Desalination: What is it and how can it help tackle water scarcity? As the World Economic Forum’s 2024 Global Risks Report warns that a natural resources crisis is one of the leading global long-term threats, ways to tackle the water crisis are the need of the hour. Read here to learn more.
Billions of people turn on a tap and expect clean drinking water to flow out, but this is not true for billions of others.
Rapid population growth, urbanization and increased global water consumption by agriculture, industry and energy have left many countries facing the threat of water scarcity.
One solution to meet the growing demand for freshwater is desalination, which involves removing the salt from seawater to produce drinking water.
While this process alone can’t prevent a global water crisis, it can play a vital role in providing more people worldwide with access to clean, safe drinking water.
Water crisis of the future
Water scarcity occurs when water demand outstrips available supply during a specific period when water infrastructure is inadequate or institutions fail to balance people’s needs.
- In 2022, 2.2 billion people lacked safely managed drinking water, including more than 700 million people living without a basic water service, according to the United Nations.
- By 2030, there could be a 40% global shortfall in freshwater resources, which combined with world population growth that’s set to increase from 8 billion today to 9.7 billion by 2050, would leave the world facing an extreme water crisis.
- Sub-Saharan Africa is expected to see the biggest change in water demand, with a projected 163% increase by mid-century, World Resources Institute data shows. This is four times the expected rate of change in Latin America, the second-highest region.
- Almost two-thirds of the planet’s surface is covered with water, and our oceans hold 96.5% of all water on Earth.
- However, its salt content makes this water unsuitable for humans to drink. This is where desalination comes in.
What is Desalination?
Desalination is the process of removing salt and other minerals from saline water (seawater or brackish water) to produce fresh water that is suitable for human consumption, agriculture, and industrial uses.
The primary goal of desalination is to make saltwater, which is abundant on Earth, usable for purposes that require fresh water, which is comparatively scarce.
- In most desalination processes, for every litre of potable water produced, about 1.5 litres of liquid polluted with chlorine and copper are created.
- This wastewater (“concentrate”) is twice as saline as ocean water. If not properly diluted and dispersed, it may form a dense plume of toxic brine which can degrade coastal and marine ecosystems unless treated.
- Increased salinity and temperature can cause a decrease in the dissolved oxygen content and contribute to the formation of “dead zones”, where very few marine animals can live.
- Unconventional water resources, such as those resulting from desalination, are key to supporting Sustainable Development Goal 6 (to ensure the availability and sustainable management of water and sanitation for all).
- Seawater desalination can extend water supplies beyond what is available from the hydrological cycle, but innovation in brine management and disposal is required.
- Research suggests there are also economic opportunities associated with brine, such as commercial salt, metal recovery and the use of brine in fish production systems.
- The last decade has seen increased academic interest in recovering resources from brine, according to one study. Seawater contains various minerals, some of which are rare and expensive to mine on land. While extracting materials from brine is possible, its high cost restricts commercialization.
Key Desalination Technologies
- Reverse Osmosis (RO): This is the most common and energy-efficient method. It involves forcing saltwater through a semi-permeable membrane that blocks salts and other impurities, allowing only water to pass through. RO is widely used due to its effectiveness in removing salts and other chemical contaminants.
- Thermal Desalination: This category includes methods like Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED). These processes involve heating seawater to create steam, which is then condensed to produce fresh water, leaving salts and other impurities behind.
- Electrodialysis (ED): This method uses a series of membranes and an electrical current to separate positive and negative ions, including salt, from water. It is particularly effective for treating brackish water.
Desalination can Help Tackle Water Scarcity
- Supplementing Freshwater Supplies: In regions where freshwater resources are scarce, desalination provides a consistent and reliable source of water that is independent of climate variability.
- Supporting Growing Populations: As populations increase, especially in arid regions or small island nations, desalination offers a way to support the growing demand for drinking water and sanitation needs.
- Agricultural Use: Desalinated water can be used for irrigation in areas where freshwater is too precious to be used for agriculture, thus helping in food production and the alleviation of food scarcity.
- Industrial Applications: Many industries require high-quality, consistent water supply. Desalination can provide this, especially in areas where industrial growth is limited by water scarcity.
Challenges
- High Costs: Desalination is energy-intensive and can be expensive, both in terms of initial capital outlay and operational costs. This makes it less accessible for poorer regions without the necessary financial resources.
- Environmental Impact: The desalination process produces brine (highly concentrated salt water), which must be carefully managed to avoid damaging marine ecosystems. Additionally, the energy consumption required for desalination can contribute to greenhouse gas emissions unless renewable energy sources are used.
- Energy Requirements: The process is traditionally reliant on large amounts of electricity and/or thermal energy, making it not only costly but also a significant contributor to carbon emissions unless powered by renewable energy sources.
Innovations for clean drinking water
Several innovative desalination systems are being developed to try and reduce the energy required to operate them and related emissions.
Wave-powered desalination
- Oneka, a wave-powered desalination technology, is one such innovation. Floating buoys tethered to the ocean floor use wave power to drive a pump that forces seawater through filters and reverse osmosis membranes.
- The fresh water is then piped ashore again powered solely by the natural motion of waves, explains Canadian desalination company Oneka Technologies.
- The system has several advantages over large-scale shore-based desalination plants that are mostly powered by combusting fossil fuels, but it does require high waves to work.
Solar-low-cost water purification
- Solar power has been used to convert saltwater into fresh drinking water, by researchers from King’s College in London in collaboration with MIT and the Helmholtz Institute of Renewable Energy Systems.
- A set of specialized membranes channel salt ions into a stream of brine, leaving fresh drinkable water. The system adjusts to variable sunlight without compromising the volume of drinking water produced.
- The process is 20% cheaper than traditional desalination methods, which could boost efforts to provide drinking water in developing countries, the researchers say.
Why in the news?
In a few years, Chennai is set to emerge as the desalination capital of India, with three operational plants in Minjur and Nemmeli and Southeast Asia’s largest plant, with a capacity to treat 400 million litres of seawater a day, coming up at Perur.
- Experts suggest a multi-pronged approach towards water resilience, along with desalination.
Way Forward
A natural resources crisis like water scarcity is listed in the World Economic Forum’s Global Risks Report 2024, as one of the top 10 threats facing the world in the next decade.
To make desalination a more viable option for addressing global water scarcity, advances in technology are focusing on reducing energy consumption and mitigating environmental impacts.
Innovations include the development of more efficient membranes for reverse osmosis, the use of renewable energy sources like solar or wind to power plants, and improved brine management techniques to lessen ecological footprints.
As these technologies improve and become more cost-effective, desalination is likely to play an increasingly important role in global water management strategies, especially in regions severely affected by water scarcity.
Related articles:
-Article by Swathi Satish
Leave a Reply