US subsea RO desalination project tackles scarcity

Water Farm 1 to deliver water security to millions

Water Farm 1 (WF1) is projected to deliver up to 60 million gallons of water every day by 2030, supplying more than 1.5 million residents with drinking water. 

Six additional California water agencies are joining the effort, which, once operational, will deliver water security to the region.

 

California faces tough water challenges

California, the fourth-largest economy in the world, faces tough water supply challenges. These are exacerbated by recurring periods of drought and the over-reliance on imports and water taken from the Colorado River, which faces scarcity issues and uncertainty surrounding extraction rights. As a result, the state is investing heavily in desalination projects. 

OceanWell’s CEO, Robert Bergstrom, told Aquatech Online: “The state is concerned by the environmental issues surrounding traditional means of desalination. Our approach fixes those perceived issues, so California can access the ocean in an eco-friendly way.”

 

What is Water Farm 1 and how will it work?

Locating desalination pods offshore is becoming more popular as the technologies involved move from prototype to commercial reality.

Water Farm 1 will be located 4.5 miles off the coast of Malibu, California. Once fully operational, the farm will consist of a network of self-contained pods placed 400 metres beneath the Pacific Ocean. The pods will utilise natural ocean pressure to reduce energy use by up to 40 per cent and eliminate harmful brine discharge.

Bergstrom added: “Southern California is uniquely suited for subsea desalination because the continental shelf drops quickly, giving us access to the deep ocean pressures we need just 4.5 miles off the coast.”

 

From prototypes to commercialisation

OceanWell completed its prototype testing in 2021 at the US Navy's Deep Ocean Simulation Facility. 

“Since then, we've steadily advanced towards commercialisation,” Bergstrom explained. “Earlier this year, we launched our pilot with the Las Virgenes Municipal Water District – the first submerged RO desalination pilot in the US – to validate our LifeSafe intake system.”

These early stages of testing took place in bio-active freshwater conditions, which were purposefully chosen to be much more challenging than those the farm will face in the deep sea. 

“This gave us solid insights into filtration performance and materials and helped inform the design of each further stage before ocean deployment,” added Bergstrom.

 

What hurdles and challenges does a deep-sea desalination plant face?

Initial challenges came in the form of convincing investors to take on a new idea. This required proving the individual processes worked and that the whole system worked over extended periods.

The biggest challenges now, as Bergstrom explained, are permitting, infrastructure planning, raising the required capital to move operations offshore, and integrating offshore and onshore delivery systems.  

“That’s why our seven-agency consortium is funding an independent feasibility study to evaluate how best to integrate Water Farm 1’s output into California’s regional systems,” Bergstrom added.

On the environmental side, OceanWell has formed Tribal and Environmental working groups to ensure its design addresses ecological issues, such as preventing marine entrainment and limiting brine impacts.

 

How does Farm Well 1 handle brine discharge?

California’s regulatory requirements allow for brine dissipation to about 105 per cent of the natural background level within 100 metres of the desalination facility. Traditional desalination has a recovery rate of 50 per cent, which leaves a highly concentrated brine. In response, OceanWell is running a system with a 5 to 15 per cent recovery rate, producing a mild brine. 

“Our brine is so benign that modelling tells us we can do 10 times better than required within the first few metres. This is a game-changer,” began Bergstrom. “The reason we can run the recovery rate so much lower is due to the economics of pressure. For an onshore system, most of their electricity is used to create pressure to overcome the osmotic head, i.e. to push water through the membranes. That is energy-intensive and costly.”

He added: “OceanWell, on the other hand, has access to an unlimited, constant pressure, and it’s free. When you remove that power cost, you can focus on what’s ecologically safe and drop the price of water at the same time.”

 

What does this mean for water security in California?

Water Farm 1 has been designed to relieve the pressure on overstressed systems, such as the Colorado River and the Bay-Delta. By 2030, it is expected to provide up to 60 million gallons per day to Southern California, a meaningful new supply that diversifies the portfolio and improves resilience. 

California shares its Colorado River rights with other states located further upstream. These rights are extremely complex, and with many states also suffering from water scarcity and rising demand for water, adding a new, climate-aligned source of drinking water is more than welcome. 

Bergrstrom explained the implications: “This means that providing more water at the coast would allow California to ‘swap’ water with states further inland, meaning each state gets more water, without the need for a long pipeline physically conveying the water inland. 

He added: “We call this ‘water exchange’. This exchange is more efficient because it also reduces pumping and evaporative losses that would occur if the water were being physically transported. Therefore, this new supply of water from OceanWell has major benefits, not only for California, but for the water future of the entire Colorado River basin as well.”