Barcelona bets on water desalination to mitigate drought

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Desalination of water in Barcelona takes place, among other things. At the Llobregat plant, which, after launching in 2009. was virtually unused. It has been working at maximum capacity since late last summer to mitigate the effects of Spain’s prolonged drought. Water shortages are particularly acute in northeastern Catalonia, where water resources are projected to decrease by 18% by 2050. While desalination in Barcelona accounted for 2021. only 3% of consumption (63% came from surface water and 34% from groundwater), now it’s 33%, compared to 19% from rivers. The Llobregat desalination station can produce 200 million liters of potable water per day, or 60 hm³ per year. For drought-stricken Catalonia, this is an ad hoc solution because it comes with consequences.

Desalination a key part of Spain’s water policy

The Mediterranean is heating up faster than many other areas in the world, leading to a record hot year in 2022 and widespread drought in Spain. Until two years ago, Barcelona’s rivers supplied 63% of its drinking water, wells 34%, and desalination only 3%. According to the Barcelona Municipal Water Company, in 2023. Desalination provides1/3 of drinking water, wells less than1/4, and shrinking rivers less than 1/5.

Desalination has been a key part of Spain’s water policy for more than half a century. This country has about 800 desalination plants capable of producing 5 million liters of drinking water per day. According to the Spanish Desalination and Water Reuse Association, Spain currently ranks fourth in the world in terms of desalination capacity and provides 5% of global production.

Catalonia has water restrictions that affect agriculture, industry and some municipal uses, such as an allocation of 230 liters per person per day. Last year, the head of Catalonia’s Water Agency warned that the Barcelona area could face a “drought emergency,” which will be reached when reserves fall below 16% (with reservoirs fed by Catalonia’s northern river basins only 25% full). As part of its drought response package (worth €2.2 billion), the Spanish government has pledged €220 million to expand another desalination station north of Barcelona and €224 million to improve water treatment systems in southern Spain.

Water desalination – how does the Llobregat plant in Barcelona work?

The Llobregat desalination plant is an installation designed to convert seawater into fresh water to increase the availability of drinking water in the Barcelona metropolitan area. It serves 4.5 million residents and can provide up to 24% of the water used in the metropolitan area.

Desalination involves taking water from a distance of 2.2 km from the shore and from a depth of about 30 m – the desalination plant first purifies it and removes turbidity, microbiology and algae. The actual process takes place when water at a pressure of 70 atmospheres is directed to membranes, impermeable to salt or the elements it contains. After this process, fresh water is now available, but it is not drinkable. This is followed by its remineralization and final disinfection. Of every 100 liters of seawater, 45 will be converted into drinking water and 55 will be returned to the sea. The brine produced is sent to the balancing tower of the underwater mouth of the Baix Llobregat treatment plant and mixed with treated water effluent, which it discharges into the sea 3 km off the coast, at a depth of 60 meters.

Desalination of water and the controversy surrounding the technique

The desalination process at the Llobregat plant produces about 0.55 liters of very salty brine as waste for every 0.45 liters of fresh water. The reverse osmosis process, which separates salt from water, requires a large amount of energy, which does not yet come entirely from renewable sources.

Carlos Miguel, plant manager, explained that desalination is more costly than in conventional river or reservoir water treatment plants. “We knew that sooner or later a drought would come,” he added. – “As long as it lasts, the plant will operate.”

According to the public company that runs the Llobregat plant, it costs €0.70 to produce one thousand liters of desalinated water, compared to €0.20 for the same amount of water taken from the Llobregat River and treated for drinking. This means a higher tax burden and possibly higher water bills.

Xavier Sánchez-Vila, a professor of civil engineering and an expert on civil engineering. of groundwater at the Universitat Politecnica de Catalunya, said desalination plants such as Llobregat in Barcelona have provided a lifeline to Catalonia’s residents in times of crisis, but authorities should continue to diversify their strategies and focus on improving ways to treat and reuse water. “We know that with climate change, droughts will become more frequent and therefore there is a need for desalination. But from an economic standpoint, I’m not entirely sure it makes sense to continue building desalination plants. It’s a really expensive solution,” Sánchez-Vila explained.

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