Water scarcity is a growing issue across the globe, with millions of people lacking access to clean, safe water. The problem is exacerbated by population growth, climate change, and aging infrastructure.
Water is the most precious resource for sustaining life and survival of living world, but we are losing fresh water at an astonishing rate: Climate change is resulting in disappearing of glaciers and severe droughts, groundwater being pumped out faster than natural processes can replace it. Much of the world faces a hotter and drier future under climate change, according to scientists. Rainfall – including the monsoons that fortify agriculture in south Asia – will become more unpredictable. Storm surges could contaminate freshwater reservoirs.
The Overall global water demand is projected to increase by 55 percent on the way to 2050 led by countries like Brazil, Russia, India, Indonesia and China (BRIICS) to satisfy the needs of ever-growing population —a staggering 9.6 billion people by 2050. In countries like China, the largest growth rate in water use will be in the industrial and domestic sectors according to the Water Resources Group. And new fault lines are emerging with energy production. America’s oil and gas rush is putting growing demands on a water supply already under pressure from drought and growing populations.
Water scarcity is a major challenge facing the world today, with millions of people lacking access to clean water. Desalination – the process of removing salt and other minerals from seawater – is emerging as an increasingly important solution to this challenge. In this article, we explore the role of desalination in ensuring water security and the challenges and benefits of this technology.
Desalination has been used for centuries, but technological advances in recent years have made the process more efficient and cost-effective.
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There are two main types of desalination: thermal and membrane. Thermal desalination involves heating seawater to produce steam, which is then condensed to create freshwater. Membrane desalination involves filtering saltwater through a semi-permeable membrane to remove the salt and other minerals.
Some of the most common desalination technologies are reverse osmosis, distillation, and electrodialysis.
Reverse osmosis is the most common desalination technology. It uses membranes to filter out salt and other impurities from water. The membranes are made of a material that allows water molecules to pass through, but not salt molecules. The water is forced through the membranes under high pressure, and the salt is left behind.
Reverse osmosis is a very effective way to remove salt from water, but it is also an energy-intensive process. The high pressure required to force the water through the membranes requires a lot of energy.
Distillation is another common desalination technology. It uses heat to evaporate water and then condense it back into a pure liquid. The salt is left behind in the evaporated water.
Distillation is a very effective way to remove salt from water, but it is also an energy-intensive process. The heat required to evaporate the water requires a lot of energy.
Electrodialysis is a less common desalination technology. It uses an electric current to separate salt from water. The water is passed between two sets of electrodes, and the salt is attracted to the electrodes and removed from the water.
Electrodialysis is a less energy-intensive process than reverse osmosis and distillation, but it is not as effective at removing salt from water.
Other desalination technologies
There are a number of other desalination technologies that are being developed, including membrane distillation, forward osmosis, and capacitive deionization. These technologies are still in the early stages of development, but they have the potential to be more efficient and less energy-intensive than traditional desalination technologies.
Advantages of desalination
Desalination can provide a reliable source of freshwater in regions where traditional water sources are scarce or contaminated. In coastal regions where seawater is abundant, desalination can provide a sustainable source of freshwater. It can also help reduce reliance on finite freshwater resources such as aquifers and rivers, which are becoming increasingly depleted.
- Desalination can provide a source of fresh water in areas that are facing water shortages. This is especially important in areas that are located in arid or semi-arid regions, where freshwater is scarce.
- Desalination can help to reduce the demand for freshwater from other sources, such as rivers and lakes. This can help to protect these natural resources from overuse.
- Desalination can be used to produce high-quality water for drinking, bathing, and irrigation. The water produced by desalination plants is typically of very high quality and can be used for a variety of purposes.
- Desalination can help to protect the environment by reducing the need to extract freshwater from natural sources. This can help to reduce the impact of water extraction on the environment, such as the depletion of aquifers and the degradation of wetlands.
Disadvantages of desalination
While desalination has many benefits, it also presents several challenges. The primary challenge is cost. Desalination is an expensive process, and the cost of building and operating desalination plants can be prohibitive. Additionally, the high energy requirements of desalination can make it a carbon-intensive process. The environmental impact of discharging the brine produced by desalination is also a concern, as the brine can contain high concentrations of salt and other minerals that can harm marine ecosystems.
- Desalination is a relatively expensive process. The cost of desalination plants and the energy required to operate them can be high.
- Desalination is an energy-intensive process. The energy required to operate desalination plants can come from a variety of sources, including fossil fuels, nuclear power, and renewable energy. However, all of these sources of energy have their own environmental impacts.
