PostHeaderIcon Water Chats — DXV Water Technologies — Desalination in the Deep

Back in 2005 reports started coming out that detailed the progress of oil seeps in the Santa Barbara channel. They’d been around for years but likely it wasn’t PC to mention them. Trouble was — because the seeps were natural — no hue and cry could be raised. Still too many birds were turning up dead. So scientists quietly studied the problem. Recently a study of the seeps has been completed. According to this article
new research shows that natural oil seeps into the Santa Barbara channel dwarf the oil spill of the Exxon Valdez. Remember all the grief Exxon took for the Valdez spill? Well, much much more oil is sitting on the sea floor just offshore of Santa Barbara. Considering that modern oil rigs have taken 20 years of hurricanes in the Gulf of Mexico–without an incident — its not clear to me what all the fuss about drilling off the coasts — is about–especially off Santa Barbara.

Consider that Santa Barbara was the cause of the US being the only country in the world with coastal drilling bans. By drilling — oil companies might take some of the pressure off the under water oil and gas deposits in the Santa Barbara Channel and lessen the seeps. They might also take the some of the pressure off California’s state budget. Might help the feds too.

Funny how this sort of thing doesn’t get out of the science journals.

How does this bear on water desalination? Well readers of this blog know that I’ve advocated doing a test site for underwater desalination off Santa Barbara — by way of a slant well for water drilled alongside a slant well for oil drilled from shore now being negotiated in the area. But if the sea floor just off the beaches in of Santa Barbara is rank with oil –that area might not be best for desalination trials.

Here’s the deal.

These days it seems that no sooner do you mention an idea — than someone’s got a company all set up and with the designs and technologies to implement it. That’s what – DXV Water Technologies has done. They have designed an a desalination process that uses deep water to provide pressure for their membranes.

Now before you close the browser — I think its important to state that everyone has heard of this kind of thing before. The argument against deep water desalination was that you’d need to go down about 1700 or so feet to get the right pressures for the membranes. At those depths — whatever reduction you managed in energy costs would be made up for in maintenance costs. And what the hey–just pumping the fresh water ashore.

So why bother?

I never saw these studies. I only heard about them second and third hand. I’ve been watching the desal research flow for 15 years or so. So I think those studies are old. New technology comes up. According to Forbes

Nikolay Voutchkov of Water Globe Consulting says membranes have gotten 2.5 to 3 times more efficient in the last decade

So its worth taking a second look. DXV Desalination claims they can do the desalination at 850-900 feet. That looks like it tracks membrane efficiency improvements in the last 10 years or so. (ie double the membrane efficiency and half the depth for desalination pressures to work.)Further there are several places off the coast of southern California where you can hit 850-900 feet depths within a mile of shore. The inventor is Diem X. Vuong, He has set up a two-stage nanofiltration process for seawater desalination. Vuong, who retired from the Long Beach Water Department in 2005, developed the ‚Äòdepth exposed membrane for water extraction‚Äô (DEMWAX) process now being tested by DXV Water Technologies. Vuong is familiar with the neighborhood and familiar with the technology. DXV produces almost no brine as it has a 50:1 yield — i.e., 50 gal of seawater for 1 gal of fresh water — AND it occurs underwater, so higher salt dissipates within 1-2m. Makes sense. All they’re doing is pulling a little fresh water out of the vast deep.

They claim their process will desalinate sea water for $0.50/m^3 (616@acre foot). Considering water rates are going as high as 900@acre foot — $0.50/m^3 or 616@acre foot — looks cheap to me.
According to the articles –here’s the money quote:

We can get 50MGD (56TAF/year) from an 11 acre installation. Given a SoCal urban demand of 3MAF, that means that 54 of these systems could supply all of urban SoCal [ignore price for now] — in an area of about one square mile in the ocean.

As well, when you desalinate in the deep dark ocean — the amount of bio fouling declines significantly. Oh and one other thing. It may sound counter intuitive– but desalinated water that comes from these depths is very pure and fwiw — rich in healthy trace elements.

How do you say hmm. Consider. Next year NanoH20 and UCLA Engineering’s Eric Hoek will come out with a membrane that improves efficiencies of current generation membranes.

NanoH20′s Green says the company has modified Hoek’s work substantially to improve and perfect the nanoparticle membrane, but he won’t say how. He says the company is targeting nearly 100% improvement in water production, from 6,000 to 7,500 gallons per day per eight-inch area of membrane to 12,000 gallons per day. The membrane will be the same size and shape as current membranes, so plants won’t have to be retrofitted. The company is building enough capacity to produce “tens of thousands” of membranes–a big plant incorporates 10,000 to 20,000. The first membranes will go on sale early next year.

