Over time, there has been a significant increase in population throughout the world. However, at the same time, there has been a consistent decline in the sources of fresh water. In the face of such dire situations, many communities have begun to consider the use of desalination processes to offer fresh water when other treatment procedures and sources are not working. Actually, other procedures and sources may prove to adversely influence the environment and be uneconomical.
Desalination
Actually, desalination is a process that is capable of removing unsuitable minerals and excess salts from water. Typically, in most processes of desalination, there is a treatment of feed water and there is a production of two streams of water:
- Brine, which has high concentrations of salt and minerals
- Fresh water, which has low concentrations of minerals and salt
For desalination processes, feed water can be brackish water or seawater. Brackish water is known for containing more salt than drinkable water and less salt than actual salt water. Commonly, it can be obtained from estuaries, and the lower river courses.
It was in 1961 that an early desalination plant was developed and implemented in Freeport, Texas. It is worth noting that it produced approximately 1 million gallons regularly with the use of an LVT or long vertical tube distillation process for the production of water. With improvements in technology, two other vital processes such as membrane and thermal are becoming feasible options for the acquisition of fresh water from saline water.
In various areas around the world, especially in arid and densely populated areas, municipal water supplies rely on desalted water to a significant extent. In fact, it may be surprising to realize that it is utilized in over 120 nations. Moreover, approximately half of all the desalted water is developed and produced in North Africa and the Middle East.In various areas around the world, especially in arid and densely populated areas, municipal water supplies rely on desalted water to a significant extent. In fact, it may be surprising to realize that it is utilized in over 120 nations. Moreover, approximately half of all the desalted water is developed and produced in North Africa and the Middle East.
Most of the desalination plants in all countries are RO or reverse-osmosis systems.
Desalination Technologies
Primarily, there are two distillation techniques that are utilized throughout the world including membrane distillation and thermal distillation.
When it comes to thermal distillation technologies, they are used widely in the Middle East. It is generally because the petroleum reserves of the region play an important role in keeping the costs of energy low. In fact, the three large-scale and major thermal processes are VCD or vapor compression distillation, MED or multi-effect distillation, and MSF or multistage flash distillation. Solar distillation is yet another method but it is utilized for small production rates.
In different communities where intense sunlight and salt water are both prevalent, solar humidification as a simple technique can be used. Salt water is vaporized by the heat of the sun and the vapor is then condensed. The process is quite simple. However, in this process, the prime difficulty is there is a need for large land areas, and energy is required for water pumping.
Technologies of membrane distillation are utilized primarily in the US. Feed water is treated in these systems with the use of a pressure gradient for force-feeding the water through specific membranes. Moreover, the three important processes are RO or reverse osmosis, EDR or electrodialysis reversal, and ED or electro-dialysis (Curto, Franzitta, & Guercio, 2021).
Thermal Technologies
MSF: In general, multi-stage flash distillation is a comprehensive process that is used for transferring the saline feed water to different chambers. The water, in these chambers, is heated and compressed to high pressure and temperature. With the progressive passage of water through the chambers, there is a reduction in pressure which causes the water to boil. In each chamber, fresh water is produced from boiling and it is then condensed.
VCD: When it comes to vapor compression distillation, it can independently function and can be utilized in combination with other processes of thermal distillation. Commonly, VCD units are utilized for the production of fresh water for medium and small-scale purposes including petroleum drilling sites, industries, and resorts.
Solar Distillation: Generally, solar distillation is utilized for small operations. Even though the designs of these units tend to vary significantly, the fundamental principles remain the same. The saline water is evaporated by energy from sun. From the process of evaporation, the water vapor is then condensed on a clear plastic or glass covering, and then, fresh water is collected (Teow & Mohammad, 2019).
The covering is actually utilized for both transmitting radiant energy and enabling the condensation of water vapor on the interior surface. The unevaporated and salt water left behind creates the brine solution which needs to be discarded. This method is often considered and utilized in different arid regions with a lack of fresh water. In recent tests performed by Texas AgriLife Extension Service, it has been identified that solar still a surface area of only 7.5 square feet is capable of producing sufficient water for the survival of a person.
Membrane Technologies
Actually, a physical barrier is used by membrane desalination processes in the form of a membrane. It also relies on a driving force, which can be a pressure gradient or even an electrical potential. It is often required by membrane technologies that the water under physical and chemical pre-treatment for limiting blockage by the scale and debris development on the membrane surfaces.
ED and EDR: In electrodialysis reversal and electro-dialysis, the membranes used are created to allow the passage of either negatively or positively charged ions. In saline water, four common ionic molecules include carbonate, calcium, chloride, and sodium.
EDR and ED depend on an electrical potential for attracting and moving different anions or cations through a membrane. It serves to produce fresh water.
Reverse Osmosis: When it comes to RO or reverse osmosis, it utilizes a pressure gradient for moving feed water right through the membrane. All salt ions are prevented by it from passing.
Actually, there exist different membrane treatment processes such as microfiltration, ultrafiltration, and nanofiltration. In accordance with the type of process, pore sizes of membranes tend to vary.
Since there are small pores in the RO membrane, it is necessary for feed water to be adequately pretreated before it is passed through it. It is possible for the water to be pretreated physically and chemically for the prevention of suspended solids, scaling, and biological growth.