- Desalination can produce brine, which is a concentrated salt solution that can be harmful to the environment if it is not properly disposed of. Brine can be discharged into the ocean, where it can harm marine life. It can also be stored in evaporation ponds, where it can take up valuable land and release greenhouse gases into the atmosphere.
- Desalination can hurt marine life if it is not done carefully. The construction of desalination plants can disrupt marine habitats and the discharge of brine can harm marine life.
Recent Advancements in Water Desalination
There have been a number of recent advancements in water desalination technologies. These advancements have made desalination more efficient, less expensive, and more environmentally friendly.
One of the most significant recent advancements in desalination is the development of membrane distillation (MD) technology. MD is a process that uses membranes to separate water from contaminants. The membranes are made of a material that allows water molecules to pass through, but not salt molecules. The water is heated and then passed through the membranes, and the salt is left behind.
MD is a very efficient way to remove salt from water, and it is also a less energy-intensive process than traditional desalination technologies, such as reverse osmosis. MD is also a more environmentally friendly process, as it does not produce brine, which is a concentrated salt solution that can be harmful to the environment.
Another recent advancement in desalination is the development of forward osmosis (FO) technology. FO is a process that uses a semi-permeable membrane to separate water from contaminants. The membrane allows water molecules to pass through, but not salt molecules. The water is placed on one side of the membrane, and a draw solution is placed on the other side of the membrane. The draw solution is a solution that has a higher concentration of salt than the water. The water molecules move from the water side of the membrane to the draw solution side of the membrane, and the salt is left behind.
FO is a very efficient way to remove salt from water, and it is also a less energy-intensive process than traditional desalination technologies, such as reverse osmosis. FO is also a more environmentally friendly process, as it does not produce brine.
Boron nitride coating is key ingredient in hypersaline desalination technology reported by Rice in Nov 2020
Researchers from the National Science Foundation Engineering Research Center at Rice University have developed a new desalination technology that uses boron nitride coating to increase efficiency. The technology uses a process called membrane distillation, in which hot, salty water is separated from cold, fresh water by a porous membrane.
A photothermal coating heats the brine as it passes over the membrane, and the difference in temperature creates a pressure gradient that drives water vapor through the membrane, leaving behind salts and other contaminants. The boron nitride coating protects the membrane from corrosive hypersaline water, allowing for exponential improvements in water production.
The challenge was to grow this coating on an irregular and porous surface, which is difficult because any defect in the coating could cause corrosion. The researchers used a modified chemical vapor deposition (CVD) technique to grow dozens of layers of hBN on the wire mesh, creating a coating that was only about one 10-millionth of a meter thick. This coating encased the interwoven wires of the mesh and protected them from the corrosive forces of hypersaline water.
To test the effectiveness of the hBN coating, the researchers attached the coated wire mesh heating element to a commercially available polyvinylidene difluoride membrane, which was then rolled into a spiral-wound module commonly used in commercial filters. They then powered the heating element with voltage at a household frequency of 50 hertz and power densities as high as 50 kilowatts per square meter. The system was able to produce a flux of more than 42 kilograms of water per square meter of membrane per hour, which is more than 10 times greater than existing membrane distillation technologies that rely on ambient solar energy. The system also had a higher energy efficiency than existing membrane distillation technologies.
Graphene-based sieve for Seawater desalination
Desalination is another strategy, which is especially effective in coastal areas. But the process had been expensive and energy-intensive. Now, Researchers at the University of Manchester in England have developed a graphene-based membrane that filters the salt out of seawater, making it drinkable. This development could provide drinking water to millions of people who live in countries where access to fresh, drinkable water is limited. It’s also a promising discovery for South Africa – the Western Cape in particular – given the drought.
Graphene oxide membranes have already proven their worth in sieving out small nanoparticles, organic molecules and even large salts. But until now, they couldn’t be used to filter out common salts, which require even smaller sieves. Previous work had shown that graphene oxide membranes became slightly swollen when immersed in water, allowing smaller salts to flow through the pores along with water molecules. Now, Dr Nair and colleagues demonstrated that placing walls made of epoxy resin (a substance used in coatings and glues) on either side of the graphene oxide membrane was sufficient to stop the expansion
These advancements are making desalination a more viable option for providing fresh water to areas that are facing water shortages.
