Desalination debate: Is the ocean viable to fight water scarcity?

WASHINGTON: While around 70% of Earth’s surface is covered with water, less than 1% percent is actually drinkable.

These finite freshwater resources are very unevenly distributed. In hot, dry regions with growing populations and increasing living standards, there is not enough water to go around — a situation exacerbated by climate change. 

As solutions such as cloud seeding or even iceberg harvesting remain unproven at scale, the desalination of our oceans into drinking water has emerged as the ultimate means to drought-proof regions suffering water poverty.

The centuries-old concept uses thermal distillation or a reverse osmosis membrane to separate salt from the sea.

The technique is now being utilized globally, with well over 20,000 desalination plants currently operating in over 170 countries — the 10 largest in Saudi Arabia, the United Arab Emirates (UAE) and Israel. Around 47% of the world’s desalinated water is produced in the Middle East and North Africa alone, Manzoor Qadir, deputy director of the United Nations University Institute for Water, Environment and Health, told DW.

These arid regions have few other options since, according to Qadir, they generate less than 500 cubic meters of water per capita through rainfall or river runoff — which is half the upper limit of water scarcity as defined by the UN.

The United States, by contrast, produces 1,207 cubic meters of freshwater per person.  Water poverty is set to worsen as populations increase along with temperatures, with Sub-Saharan Africa predicted to become a “hotspot of water scarcity” by 2050, Qadir noted.

“It is a great option in terms of enhancing water resources,” he said of desalination, adding that costs have “decreased tremendously” — from around $5 ($4.69) per cubic meter (1,000 liters) in the 2000s to 50 cents today.

“It’s a no brainer,” said Frithjof C. Kuepper, chair in marine biodiversity at the University of Aberdeen and an expert on the environmental impacts of desalination in Cyprus. “For countries like Cyprus, there’s no other option if they want to maintain this living standard.” The hottest and driest nation in the EU, Cyprus relies on desalination for 80% of its drinking water, according to Kuepper. 

With variable rainfall necessitating water restrictions in the country as far back as the 1990s, Kuepper explains that Cyprus’ government first tried to make up the shortfall by shipping in water from Greece.

“But it cost about ten times more than desalinating,” he said, adding that the government started to build desalination plants in the early 2000s to avoid water shortages.

But both Kuepper and Qadir concede that before becoming a magic bullet for water scarcity, desalination presents some serious environmental trade-offs in its current guise. Firstly, separating salt from water is highly energy intensive. 

A 2021 study on the environmental consequences of removing salt from seawater in Cyprus co-authored by Kuepper showed that the four desalination plants in the country generate around 2% of its total greenhouse gas emissions.

The plants also accounted for 5% of the total electricity consumption in Cyprus, representing one of the largest shares by sector of electricity consumption, according to the study.

Furthermore, the report notes that desalinated water produced around 103 million cubic meters of toxic, high-salinity brine effluent that impacted the Mediterranean seagrass ecosystem in the region of the discharge pipes.

In a report co-authored by Manzoor Qadir on the state of desalination and brine production globally, it was shown that increased salinity, combined with climate-driven temperature rise, can cause a decrease in the dissolved oxygen content, resulting in conditions called hypoxia.