With those kinds of efficiencies–they might cut costs significantly by cutting the distance to shore or provide all of southern California with water with a half mile square installation at 850-900 feet of water. But more importantly NanoH20 gives DVX cost estimates plenty of room for error–while remaining in the 600@ acre foot range.
For more detail on the DVX project, check out this pdf calledA new approach to Deep sea RO If you have the time and a a more granular interest in the project listen to this mp3 interview with the DVX CEO

The company already has some street creds in the water desalination community. DVX was a finalist –along with Oasys and Aquaporin — at this years Global Water Intelligence and the International Desalination Association awards in Zurich Switzerland.

The prestigious Water Technology Idol award, sponsored by Norit, is particularly poignant as its award is based on votes cast by the delegates present, experts in the field of water and desalination, after a short ‘show and tell’ by each finalist company.


DXV Water Technologies
is interested in doing some tests in fresh water. I don’t think this is really the way to go. There is a very simple way to prove their technology. All you do is bring in the oil companies from off the coast of California. Their shops will already have a very good idea of the capital, maintenance and energy costs of an underwater operation. They’ll know the best materials and processes for every part of the operation except the membranes. They will have streamlined their procedures significantly in the last 15 years. They will already have a detailed understanding of the underwater topography of the area in house–including areass where minor seismic activity might threaten underwater operations.

My wag would be that Maintenance would be the biggest expense.

Energy would still be a significant cost because of the cost of pumping water to shore. I don’t know what would be the cheapest way to bring water ashore from a mile away. For example a slant well drill drilled from onshore — that goes out a mile would be much more expensive than laying a pipeline on the ocean floor. The oil industry can lay 3 kilometers a day of pipeline along the ocean bed. However, a slant well could make the water run downhill to shore. How does that happen? The drill would be onshore. It would drill down say 1500 ft and then slope upward gradually to a point out in the ocean at 850-900 feet. The water from the desalination modules would run down hill to shore arriving at depth of 1500 feet. Equalizing pressure would bring it to 850-900 ft. How would you bring it the rest of the way to the surface naturally. Beats me. The point of having such a steep slope to shore would be to create a lot of forward momentum for the water. You wouldn’t want to lose that momentum at the up elbow onshore with a joint that turns at a sharp angle. They might be able to narrow the diameter of the pipe as it comes shoreward so as to increase the column pressure on the water as it comes ashore. Materials advances in the surface of the pipe might help reduce the friction and drag on the water as it moves forward. The net effect would be increase the pressure on the water as it comes ashore to cut the cost of pumping water ashore over time. If you must still pump the water to the surface you might site the pump down in the well on land to push the water up. Presumably the maintenance and energy costs of such a pump on land would be cheaper than a pump out at sea.

Permitting for the project would be fairly simple since the site would be at sea. There wouldn’t be any disposal issues. If onshore delivery were not energy intensive — there would be no worries about cracking an already strained grid.

Actuallly building a small scale experimental installation would consist of of a set of procedures about which the oil companies have decades of experience: One ship lowers a prefab desal plant & pump to the ocean floor. One ship runs a pipe to shore. One ship runs an electrical line from shore to to pump. An underwater crew attaches everything. Yr done. So instead of taking 10 years from permitting to building–the actual process from permitting to project completion could take one year.

As it happens the oil companies have decades of experience with each one of the procedures listed above.

Likely the oil companies wouldn’t be too interested in going out on their own to fund an experimental project outside of their field. Funding for the experiment might come from Title XVI funding for the DOI. This is the sort of project that might answer the 21st Century Bureau of Reclamation question….how do you top the Hoover Dam.

Or funding could come from the vast pools of dollars for R&D controlled by DOE that nobody in the desalination industry knows how to tap–or from a utility funding authority set up this year. No matter where the dollars came from–they would be federal dollars well spent.

Update: Science Daily is calling a UCLA based company a big breakthrough desalination testing.

With these critical issues looming large, researchers at the UCLA Henry Samueli School of Engineering and Applied Science are working hard to help alleviate the state’s water deficit with their new mini-mobile-modular (M3) “smart” water desalination and filtration system.

In designing and constructing new desalination plants, creating and testing pilot facilities is one of the most expensive and time-consuming steps. Traditionally, small yet very expensive stationary pilot plants are constructed to determine the feasibility of using available water as a source for a large-scale desalination plant. The M3 system helps cut both costs and time.

“Our M3 water desalination system provides an all-in-one mobile testing plant that can be used to test almost any water source,” said Alex Bartman, a graduate student on the M3 team who helped to design the sensor networks and data acquisition computer hardware in the system. “The advantages of this type of system are that it can cut costs, and because it is mobile, only one M3 system needs to be built to test multiple sources. Also, it will give an extensive amount of information that can be used to design the larger-scale desalination plant.”

The M3 demonstrated its effectiveness in a recent field study in the San Joaquin Valley in which it desalted agricultural drainage water that was nearly saturated with calcium sulfate salts, accomplishing this with just one reverse osmosis (RO) stage.

If they can figure out a way to put their mobile testing tools underwater they might merge well with DVX to create a fast pilot.

I

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