have water.

Anywho, that’s all for today.

-Drew Jackson