Desalination could solve the global water crisis, but the method comes with environmental effects. We will explain this in this article in detail.
In the past few decades, the world has experienced rapid population growth, which has placed more pressure on the Earth’s natural resources, including naturally occurring freshwater. Sadly, 1 out of 9 individuals lacks ready accessibility to safe drinking water. If freshwater’s current global consumption rate is consistent, the global water demand will be 40% greater than the water supply in less than ten years. It’s a rather disturbing statistic.
Global water scarcity or water stress has been an issue for quite a while now. Freshwater that’s easily accessible only makes up a meager 0.7% of the Earth’s water resources. On the other hand, saltwater makes up a vast majority of the Earth’s water availability, up to 96.5%. Hence, we need to realize that desalination can solve the global issue of water shortage.
So, what is desalination?
The Concept of Desalination
In simple terms, desalination is converting saltwater (seawater or brackish water) into freshwater. Thus, desalination is a process of water treatment that involves stripping seawater of its mineral components. Desalination treats and processes any type of saltwater to produce clean water that is wholesome for human use or consumption.
Desalination produces two things from saltwater- freshwater, and brine. It’s adopted as a water treatment process on several submarines and ships.
For a long time, the world primarily depended on rainfall as a source of freshwater, but perhaps it’s time for desalination to gather more interest, just like wastewater treatment. It’s a cost-effective method of producing fresh water and rectifying water stress for the global population.
Desalination is energy-intensive, making the process more costly than sourcing freshwater through water conservation, wastewater reuse, groundwater, and surface water. These alternative sources of freshwater are not constantly there to give us access to safe water, plus the fact that water reserves around the world are quickly diminishing.
The desalination process occurs in different forms.
Types of Desalination
The most popular types of desalination are distillation (thermal-based desalination) and reverse osmosis (membrane-based desalination). Distillation has various forms.
This distillation process utilizes solar energy to heat salt water to the point that it triggers the water to evaporate. After the process of evaporation, the vapor which has been trapped will condense on a surface. This is the natural process.
The artificial application of solar distillation involves photovoltaic cells, which convert solar energy to electricity to power the desalination process.
This distillation process involves reducing atmospheric pressure, which will trigger the reduction in temperature needed to make water evaporate or vaporize.
The water reaches a boiling point when the vapor pressure is equivalent to the ambient pressure. Vapor pressure rises in parallel with the temperature. This means that the higher the temperature, the stronger the vapor pressure and vice versa.
Water can also reach a boiling point when the ambient atmospheric pressure is lower than typical. This reduction in pressure allows for the utilization of low-temperature heat from electricity or industrial processes.
Multi-Stage Flash Distillation
This process involves the evaporation and separation of seawater through serial flash evaporations. Every subsequent flash evaporation process uses the released energy from the condensation of the vapor in the previous flash evaporation process.
This distillation process utilizes temperature differences throughout a membrane to vapourize saltwater and, eventually, condense the freshwater on the cooler side of the membrane. The membrane is designed to be very efficient and durable.
According to a study, a membrane that was manufactured using co-axial electrospinning of PVDF-HFP and silica aerogel could filter up to 99.9% of salt from saltwater after consistent usage for 30 days.
Reverse Osmosis Desalination
Reverse osmosis is the most popular desalination process in the world in regard to annual growth and installed capacity.
The reverse osmosis desalination process utilizes several semipermeable membranes and artificial pressure to force water supply through the membrane to trigger water permeation.
So while water permeates the membrane through to the other side, salt is retained on the opposite side. As a result, reverse osmosis desalination is more energy-efficient than thermal desalination.
The amount of energy needed to power a desalination process is hinged on factors such as the volume of brine in the water, the size or capacity of the desalination plant, and the type of desalination process involved.
Currently, saltwater desalination is more expensive than conventional water sources, but with time, it is predicted that such costs will lessen as desalination technologies continue to improve.
Such improvements will trigger enhanced efficiency of energy, better plant optimization and operation, enhanced feed water pretreatment, and less expensive energy sources.
History of Desalination
Desalination dated back a long time ago. It has been regarded as a limited practice and concept. Ancient philosopher Aristotle made observations that saltwater became sweet when it turned into vapor and that the vapor didn’t condense back into saltwater again.
He also observed that a vessel of fine wax could hold clean water if immersed for a certain amount of time in saltwater. This is because the vessel acts as a membrane to filter out salt from the basic water.
There have been several experiments in desalination all through the Middle Ages, but it was never practical for industrial applications until this modern period. A fine example of a desalination experiment is Da Vinci’s observations in Florence in the year 1452. He found out that large quantities of saltwater can be distilled by boiling.
According to speculations, the first desalination plant constructed as an urgent matter was on an island close to Tunisia in 1560. The belief is that a troop of about 700 soldiers from Spain laid siege on the Turks. During the siege, the captain of the troop made an apparatus that could produce up to 40 barrels of fresh water daily.
