Can we produce drinking water without leaving an ecological footprint?

Can we produce drinking water without leaving an ecological footprint?

Bordered by sea on the east and west coasts, Saudi Arabia’s parched landscape is one of the hottest and driest places on Earth. The lines “Water, water everywhere, nor a drop to drink” come to mind when you consider the challenges this arid country faces.

The capital, Riyadh, averages just 6 inches (15 centimeters) a year, while some parts of the country have no rain for the next decade or more. In summer, temperatures in the cities regularly exceed 40C, rising to 55C in the desert. The country has no lakes or rivers and the underground aquifers are quickly depleted.

Needless to say, Saudi Arabia understands the value of water all too well.

But unlike the lost and desperate sailors in Coleridge’s famous poem, “The Rime of the Ancient Mariner,” Saudi scientists have used the salty seawater around them through desalination. Now, as the world’s largest producer of desalinated water, they are building a future where this vital resource is both affordable and sustainable.

Zero carbon desalination

Traditionally, desalination has been achieved through distillation, in which seawater is heated to separate the drinkable liquid from salts and other contaminants. The process is not only energy-intensive, but also expensive.

But this all changed in 2016, when Crown Prince Mohammed bin Salman announced Vision 2030, a strategic plan that aimed to improve life in every part of Saudi society. It included a number of sustainability commitments – such as increasing energy from renewable sources and reducing CO2 emissions – that are now part of the Saudi Green Initiative.

The trickle down effect was seen everywhere, but especially in the country’s water industry. The lead was the Saline Water Conversion Corporation (SWCC), the company that produces about 70 percent of the Kingdom’s desalinated water.

The SWCC launched a program to replace thermal distillation technology in its plants with reverse osmosis, a more energy-efficient process that forces salt water through fine membrane filters. Compared to distillation, according to the SWCC, this method typically uses only a quarter of the energy to produce the same amount of water.

The company has also introduced newer membrane filtration technology — developed by scientists in Saudi Arabia — to cut the amount of energy consumed in half, according to SWCC’s consulting engineer Nikolay Voutchkov. In fact, it’s so effective that in March 2021, the SWCC set a new Guinness World Record for the world’s lowest energy desalination plant for water.

“Despite our achievements so far, we still have the drive to do better,” says Voutchkov.

The SWCC has now set itself targets to halve its energy consumption by 2030 and be carbon neutral by 2050. Much of this change will come from further improving technologies used in the factories, Voutchkov says. These include improved membrane filtration systems, new energy recovery equipment that will reduce waste to virtually zero and more energy efficient pumps, all of which will help reduce fossil fuel use.

The SWCC also plans to introduce more advanced carbon capture and storage processes into its distillation processes and implement an extensive tree planting program at its sites to encourage further CO storage.2 emissions.

Their desalination plants are also being made smarter. Using AI systems, machines can autonomously maximize their energy and chemical use while producing water, says Voutchkov.

Perhaps some of those carbon emissions could also be saved by harnessing the power of the sun — something scientists at the King Abdullah University of Science and Technology (Kaust) in Saudi Arabia have been investigating.

A futuristic proposal under consideration is a “solar dome,” which will concentrate the sun’s heat to evaporate seawater and produce freshwater. Similar types of technology are already being used to produce electricity through steam power, but if scientists find it viable for large-scale application, it will be the first time it is used for desalination.

Researcher working at the Desalination Technology Research Institute (DTRI)

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Researcher working at the Desalination Technology Research Institute (DTRI)

(SWCC)

But more realistic prototypes have already been built in Kaust. In one, desalination equipment was combined with solar panels, so the heat generated by these panels can help evaporate seawater. Tests have shown that it can produce as much as 1.64 l of water per square meter of solar panel surface every hour and that water needs no further treatment to be used for agriculture.

Turning brine into a resource

Desalination – even of the energy-efficient reverse osmosis variant – presents another challenge: brine. This by-product has the potential to affect coastal life and ecology, as some desalination plants simply dump it back into the sea. As a country without lakes or rivers, Saudi Arabia is indeed the world’s largest producer of brine.

