Into the Briny Deep

By Dave Trecker

We count on the ocean for a lot of things these days–shipping, seafood, even deep water mining. And, at the shoreline, recreation. In Florida we treasure our beaches.

But we don’t count on the ocean for fresh water. It’s just too salty. To get fresh water from the ocean, you would have to remove some 35 grams per liter of salt, mostly sodium chloride (table salt), and there’s no cost-effective way to do it and, up until now, little incentive to try.

But times are changing. The demand for fresh water is soaring. The United Nations says half of the earth’s population experiences a severe water shortage at least once a month and, with the usual sources for fresh water drying up, we may have to get what’s needed from the ocean. There’s now incentive to try harder.

That means streamlining desalination – getting rid of those pesky salts more efficiently.

In Florida, for the moment, we have no shortage of drinking water, and fresh water is in short supply in only a handful of places. But that is projected to change in the decades ahead. We, too, will become dependent on some form of desalination.

Desalination usually takes one of two forms. You can either distill the brine and collect the distillate – that is, heat the seawater until it evaporates and convert the steam to pure water on a cold surface. Or you can force the brine across a plastic membrane with holes in it so tiny only the water molecules fit through, leaving behind salt and other impurities. That’s called reverse osmosis (RO).

The world’s largest desalination plant is in Saudi Arabia and it uses the energy-intensive distillation process. But the Saudis don’t sweat the cost. They have plenty of energy in the form of cheap oil. (It’s said that a barrel of fresh water is worth more to the Saudis than a barrel of oil.)

Almost everywhere else the cost of energy is a factor, and that means using reverse osmosis. But RO isn’t cheap either and it’s used mostly in small operations inland that produce fresh water at costs of $4-6 per 1,000 gallons. Large seawater RO plants located at the shoreline are few and far between. The pressure needed to force the water across the membrane costs a bundle and even big utilities have not been able to bear the expense.

But science marches on and today desalination has at its disposal deep-sea robotics from the oil-and-gas industry and advanced terrestrial filters.

What has people really excited is the notion of putting RO plants on the ocean floor. That’s right. Submerge the units to depths where the salt content is lower (less to remove) and the tons of water pressure from above help force brine through the membranes (less external energy needed).

Net savings of up to 40% are projected.

And that’s a big deal.

There’s an environmental benefit too: The salty brine left behind is quickly dispersed in the deep ocean without harming aquatic plants or animals.

As chronicled in the Wall Street Journal, several companies are trying to scale up this technology – Flocean (Norway), Waterise (Netherlands) and Ocean Well (California).

There’s been real progress. Flocean and Waterise have put pilot plants on the ocean floor just offshore of Norway, near North Sea drilling that produces cheap energy for the region. Ocean Well is experimenting in a deep reservoir near Malibu.

Flocean has a customer lined up for a small contract and expects to have the world’s first deep-sea desalination plant online in late 2026.

Then comes the really hard part – seeing if things hang together over months and years of operation, seeing how much maintenance is required, seeing if fluctuations in salinity and temperature affect performance.

The odds may be long, but success could ultimately lead to a great deal of clean water for millions of people around the globe. And that includes Florida.

Dr. Trecker is a chemist and retired Pfizer executive living in Naples.