Before the era of the Industrial Revolution, desalination was a foremost concern for ships on the sea, which needed ample stock of fresh water on board. Sir Richard Hawkins was a frequent traveler to the South Seas, and he said that during his travels, he was able to provide fresh water for his men through shipboard distillation.
Also, several popular figures of the 1600s, such as Walter Raleigh and Francis Bacon, produced publications on water desalination.
The Potential of Desalination in Alleviating Water Stress or Water Shortage
According to WHO (World Health Organization), half of the world’s population will be living in water-stressed countries by 2025.
Climate change has been pegged as one of the major causes of global water stress and intense water scarcity. Desalination can be recommended to alleviate water stress and aid over 2.4 billion people who lack access to safe water. Desalination happens to be a source of fresh water that’s independent.
Due to the vastness and sheer size of saltwater bodies, desalination will surely be a sustainable source of safe drinking water. It will be highly beneficial to regions where good health is a luxury because of contaminated water and the lack of water systems.
Desalination as an alternative helps sustainable water management and can keep up with the current wave of population growth. As a result, there will be less reliance on naturally occurring freshwater sources that climate change can influence or affect.
With desalination, water scarcity will no longer be a significant issue and the global water crisis could be solved. But why are we not using it already to prevent the global water crisis?
This video will help you to understand:
Limitations of Desalination
The world stands to gain from desalination, which doesn’t rely on climate change to make freshwater available. However, it has its demerits as well. The limitations of the desalination process include:
Disposal of Waste
Desalination, just like other water processes, has by-products. Desalination involves using purification chemicals to pre-treat the feed water before desalting it to make the process more effective. Such chemicals include hydrochloric acid, hydrogen peroxide, and chlorine, and their usage only covers a certain amount of time.
When these chemicals are no longer potent in cleaning the water, they are disposed of, which constitutes a significant environmental issue.
Human factors such as the disposal of chemical substances used in treating saltwater are a problem because they eventually get absorbed by the soil or find their way back to water bodies, endangering aquatic and plant life.
The Issue of Brine
Brine accumulation is another side effect of the desalination process. After the salt and water have been separated, an intense concentration of salt is left behind. One has to dispose of that.
Nearly all desalination plants return brine to its source- the ocean. This results in another environmental problem. Aquatic life can be critically endangered because they can’t adapt to the enhanced level of salinity in the water.
The injection of highly concentrated brine into the ocean can lower the water’s oxygen levels, triggering the suffocation of ocean plants and animals.
Desalination plants are still tentative water sanitation systems, and there’s no guarantee that desalinated water is safe to consume. In addition, the chemicals used in pre-treating the desalinated water can find their way into the finished product, thereby contaminating the water and endangering the consumers’ health.
It’s even more disturbing that desalinated water can be acidic to the digestive system and water pipes.
Aquatic Life Population
The forms of aquatic life most affected by the discharge of chemicals and brine desalination plants include Phytoplankton and Plankton, which is the base of the aquatic food chain. In other words, they are the essential element in the survival of all forms of marine life.
The operations of desalination plants can negatively impact the ocean population, not just the output but also the input. While collecting ocean water for desalination, the aquatic plants capture and kill the animals, other plants, and even eggs, a good number of which are offsprings of endangered species.
Desalination plants require a massive influx of energy to operate. This is particularly not helpful in a time where energy is more precious.
Causes of Water Scarcity
Water shortage is not experienced in every part of the world, at least not yet, but it is an issue in many countries. The major causes of water scarcity include:
In this present era, people are becoming less prudent with water. They use more water than they need because it’s available. In some cases, this overuse of water extends to animals and even land. In addition, water can be used for recreational purposes without any thought to the effect on the environment.
This phenomenon occurs when the atmospheric temperature rises and causes water from the various water bodies to evaporate more often, leading to the depletion of some rivers or lakes.
People residing in coastal areas are more affected by global warming than others due to water shortage when their river or lake dries up. In some cases, it is usually their only freshwater source.
Drought is one of the natural disasters characterized by the absence or inadequacy of rainfall, and it is commonly experienced in desert regions. When there’s not enough rainfall, one can hardly sustain life in the region.
Water pollution is one of the primary reasons for water shortage. This is a water shortage because there is water, but it’s very unwholesome, and usage or consumption can have adverse effects. Water can get polluted through the use of fertilizers, chemicals, feces, oil, corpses, and others.
A Glimpse into Cape Town
Cape Town is a city in South Africa. For some time now, the city has been plagued with serious water shortages. The primary reason for this is the decline in dam water levels, which has been on since 2015.
The water shortage issue in Cape Town peaked between 2017 and 2018 when the availability of water ranged between 15%-30% of the full dam capacity. As a result, Cape Town had to implement water regulations to mitigate the shortage. They succeeded in restricting water usage by more than 50% per day.
Desalination could solve the global water crisis but at a considerable cost.