Gotland is doing it, Öland is doing the same. Now, municipalities on Sweden's mainland are also investigating the possibility of purifying seawater into drinking water to secure future drinking water supply.
In Borgholm Municipality on Öland, the plan for a desalination plant was born out of a water shortage ten years ago. Inside the facility in Sandvik on the island's northwest side, there is now a pumping station that, via a pipe from the depths of the Baltic Sea, brings in seawater to make it drinkable. Salt, small fish, and seaweed are removed through reverse osmosis - a technique that, through high pressure, purifies saltwater through membranes.
It means that we avoid crisis situations, says Christian Wiström, CEO of Borgholm Energi, to TT.
The plant is used year-round and daily supplies residents in the surrounding area with drinking water.
The drinking water becomes clean, almost too clean, since we afterwards have to add the minerals we get in regular drinking water, says Christian Wiström.
The mainland is following
On southern Gotland, there is the Visby desalination plant. The two islands' method has now inspired several municipalities on the mainland. On the municipality's behalf, Kalmar Vatten is now investigating the conditions for building a desalination plant. Due to poor access to water, Karlskrona will now project a desalination plant that is expected to be in place sometime between 2035 and 2040, says the municipality's water and harbor manager Ola Gren to TT.
Lysekil, in turn, will this year produce a basis for a decision to invest in desalinated seawater. The main reason here is not only low groundwater but also that a long water pipeline needs to be improved, says Sten Kristersson, business strategist at the municipal water company Leva in Lysekil.
Desalting the West Coast can, however, become a larger project with different conditions than on Öland and Gotland, since the water here is saltier, he says.
Cheaper to purify wastewater
But Kenneth M Persson, professor of technical water resources at Lund University, does not believe in desalinated seawater as a future solution for drinking water supply. Instead, he advocates for recirculation - to purify and reuse wastewater as drinking water, without it being released into the environment in between. The method is used in, among other places, Singapore and Namibia, but only in one municipality in Sweden.
Even in this case, Öland is a pioneer: Mörbylånga has a waterworks that makes drinking water from industrial water that the chicken slaughterhouse Guldfågeln has used.
Wastewater has lower salt content, so the pressure required to purify it requires less energy and operating costs than reverse osmosis, Kenneth M Persson means.
It becomes just as clean as desalinated seawater. The resistance is rather emotional, he says.
Then the raw water passes a smaller activated carbon filter to be purified from organic material such as humus, color, etc.
After pre-filtration, the water passes into a pump that presses the water through the membranes. Only the clean water molecule has the ability to pass the filter or membrane.
After filtration, the water is recalcified for better taste.
In 1959, membrane technology, reverse osmosis, was invented, and in the 1970s, desalination of seawater began on a larger scale in many parts of the world with the help of it. In the 2010s, desalination of seawater became a mature technology that could avert several crisis situations with depleted water resources, for example, in Australia.
Membrane technology is used in several countries, including the Middle East and North Africa.
Sources: Royal Institute of Technology (KTH) and forskning.se
