Seawater desalination plants have gained prominence in recent days as a result of the restrictions to deal with the critical moment that Catalonia is suffering due to the drought. The fact is that this is not a new concept, they have been manufactured for decades, but in the face of uncertainty due to the lack of water, they are now presented as an alternative and an emergency solution to alleviate the water crisis . Companies that market them consulted by acknowledge that in recent months they have received numerous inquiries from Catalonia from different sectors, such as those linked to tourism, especially from hotels on the Costa Brava and from campsites in coastal areas to fill swimming pools, although also from some councils for oral consumption, and from other areas, from farmers for regfins to yacht clubs or boat owners to clean boats.
The producers of these plants are waiting for orders to be finalised, and emphasize that they take care of the manufacture, transfer and commissioning, but remember that it is the customer who has to manage the confusing and slow permits with the Administration to capture the water.
In the case of Catalonia, a modification of the special drought plan will allow the installation of privately owned seawater desalination plants and will be studied case by case, with the condition that this measure serves to guarantee economic activity and places of work The trigger for this change was the proposal launched by the hoteliers of Lloret de Mar to acquire a desalination plant, an issue that has already reached the Catalan Water Agency, which “reviews the feasibility, the reports and the authorizations necessary” from different “involved technical units and legal services”.
Roses City Council, with the impetus of the local tourism sector, has also shown interest in having an infrastructure of this kind, as have the Maresme hoteliers. Some promoters even propose that the surplus water can be diverted to the river course to regenerate aquifers, resold to other individuals to fill swimming pools or be connected to the public network.
But how do these plants work? Compared to the large infrastructures of public desalination plants, such as the current ones in Prat de Llobregat and la Tordera, the so-called private, portable or prefabricated ones stand out for their quick installation and can be transported in a truck in a container to the destination. The ones that create the most interest are, above all, those of a small and medium size, with a capacity from 10 m3 per day – they could supply around a hundred people – up to 500 m3 per day or 1,000 m3 – with a production for to around 5,000 people and 10,000 people, respectively – although there are larger ones, up to 5,000 m3 per day, for a population of approximately 50,000 people.
Depending on the production, the prices vary. As a guideline, they range from 7,000 euros for the most modest ones to half a million or a million euros for the average ones and higher prices for those with the highest capacity. According to sources consulted, depending on the size and design, these modules can be manufactured in about six weeks in the case of the smallest plants, and five, six or eight months for medium or larger plants. There are also companies dedicated to renting them.
According to data from the Spanish Association of Desalination and Reuse (AEDiR), in Spain around five million cubic meters are produced per day of desalinated sea or brackish water for supply, irrigation and industrial use through the most of 700 plants of these characteristics throughout the territory with productions exceeding 100 m3 per day.
“Desalination seems to be fashionable, but the first desalination plant in Spain dates back to 1964, in the Canary Islands. Since then, the technology of desalination plants has been researched, innovated and optimized a lot, especially in terms of sustainability and cost”, highlights M. Carmen García Panadero, general director of Seta Pht and vice-president of AEDiR.
Technically, these plants desalinate the water through reverse osmosis. “It’s a process in which a semi-impermeable membrane is used and a certain pressure is needed to set aside the salts and make the sea water potable”, explains Raquel Hernando, head of water treatment engineering at the Corsa group. For the installation, some “minimum civil work requirements” are needed with a run-of-the-mill slab or concrete blocks. Then it is necessary to connect the inlet of water collected through a pipe or a pump, the outlet of the filtrate and concentrate, as well as the electrical outlet. And they start working. “It is the so-called plug and play system. Practically, it’s arriving, connecting the plant and testing that everything works well”, comments Jose García, Business Development Manager of ImWater Treatment Plants.
On the other hand, the development of new technologies has made it possible to make them more energy efficient with the use of energy recuperators, more efficient reverse osmosis membranes or the use of renewable energy with solar panels. In this sense, sources in the sector point out that the main expense of desalination is the high energy consumption, something that represents around 60% of the cubic meter of desalinated water. “A couple of decades ago we consumed 20 kilowatt hours per cubic meter and currently we are below three kilowatt hours per cubic meter”, explains Panadero.
Permits are required for collection and emission, that is, what is returned to the sea, such as brine. And for portable desalination plants of less than 3,000 m3 per day, there is no need to make environmental impact statements, according to Royal Decree 1/2008.
