What if there was enough freshwater worldwide? Desalination is already the key to make it happens. However, it is an expensive process, not to mention it impacts the marine environment as well. How to solve these issues? Keep reading.
Seawater desalination has the potential to reliably produce enough potable water to support large populations!
The abundance of potable water or so-called freshwater implies sufficient quantities not only for domestic consumption but also for commercial and industrial processes.
What is the difference between freshwater and tap water?
The term "freshwater" usually refers to water that isn't salty, to distinguish it from seawater. On the other hand, "tap water" in the United States is usually purified and disinfected water.
The world's freshwater shortage tends to increase as its population grows exponentially. Therefore, creating new desalination techniques at a lower cost than the current ones and with less damage to the marine environment is paramount.
Of the Earth's 71% surface, 97.4% is seawater and only 2.6% freshwater.
What is desalination?
Technically speaking, desalination is a technique that allows the excess of mineral salts, microorganisms, and other solid particles from seawater or brackish water, to obtain freshwater for consumption.
Meet the 4 desalination processes:
Reverse Osmosis: a process that splits distinct substances through a membrane that retains the solute. Water passes through a semipermeable membrane, endorsed with microscopic pores, responsible for retaining salts, microorganisms, and other impurities. Thus, the liquid is parted from the salt solution, becoming freshwater.
Multistage distillation: in this method, high-temperature steam is used to make seawater boil. Seawater itself is used as a condenser of water that is evaporated. This ensures a high degree of purity.
Freezing: As the seawater is brackish, it is freezing/thawing produces pure, unsalted ice. This very technique is still under testing. There are proposals for the exploration of polar ice caps, where much of the freshwater on the planet is located.
Thermal desalination: the most widely used technique is called "solar distillation" - used mainly in hot places - which is the construction of large tanks covered with glass. Sunlight passes through the glass and the water from the raw liquid evaporates, turning into freshwater. In cold places, desalination by solar energy is the best option, because it is cheap and sustainable since it does not consume resources such as oil and coal.
Solar energy can replace other desalination techniques with low-cost causes, as suggested in a statement from Monash University in Melbourne, Australia.
A new process is upcoming: the solvent desalination technique
Engineers from Columbia University in the USA have developed this new solvent desalination technique that can solve the issue of brines that have a very high degree of salinity.
The new technique, also known as "solvent extraction with oscillating temperature", absorbs water using a solvent and does not use membranes in the evaporative phase.
"Zero liquid discharge is the last frontier of desalination," stated Professor Ngai Yip. "Evaporating and condensing water is the current practice of this technique by the solvent. We've been able to reach it without boiling the water - this is a breakthrough to desalinate ultra-high salinity brines, which demonstrates how our technique can be a transformative technology for the global water industry."
In other words, the method consists of extracting all water from the brine into the solvent, resulting in precipitation of the salts when all the water is "sucked" by it. So salts from solid crystals are deposited at the bottom, from where they can be easily sifted.
Another advantage of the solvent desalination technique
This process also allows to be used for other high salinity brines, such as so-called "return water" or return flow, which is water produced during the extraction of oil and gas, waste from steam-fired power plants, discharges from coal installations and landfills.
Despite the still high cost, there are currently 7,500 desalination plants in regions such as:
Guernsey (one off the Channel Islands in the English Channel)
These countries convert more than 4.8 billion cubic meters/year of saltwater into freshwater! The Maldives, Malta, and the Bahamas meet all their drinking water consumption needs, exclusively through desalination.
The dark side of desalination
Desalination can cause damage to marine life because the by-products generated by desalination make seawater bolder and therefore more toxic.
That is, for each gallon of produced freshwater, it generates other polluted substances full of chlorine and copper. When pumped back into the ocean, this toxic brackish liquid decreases the volume of oxygen in the water and has an impact on organisms along the food chain.