BY HAYLEY SMITH STAFF WRITER
SEPT. 19, 2023 UPDATED 6:57 AM PT
A water district best known for supplying the celebrity-studded enclaves of Calabasas and Hidden Hills could soon become famous for a very different reason.
The Las Virgenes Municipal Water District recently partnered with California-based OceanWell to study the feasibility of harvesting drinking water from desalination pods placed on the ocean floor, several miles off the coast of California.
The pilot project, which will begin in Las Virgenes’ reservoir near Westlake Village, hopes to establish the nation’s first-ever “blue water farm.”
THE COMPANY SAYS THAT BY COMBINING DESALINATION WITH OFF-SHORE ENERGY TECHNOLOGY, IT CAN SOLVE MANY OF THE CHALLENGES ASSOCIATED WITH TRADITIONAL, LAND-BASED DESALINATION, INCLUDING HIGH ENERGY COSTS AND SALTY BYPRODUCTS THAT THREATEN MARINE LIFE. THE PROCESS COULD PRODUCE AS MUCH AS 10 MILLION GALLONS OF FRESH WATER PER DAY — A SIGNIFICANT GAIN FOR AN INLAND DISTRICT ALMOST ENTIRELY RELIANT ON IMPORTED SUPPLIES.
“IT GIVES US A SENSE OF LONG-TERM WATER RELIABILITY, BUT IT ALSO GIVES US THE IDEA THAT WE CAN REALLY START WEATHERING THE STORMS, IF YOU WILL, WHEN IT COMES TO CLIMATE CHANGE IMPACTS, AND SPECIFICALLY DROUGHTS,” SAID MIKE MCNUTT, A SPOKESMAN FOR LAS VIRGENES. “THIS CAN BE A GAME CHANGER FOR LAS VIRGENES, BUT IT COULD BE A GAME CHANGER FOR ANY WATER AGENCY ANYWHERE.”
LOCAL ENVIRONMENTAL GROUPS SAID THE CONCEPT SEEMS PROMISING, BUT NOT WITHOUT DOWNSIDES.
“Our policy is that ocean desalination should always be the last resort,” said Charming Evelyn, chair of the Sierra Club’s water committee in Southern California. “Water is not an infinite resource. It is extremely finite, and the ocean is not something we just get to dip a large straw in and pull whatever we want out, because even the ocean has to maintain a balance.”
The traditional desalination process pumps seawater from coastal areas into facilities on land, where the water is pushed through fine membranes and filters to remove salt and other materials. The process is energy intensive — often fueled by greenhouse-gas-emitting fossil fuels — and produces a thick, briny sludge on the back-end that is typically released back into the ocean. Studies have shown the concentrated brine can be harmful to marine life.
But OceanWell says its technology can use up to 40% less energy by harvesting the water in pods placed at depths of about 1,400 feet, where naturally immense water pressure can help power the filtration process.
“Basically the weight of the ocean helps drive the reverse-osmosis process,” said Kalyn Simon, OceanWell’s director of engagement. “By taking the [reverse-osmosis] process to a place in nature where that pressure naturally exists, we don’t have to create an artificial pressure gauge on land, as we traditionally do in desalination.”
The depth is known as the aphotic zone — a part of the ocean where there is little-to-no sunlight, and where there is less marine life than layers above, she said. Such depths are typically found between three and seven miles off the coast of California, depending on location, which means the project would run through state and federal waters.
The process also produces no brine, Simon said.
Land-based facilities try to squeeze out as much freshwater as possible to help balance high energy costs, with typical targets of 50% freshwater and 50% brine from every gallon processed. But because OceanWell uses “free” pressure from the ocean, it can operate at a lower recovery rate of 10% to 15%, producing a much less salty byproduct that can be dissolved back into ambient conditions within seconds, she said.
A “farm” would consist of multiple desalination pods — 40-foot wide cylindrical cartridges that contain intake pumps — that draw seawater through a semi-permeable filter membrane. The filtered freshwater would be returned to shore through a pipeline, while the seawater outfall would be discharged from the pods into the ocean through a tall column.
“The solution never has time to settle on the sea floor — it goes into the current,” Simon said. “There are no known effects on the ocean at this low of a concentration, and we will be continuing to do studies and environmental tests to continue to prove that.”
The technology is intriguing, said Mark Donovan, chair of the CalDesal advocacy group, who is also the North American water treatment and desalination lead with GHD, an engineering and consulting firm.
“The concept of putting it down at the bottom of the sea floor, deep enough where that hydrostatic pressure can drive the reverse-osmosis process — there’s certainly merit to that,” Donovan said. And by operating at a very low recovery rate, “it’s true they’re not generating as salty of brine as the traditional, land-based system does.”
Desalination was among the technologies outlined in Gov. Gavin’s Newsom’s water supply strategy, released in 2022 amid the state’s driest three years on record. California is expected to see a 10% decrease in its water supply by 2040 because of higher temperatures and decreased runoff, the governor’s plan said.
Donovan said he sees desalination playing a pivotal role in the state’s response to shrinking water supplies. He was glad to see OceanWell gaining traction with a local water district.
“I think it’s very good for the industry and for California as a whole,” he said.