Water flow is ensured by the high-pressure feed through the membrane elements. Actually, the spiral RO membrane is developed in a spiral pattern which enables different alternative layers of brine spacing and feed water, a porous water carrier, and an RO membrane. Fresh water is allowed by the porous carrier to flow into the center to be collected in the water tube (Ghaffour, Missimer, & Amy, 2013).
Brine Management
What about the brine? Well, both membrane and thermal desalination processes tend to produce significant brine water. It is recognized for its high concentration of minerals and salt. It is worth noting that the brine needs to be disposed of in an environmental-friendly and economical manner.
Some options for brine discharge include evaporation and discharge into the ocean. There is no doubt that each option has both disadvantages and advantages. Regardless, it is necessary to ensure that the brine water influences aquifers and water bodies minimally.
Challenges
Even though these techniques are efficient, there are a number of challenges associated with their implementation. First of all, existing desalination technologies and methods need a significant amount of energy, typically through fossil fuels. Therefore, the process is highly costly and most communities are unable to actually afford it. Due to it, desalination is utilized only in those areas where fresh water sources are not prevalent economically.
Another major challenge associated with the existing technologies is the amount of brine wastewater and emissions of greenhouse gas by them. They pose a great environmental concern that needs to be addressed. Otherwise, the use of these techniques is capable of adversely influencing the environment to a significant extent.
A Modern Advancement
Recently, a portable desalination unit was developed by MIT researchers, which weighs below 10 kilograms. Still, it is capable of removing salts and particles for the generation of drinkable water.
It is just the size of a suitcase and needs less power than a cell phone charger to operate. In fact, it can even be powered by a portable and small solar panel that can be purchased online for approximately 50 dollars. Drinking water is automatically created by it which tends to exceed the quality standards of WHO or the World Health Organization. You may be surprised to know that its usage is so simple that it requires the push of only a single button.
In contrast with other portable devices that require the passage of water through filters, it uses electrical power for the removal of particles. Maintenance requirements are decreased to a significant extent by the elimination of the need for filter replacement.
Actually, it enables the unit to be considered and implemented in resource-limited and remote areas. It could even be considered for assisting and helping refugees who are escaping different natural disasters.
As it has been identified, commercial desalination units are not only costly but also need high-pressure pumps for pushing water through specific filters. Therefore, this unit does not consider and use the same mechanism. Instead, it utilizes a method called ICP or ion concentration polarization. The ICP process does not really filter water but uses an electrical field to different membranes that are placed below and above a channel of water.
Charged particles are repelled by membranes including viruses, bacteria, and molecules. In addition, the charged particles are funneled or passed into a stream of water, which is discharged eventually.
Both suspended and dissolved solids are removed by the process, which enables the water to effectively pass through the channel. Considering the fact that it requires only a low-pressure pump, less energy is used by ICP than any other technique.
However, since ICP is capable of always removing the floating salts, a second process was incorporated into the device in the form of electro-dialysis. It facilitates the removal of all salt ions.
A professor of computer science, electrical engineering, and biological engineering, Jongyoon Han, performed different tests on the device. The researchers even analyzed it at the Carson Beach of Boston and the device passed the tests efficiently. The water it produced effectively exceeded the quality standards of WHO.
In accordance with Han, the device had been successful in the very first run. In addition, a major challenge associated with designing and developing such a system has been creating an intuitive device that could be utilized and operated by anyone without experiencing difficulties.
Han is consistently working and focusing on making the device more user-friendly and easy. At the same time, he is also hoping to improve its production rate and energy efficiency through a startup that he is planning to launch.
Han is consistently working and focusing on making the device more user-friendly and easy. At the same time, he is also hoping to improve its production rate and energy efficiency through a startup that he is planning to launch.
Han determines that the materials can be quite expensive when tends to present a challenge. Still, this device is far more affordable, easier, and efficient than any other commercial technique or method available in the market.
Desalination Companies
Desalination is undoubtedly a critical aspect in which major companies around the world are investing. Some major companies consistently investing in the advancement of desalination technologies and methods include Suez, Doosan Heavy, Acciona, and Hitachi Zosen. These are some major companies that are actively researching and investing their resources in advancing desalination technologies. Moreover, these companies attempt to ensure that drinkable water can be produced to such an extent that people do not have to suffer anymore.
So, what does it mean? It means that desalination has acquired some significant attention from researchers and businesses around the world. Desalination methods ensure that drinkable water is produced through the treatment of salt water. Moreover, with time, desalination methods and techniques are being advanced by researchers. Han invented a portable desalination device that can be used by almost anyone. It requires lesser energy than any other commercial technique and is also more affordable. It presents a breakthrough in desalination techniques. It even urges researchers around the world to further advance desalination methods and make them more economical.
References
- Curto, D., Franzitta, V., & Guercio, A. (2021). A review of the water desalination technologies. Applied Sciences, 11(2).
- Ghaffour, N., Missimer, T. M., & Amy, G. L. (2013). Technical review and evaluation of the economics of water desalination: current and future challenges for better water supply sustainability. Desalination, 309, 197-207.
- Teow, Y. H., & Mohammad, A. W. (2019). New generation nanomaterials for water desalination: A review. Desalination, 451, 2-17.