Breakthrough technology purifies water using using metal-organic frameworks (MOFs) & sunlight
A global research team has been able to transform brackish water and seawater into safe, clean drinking water in less than 30 minutes using metal-organic frameworks (MOFs) and sunlight. Lead author Professor Huanting Wang from the Department of Chemical Engineering at Monash University in Australia, said this work opened up a new direction for designing stimuli-responsive materials for energy-efficient and sustainable desalination and water purification. The World Health Organization suggests good quality drinking water should have a total dissolved solid (TDS) of <600 parts per million (ppm). Researchers were able to achieve a TDS of <500 ppm in just 30 minutes and regenerate the MOF for reuse in four minutes under sunlight.
Metal-organic frameworks are a class of compounds consisting of metal ions that form a crystalline material with the largest surface area of any material known. In fact, MOFs are so porous that they can fit the entire surface of a football field in a teaspoon. The research team created a dedicated MOF called PSP-MIL-53. This was synthesised by introducing poly(spiropyran acrylate) (PSP) into the pores of MIL-53 – a specialised MOF well-known for its breathing effects and transitions upon the adsorption of molecules such as water and carbon dioxide. Researchers demonstrated that PSP-MIL-53 was able to yield 139.5L of fresh water per kilogram of MOF per day, with a low energy consumption. This was from desalinating 2,233 ppm water sourced from a river, lake or aquifer.
A research team has developed a new adsorbent-based desalination process that uses metal-organic frameworks (MOFs) and sunlight to purify seawater and brackish water into safe, clean drinking water in less than 30 minutes. The team created a dedicated MOF called PSP-MIL-53 that could yield 139.5L of fresh water per kilogram of MOF per day with low energy consumption. The MOF could be regenerated for reuse in four minutes under sunlight. The research has provided a promising, energy-efficient, and sustainable adsorbent for desalination, which is an exciting new route for the design of functional materials for using solar energy to reduce the energy demand and improve the sustainability of water desalination.
Solar-powered device produces energy and cleans water at the same time
Engineers at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia, have developed a solar-powered device that serves as both a water purifier and an energy generator. The device combines a water distillation system with a solar cell. The solar cell generates electricity while the heat from the solar panel evaporates water in the distiller. The vapor passes through a porous polystyrene membrane that filters out salt and other contaminants, producing clean water.
This innovative technology could be a viable solution to produce drinking water for impoverished communities in developing countries. Researchers estimate that the device could produce about 1.7 kilograms of clean water per hour. However, practical considerations such as deployment and stability in different environments would need to be addressed before the device can be used on a larger scale.
Adoption Of Desalination
Despite these challenges, desalination has the potential to play a critical role in ensuring water security. Countries like Saudi Arabia, Israel, and the United Arab Emirates have already embraced desalination as a key component of their water management strategies. In the United States, California has invested in desalination plants to provide an additional source of water during droughts.
The Sorek Plant in Israel is the largest modern seawater desalination plant in the world and provides 20% of the country’s water. The plant uses reverse osmosis technology, where polymer membranes inside tubes are used to filter seawater and extract fresh water while retaining saltier water. The plant incorporates engineering improvements such as large-diameter pressure tubes, efficient pumps, and energy recovery devices to produce a desalination plant with the lowest energy consumption. Advanced membranes made of atom-thick sheets of carbon hold the promise of further cutting the energy needs of desalination plants in the future.
The United Arab Emirates, Australia, Singapore, and several countries in the Persian Gulf have invested in desalination projects, and California is also starting to embrace the technology. Desalination technology can cost-effectively provide a substantial portion of a nation’s water supply, demonstrating its potential to ensure water security in areas facing water scarcity.
Despite the challenges, desalination has the potential to play a major role in solving the world’s water crisis. It can provide a source of fresh water in areas that are facing water shortages. It can also help to reduce the demand for freshwater from other sources, such as rivers and lakes.
Desalination is not a perfect solution, but it is an important tool that can help to address the world’s water crisis. As the world’s population continues to grow, the water demand will only increase. Desalination will become an increasingly important part of our water management strategy.
As technology continues to advance, the cost of desalination is expected to decrease, making it a more affordable option for many regions around the world. Researchers are exploring new ways to reduce the energy requirements of desalination and develop more sustainable methods of brine disposal.
In conclusion, desalination has the potential to play a crucial role in ensuring water security in regions where traditional water sources are scarce or contaminated. While desalination presents several challenges, including cost and environmental impact, continued technological advancements offer hope for a more sustainable and cost-effective future. As we work to address the global water crisis, desalination should be a key part of the conversation.