CARLSBAD, Calif. — About four miles off the Southern California coast, a company bets it can solve one of desalination's biggest problems by moving the technology deep below the ocean's surface.
OceanWell's planned Water Farm 1 would use natural ocean pressure to power reverse osmosis — a process that forces seawater through membranes to filter out salt and impurities — and produce up to 60 million gallons of freshwater daily.
Jaden Gilliam, OceanWell project engineer, left, and Mark Golay, director of engineering projects, lower a prototype reverse osmosis pod Dec. 1 into Las Virgenes Reservoir in Westlake Village, Calif.
Desalination is energy intensive, with plants worldwide producing between 500 and 850 million tons of carbon emissions annually — approaching the approximately 880 million tons emitted by the entire global aviation industry.
OceanWell claims its deep sea approach — 1,300 feet below the water's surface — would cut energy use by about 40% compared to conventional plants while also tackling the other major environmental problems plaguing traditional desalination: the highly concentrated brine discharged back into the ocean, where it can harm seafloor habitats, including coral reefs, and the intake systems that trap and kill fish larvae, plankton and other organisms at the base of the marine food web.
"The freshwater future of the world is going to come from the ocean," CEO Robert Bergstrom said. "And we're not going to ask the ocean to pay for it."
As climate change intensifies droughts, disrupts rainfall patterns and fuels wildfires, more regions turn to the sea for drinking water. More than 20,000 plants now operate worldwide, and the industry expanded about 7% annually since 2010.
However, scientists warn that as desalination scales, damage to coastal ecosystems — many already under pressure from warming waters and pollution — could intensify.
A prototype OceanWell reverse osmosis pod is lowered Dec. 1 into Las Virgenes Reservoir in Westlake Village, Calif., where the desalination technology is tested.
Search for solutions
Some companies power plants with renewable energy, while others are developing more efficient membrane technology to reduce energy consumption. Still others are moving the technology underwater entirely.
Norway-based Flocean and Netherlands-based Waterise tested subsea desalination systems and are working toward commercial deployment.
OceanWell signed an agreement to test its system in Nice, France — another region facing intensifying droughts and wildfires — this year.
For now, its technology remains in development. A single prototype operates in the Las Virgenes Reservoir, where the local water district partnered with the company to diversify its water supply. If successful, the reverse osmosis pods eventually would float above the sea floor in the Santa Monica Bay, anchored with a minimal concrete footprint, while an underwater pipeline would transport freshwater to shore.
The system would use screens designed to keep out even microscopic plankton and would produce less concentrated brine discharge.
Gregory Pierce, director of UCLA's Water Resources Group, said deep sea desalination appears promising from an environmental and technical standpoint, but the real test will be cost. "It's almost always much higher than you project" with new technologies, he said.
Las Virgenes Reservoir serves about 70,000 residents in western Los Angeles County. Nearly all the water originates in the northern Sierra Nevada and is pumped about 400 miles over the Tehachapi Mountains — a journey that requires massive amounts of energy. During years of low rainfall and snowpack in the Sierra, the reservoir and communities it serves suffer.
A desalination plant's intake lagoon is seen Dec. 2 on the right, and the discharge canal on the left, in Carlsbad, Calif.
California's desalination dilemma
About 100 miles down the coast, the Carlsbad Desalination Plant became a focal point in a debate over desalination's environmental tradeoffs.
The plant came online in 2015 as the largest seawater desalination facility in North America. Capable of producing up to 54 million gallons of drinking water daily, it supplies about 10% of San Diego County's water — enough for about 400,000 households.
In Southern California, intensifying droughts and wildfires exposed the region's precarious water supply. Agricultural expansion and population growth depleted local groundwater reserves, leaving cities dependent on imported water. San Diego imports about 90% of its supply from the Colorado River and Northern California — sources increasingly strained by climate change.
Desalination was pitched as a solution: a local, drought-proof source of drinking water drawn from the Pacific Ocean. However, many experts say water recycling and conservation should come first.
Garibaldi, California’s state fish, which are vulnerable to impingement on desalination intake screens, swim Dec. 2 in La Jolla, Calif.
Environmental groups argued the Carlsbad plant's seawater intake and brine discharge pose risks to marine life, while its high energy demands drive up water bills and worsen climate change. About 95% of coastal wetlands were lost in California largely to development, leaving remaining lagoons as vital habitats for fish and migratory birds.
Before the plant came online, environmental organizations filed more than a dozen legal challenges and regulatory disputes. Some resulted in changes to the project's design and permits.
"It sucks in a tremendous amount of water, and with that, sea life," said Patrick McDonough, a senior attorney with San Diego Coastkeeper, which participated in legal challenges to the project. "We're not just talking fish, turtles, birds, but larvae and spores — entire ecosystems."
A 2009 Regional Water Quality Control Board order estimated the plant would entrap about 10 pounds of fish daily and required offsetting those impacts by restoring wetlands elsewhere. Seventeen years later, that restoration remains incomplete.
Reverse osmosis machinery operates Dec. 2 at the desalination plant in Carlsbad, Calif.
Michelle Peters, chief executive officer of Channelside Water Resources, which owns the plant, said the facility uses large organism exclusion devices and one-millimeter screens to minimize marine life uptake, though she acknowledged some smaller species can still pass through.
The plant dilutes its brine discharge with additional seawater before releasing it back into the ocean, she said. A 2019 study found the plant's brine discharge raises offshore salinity above permitted levels, though it detected no significant biological changes.
Peters said the plant also cut its energy consumption and operates under a plan aimed at making the facility carbon net-neutral.
Climate change is fueling a desalination boom
A prototype OceanWell reverse osmosis pod sits on the dock Dec. 1 at the Las Virgenes Reservoir in Westlake Village, Calif., where the technology is tested.
Jaden Gilliam, OceanWell project engineer, left, and Mark Golay, director of engineering projects, lower a prototype reverse osmosis pod Dec. 1 into the reservoir.
The intake screen of OceanWell's prototype reverse osmosis pod, designed to allow microscopic organisms such as plankton to safely pass through, is seen Dec. 1 in Westlake Village, Calif.
A prototype OceanWell reverse osmosis pod is lowered Dec. 1 into Las Virgenes Reservoir in Westlake Village, Calif.
The Carlsbad desalination plant's intake lagoon is seen Dec. 2 on the right and the discharge canal on the left.
A sectioned-off area of the Agua Hedionda Lagoon marks the seawater intake for the Carlsbad desalination plant Dec. 2 in Carlsbad, Calif.
Reverse osmosis machinery operates Dec. 2 at the Carlsbad desalination plant in Carlsbad, Calif.
Pipes carrying brackish feed water Dec. 2 run through the Carlsbad desalination plant.
Pipes carrying brine and other substances Dec. 2 run through the Carlsbad desalination plant.
Remnants of fire-damaged homes are seen Dec. 1 in the Palisades neighborhood of Los Angeles, Calif.
Garibaldi, California’s state fish, which are vulnerable to impingement on desalination intake screens, swim Dec. 2 in La Jolla, Calif.
A sea lion basks in the sun Dec. 3 in La Jolla, Calif.
Kelp rises Dec. 2 from a thinned kelp forest in La Jolla, Calif.