Again, Voutchkov has an ambitious plan: to turn the by-product into a resource. “The desalination industry is often challenged about the impact of brine discharges on the marine environment,” he explains. “However, the reality is that today the desalination industry and regulators have a comprehensive system in place to predict, monitor and control potential environmental impacts during all phases of project development and implementation.”

In Saudi Arabia, discharges from desalination plants are continuously monitored to ensure that the marine environment is preserved and protected, and all waste is treated to an environmentally sound standard, Voutchkov said.

He adds that brine is rich in minerals, including sodium chloride, magnesium and rubidium, and that extracting these valuable resources could support an entirely new industrial chain.

“The commercial returns have the potential to fully subsidize the cost of water production in Saudi Arabia, as well as lead us to new sources of renewable energy for the Kingdom,” he says.

There are already plans to build a new treatment plant in the Kingdom that will act as a “brine mine” where minerals and rare metals will be removed from the brine. Sodium chloride is then sold, for example, to local chlor-alkali companies that produce products such as chlorine and caustic soda.

According to Dr Ahmad Al Amoudi, director of the Institute for Research, Innovation and Desalination Technologies at SWCC, arrangements have already been made with several chlor-alkali producing companies in Saudi Arabia to supply these raw materials once the plant is operational.

The team of dr. Al Amoudi is also working with the US Department of Energy on a joint research program to look at ways to extract rubidium from brine to produce environmentally friendly energy.

Hydrogel technology

In the misty deserts of Namibia, where rain is rare and fauna is thirsty, ingenuity is rewarded. This is why the mist-giant beetle, a creature no bigger than a strawberry, can be seen climbing high sand dunes and performing handstands. At these watery heights, the mist condenses on the beetle’s body and rolls right into its mouth, completing the successful, seemingly magical extraction of water from the air.

At Kaust, researchers are perfecting a technology that produces similarly ingenious results. In 2018, Peng Wang and his team at the university’s Water Desalination and Reuse Center created a hydrogel — a polymer that resembles a black, squishy blob — that can capture water from the air for other uses or even drinking.

Hydrogel can literally pull water out of thin air

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Hydrogel can literally take water out of the air

(Getty)

The hydrogel contains calcium chloride, a non-toxic salt that is especially thirsty; it absorbs water vapor and moisture from the air and then releases the liquid when exposed to the right conditions.

In Kaust’s prototype tests, 35 g of hydrogel captured 37 g of water; after being out in the sun for a few hours, the pure water separated from the gel and was collected. The lab estimated that collecting 3 liters of water could cost as little as half a cent a day, a particularly important factor for the less wealthy regions of the country in the coming years.

The next stage was to move water production from a batch process to a continuous process – a task the team accomplished in 2019. And in 2020, the team was able to develop a prototype solar panel that was cooled with water from the hydrogel, an innovation especially useful in the heat of the Middle East.

It is a little known fact that as temperatures rise, solar panels actually produce less energy and become more inefficient. In tests, Kaust researchers found that the water released by the hydrogel can cool the solar panels by as much as 10C, dramatically improving their efficiency.

Renyuan Li, the principal investigator of the project, said in announcing the research results: “We believe that this cooling technology can meet the demands of many applications because water vapor is everywhere and this cooling technology can be easily adapted to different scales.

“The technology can be made as small as a few millimeters for electronic devices, hundreds of square meters for a building or even larger for passive cooling of power plants.”

The future of water

As the effects of climate change increase, resources like water will only become more valuable, meaning it’s more important than ever to produce it cheaply and sustainably. And the research and innovations already taking place in Saudi Arabia could provide a model that could be replicated in other parts of the world where water is scarce.

Like dr. Al Amoudi says, “Water is so important to life and we need to protect it for future generations.”

The Saudi Green Initiative is Saudi Arabia’s government-wide approach to combating climate change.

[The article was originally published in October 2021]

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