Desalination in the context of global water security

Reverse osmosis desalination plant in Barcelona, Spain. ©James Grellier/Wikipedia Commons

Asit K. Biswas, Cecilia Tortajada and Lauren Greenlee

ONE WATER | March 22, 2024

Desalination is not the only approach that will be required to solve the world’s water scarcity problems. However, it will likely emerge as a central pillar to manage water scarcity. Already today, cities like Barcelona or San Diego would run out of water without desalination plants during periods of drought.

Opportunities are growing for desalination developments

Large funds are being allocated to develop desalination technologies. XPRIZE, for example, has announced an award towards addressing Water Scarcity by developing a seawater desalination technology that would be significantly more economic, robust, and environmentally friendly. The prize is $119 million with the competition running over five years. One of the largest prizes for innovation ever.

Why this focus on desalination?

The Earth’s water challenges are in part influenced by the world’s population growth. Since 1961, the global population has more than doubled, from 3.06 billion to over 8 billion. This population surge, along with a shift towards urbanisation (nearly 60% of people now live in cities compared to a rural majority in 1961), has led to an exponential increase in water requirements.

The demand for water for various human activities, including drinking, sanitation, hygiene, and food production, has grown tremendously, putting immense strain on freshwater resources.A small desalination plant can treat around 100.000m3 per day, which is enough water for a city of several hundred thousand people, a potentially promising endeavour. The energy required for this is roughly equal to ~10.000-20.000 households, assuming an energy demand of 3kWh per m3 desalinated water and 30kWh for households’ daily energy demand.

Desalinating Alternatives

One cost-effective example of a desalination alternative is collecting and properly treating wastewater and then reusing it for all purposes, including drinking. Windhoek, capital of Namibia, has been using treated wastewater for direct potable use for over 50 years. Singapore currently treats all its wastewaters and then reuses it for industrial indirect potable uses.

Furthermore, bolstering management practices can result in tremendous water saving. Cases of success include Japan and Singapore’s overall network of water distribution systems and Cambodia’s notable city Phnom Penh, in which water leakage has been controlled to less than 10% losses. However, in general, globally, losses are high. The degree of water leakage oscillates between 10% and 55%.

In several Gulf nations the per capita daily water use can range from 400 to 600 litres, with leakage rates between 25-30%. If such losses could be reduced to the level of Phnom Penh, there would be notable savings.

The ongoing debate of desalination

Global desalination installed capacities as of 2023 were around 95.37 million  m3/d of water, which is approximately 1% of the world’s drinking water needs. Around 60% of the global desalination capacity is now in Gulf countries. Saudi Arabia is leading in production of desalinated water. The country has the largest covered drinking water storage facility, Briman Strategic Water Reservoir, with a capacity exceeding 2 million m3. It also has the world’s largest mobile desalination plant, with a capacity of 50,000 m3/day. Its Saline Water Conversion Corporation (SWCC) produces 11.5 million m3 of desalinated water per day. Its Ras Al-Khair power and desalination plant is the largest in the world, producing 1,036 million m3/day of desalinated water.

Desalination has considerable potential to alleviate water scarcity in many parts of the world, especially if its costs can be significantly reduced. The world has achieved bringing the cost to less than $0.50/m3 for desalination. Particularly in the Gulf, IDE Technologies accounted for a cost of $0.405/m3 at Soreq 2 as of 2021. In addition, Jubail 3a documented $0.41/m3, Jubail 3b at $0.42/m3, and Yanbu 4 for $0.47 /m3. Unfortunately, these costs are still too high for many parts of the world.

Beyond cost, another major concern with existing desalination practices is their high fossil-fuel-based energy requirements, especially in the current carbon-conscious world. Carbon footprint of desalination plants will be an increasingly important consideration in the future. Carbon footprints depend on many factors, including the source of energy, type of desalination process used, salinity of the source water (brackish or sea) and management practices.

Most desalination plants realistically need 3.5-4.5 KWh of energy to produce a cubic metre of desalinated water. Putting this into perspective, this can be roughly compared to keeping 3-5 household light bulbs (100 watts) on for 10 hours straight in order to produce one metre by metre box of water which then needs to be scaled by millions to serve the global population. As mentioned above, Gulf countries may use 400-600 litres of water a day per person. Now, energy requirements are coming down thanks to technological and management advances. Desalination plants are achieving energy requirements below 3KWh per cubic metre of desalinated water which is in part due to the use of renewable energy and its steadily building momentum.

It is also crucial to account for the brine of the desalination process. Environmental impacts of desalination remain a cause of debate. Brine, a hyper-saline leftover from desalination may pose a threat to marine life. Discharged brine can disrupt ecosystems and harm sensitive organisms near the discharge point if not properly diluted.

Another important aspect in the debate of desalination are sociopolitical factors. Desalination efforts inherently centralise water management and can make securing water resources for communities dependent on large entities be it government, company or other relevant organising body. Desalination technologies and associated impacts can exacerbate existing inequalities and or create new vulnerabilities, including circumstances of transboundary water resources . Therefore, vigilant management of water distribution is essential in order to benefit from mass generation of freshwater. Public trust and acceptance of desalination on the ground is also critical for the success of such enterprises. While many plants can become job opportunities, it can become significant who is selected to work at the plants and how such opportunities are integrated into local society.

History of desalination

The concept of desalinating seawater is not new. Greek polymath Aristotle noted some 2360 years ago: “Salt water, when it turns into vapour, becomes sweet, and the vapour does not form salt water again when it condenses.” However, desalinating seawater was not an option for another two millennia after Aristotle.

Historically, desalination technology has been a global enterprise. The first seawater distillation plant was built in 1869 by the British in Aden (now Yemen) due to the need for freshwater while on route to India. Later on, the first large seawater desalination plant was built on the Caribbean island of Aruba in 1930.

In 1951, Kuwait built its first evaporator-based desalination plant. During the 1950s, the United States became interested in desalination because its Southwest faced a prolonged and severe drought. This resulted in the establishment of the first US Saline Water Conversion Programme in 1952. The Office of Saline Water, created in 1955, was charged with building five desalination demonstration plants in different parts of the country. However, rains returned to the parched region shortly thereafter and the USA’s interest in desalination declined.

To expect:

With the world facing serious water scarcity issues, climate change, urbanisation and population growth are making water availability increasingly more unreliable and complex. As the net cost of desalination comes down steadily, it is highly likely that desalination will play an important role in alleviating the water crisis in many countries in the future.

Asit K. Biswas, Academician and Professor, University of Glasgow; Cecilia Tortajada, Professor, University of Glasgow; Lauren Greenlee, Executive Vice President, XPRIZE Foundation.

This article was published by ONE WATER, March 22, 2024.