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Technically Speaking

by Dave Trecker
e count on the ocean for a lot of things these days– But science marches on and today desalination has at its disposal
shipping, seafood, even deep water mining. And, at the deep-sea robotics from the oil-and-gas industry and advanced
W shoreline, recreation. In Florida we treasure our beaches. terrestrial filters.
But we don’t count on the ocean for fresh water. It’s just too What has people really excited is the notion of putting RO
salty. To get fresh water from the ocean, you would have to remove plants on the ocean floor. That’s right. Submerge the units to depths
some 35 grams per liter of salt, mostly sodium chloride (table salt), where the salt content is lower (less to remove) and the tons of
and there’s no cost-effective way to do it and, up until now, little water pressure from above help force brine through the membranes
incentive to try. (less external energy needed).
But times are changing. The demand for fresh water is soaring. Net savings of up to 40% are projected. And that’s a big deal.
The United Nations says half of the earth’s population experiences There’s an environmental benefit too: The salty brine left behind
a severe water shortage at least once a month and, with the usual is quickly dispersed in the deep ocean without harming aquatic
sources for fresh water drying up, we may have to get what’s needed plants or animals.
from the ocean. There’s now incentive to try harder. As chronicled in the Wall Street Journal, several companies are
That means streamlining desalination – getting rid of those trying to scale up this technology – Flocean (Norway), Waterise
pesky salts more efficiently. (Netherlands) and OceanWell (California).
In Florida, for the moment, we have no shortage of drinking There’s been real progress. Flocean and Waterise have put pilot
water, and fresh water is in short supply in only a handful of places. plants on the ocean floor just offshore of Norway, near North Sea
But that is projected to change in the decades ahead. We, too, will drilling that produces cheap energy for the region. OceanWell is
become dependent on some form of desalination. experimenting in a deep reservoir near Malibu.
Desalination usually takes one of two forms. You can either Flocean has a customer lined up for a small contract and expects
distill the brine and collect the distillate – that is, heat the seawater to have the world’s first deep-sea desalination plant online in late
until it evaporates and convert the steam to pure water on a cold 2026.
surface. Or you can force the brine across a plastic membrane with Then comes the really hard part – seeing if things hang together
holes in it so tiny only the water molecules fit through, leaving over months and years of operation, seeing how much maintenance
behind salt and other impurities. That’s called reverse osmosis (RO). is required, seeing if fluctuations in salinity and temperature affect
The world’s largest desalination plant is in Saudi Arabia and it performance.
uses the energy-intensive distillation process. But the Saudis don’t The odds may be long, but success could ultimately lead to a
sweat the cost. They have plenty of energy in the form of cheap oil. great deal of clean water for millions of people around the globe.
(It’s said that a barrel of fresh water is worth more to the Saudis And that includes Florida.
than a barrel of oil.)
Dr. Trecker is a chemist and retired Pfizer executive living in Naples.
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.

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