On Monday, I visited DXV Water Technologies, a start-up with a new technology for desalination.
I met with Michael Motherway (president), Curt Roth (VP engineering), and Diem Vuong (inventor), and we discussed their technology, markets and other issues of supply and demand. Here's one write up [PDF].
I HIGHLY recommend that you listen to this MP3 of our conversation (just over an hour; 22MB). It's rambling and rambunctious and full of interesting details from the world of "entrepreneurial water" -- often an oxymoron.
Their technology uses off the shelf micro filters in a new (patent pending) configuration that is placed 270m underwater in the ocean. The hydrostatic pressure at that depth is enough to push fresh water through the filter, at such a slow rate and yield that there is no energy required (energy is necessary to bring the water onshore) and entrapment of biological beasties and brine concentrates are minimized.
Their system can use any size filter to get water that's clean of not much (for prefiltering) to water that's free of endocrine disruptors (the current bad-boy of water quality). [The second slide is slightly fuzzy but it shows the relationship between pore size and what's filtered. Vuong said that IF their filter hole was as big that of a straw, then a virus would be the size of a bus and an endocrine disruptor would be the size of a softball, i.e., still blocked from passing through.] The system can also be used to clean fresh water and/or reclaimed water for consumption.
Because DXV's system uses 1/3 the energy of current systems, it produces water at half the total cost (capital costs are the same), i.e., $0.50/m^3. DXV's cost will ALWAYS be lower than on-shore, high-pressure desal because both technologies use the same filters. It's the method of holding the filters that differs.
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.DXV is looking for $1-2 million to run a fresh-water pilot of their technology. Tell them I sent you :)
Bottom Line: Technology CAN lower the price of supplying water, but remember that the easiest way to end a shortage is to increase prices to reduce demand -- and higher prices also generate revenue, not costs!
12 comments:
I have a couple of questions and a little food for thought to offer regarding your post today about DXV desalination. (I should preface all this by saying that I have no formal training in economics, but I do have an educational background in the natural sciences. I've also become educated regarding a variety of water issues as the result of working on a comprehensive documentary project (in progress) relating to the Salton Sea, the Imperial Valley, the Colorado River, and the many complex ecological and water-related topics involved in those subjects. I should also admit that I haven't yet listened to the MP3 of your full conversation with DXV.)
So, regarding DXV desalination: What happens to the highly concentrated brine produced during their oceanwater desalination process? How much brine is produced per volume of fresh water produced per unit of time? What happens to the brine? Assuming the brine is simply discharged into the ocean, what effects on marine ecosystems will the brine have? Since you seem to be a very well-informed person, even on a variety of non-economic issues, I'm sure you're aware that our oceans are already in a state of crisis that is only expected to worsen. Species at every level of ocean ecosystems practically world-wide, from primitive algae and the tiniest invertebrates to the largest whales, are already affected by such factors as pollution, over-fishing and destructive harvest methods, and -- perhaps most important at this point and into the future -- the insidious and ultimately devastating impacts of climate change (e.g., ocean acidification). You're probably also aware that concentrated brine is very bad for marine ecosystems. So, is introducing large quantities of concentrated brine into already-stressed marine ecosystems really the answer to our fresh water problems, especially in southern CA? Wouldn't it make more sense to acknowledge that for the past century we have engaged in an insane approach to development in the arid West, and conclude that our future water policies and technology investments should not -- either directly or indirectly -- continue to support and encourage more thirsty development and ongoing population growth in a naturally waterless region? The notion that larger and larger populations in arid locations can continue to be sustained -- if we can just find the (non-existent) silver bullet for production of more fresh water -- is misguided, isn't it? Solid scientific data predict that the southwestern U.S. from Kansas to California will become a permanent Dust Bowl by 2050 due to climate change, unless global emissions of CO2 and CO2-equivalent greenhouse gases are immediately controlled and significantly reduced very quickly. Even assuming there will be rapid control and reduction of human GHG emissions moving forward, due to the quantity of GHGs already in the atmosphere and the feedback effects caused by them it appears highly likely that the U.S. southwest will suffer permanent drought conditions worse than what we've had so far. It would seem to be quite imprudent to expend significant resources on developing new technologies that simply perpetuate our misguided development of huge population centers in arid regions without regard for lack of water, particularly when such technologies also have serious potential to cause other, new ecological problems.
On the other hand, using the DXV technology to "clean fresh water and/or reclaimed water for consumption," as you mention, does seem to be a very worthwhile undertaking. (But it's unclear to me how the same technology could be used for both oceanwater desalination and those other purposes, since the DEMWAX oceanwater desalination process seems to require significant hydrostatic pressure only available at great depth.)
JER -- 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
I AGREE that we shouldn't be living in arid areas, and that cheap supply can make that worse. HIGHER prices can offset that problem, but they have to be based on value, not cost.
Fresh water purification takes place at 20m.
Listen to the MP3 :)
Hi David,
I love your concern for water issues.
I am starting a new blog on water issues out of Nevada. Will be co-writing with my friend and colleague Michelle. We are both on the environmental journalism grad program at the Reynolds School of Journalism at Uni of Nevada, Reno.
Like you, I am an economist by training, but unlike you I am a very rusty economist because I have spent almost all my years working on other issues like safety and preparedness.
I will like to keep in touch with you on water issues in our region.
Check out our blog: envjournal.com
Keep the pacesetting work!
Gideon
Reno, NV
The one significant hurdle to de-sal in my opinion outside of cost is the site requirements, try finding 11 acres anywhere in Los Angeles that could support such a facility. Don't say Hyperion or Scattergood. Both sites have little free land to offer.
@westchester -- the "desal plant" is IN THE OCEAN!
I am not sure I understand how this works. If hydrostatic pressure is used to push water through a membrane it means that the pressure on the other permeate side of the membrane is low. Since the membrane is at the bottom of the ocean the permeate side must be isolated from the hydrostatic pressure like in a rigid container. Then, how will it be brought to the surface level. One needs to apply energy to lift it against the same hydrostatic pressure.
@Anon -- you are right about pressure, but the answer to your question is in the post, i.e., "there is no energy required (energy is necessary to bring the water onshore) "
No really. Your depth is designed to overcome the osmotic pressure. So even if the "snorkel" idea lowers the pressure on the back side of the membrane(I haven't figured this one out), your submersible pump will need to provide the 850 feet of pressure to get back up to the surface (370 psi + piping friction (miles?)) all with seawater duty materials at a fairly inaccessible location. Hello? Sponge Bob?
Can you imagine a building permit to run medium voltage at this scale so far off-shore? Seems pretty sketchy.
I'm not an engineer or economist, but I do follow the energy industry... The challenge of transporting sufficient energy to the site is real... question...could you use co-located combinations of sub-sea tidal/current/geothermal power generators in conjunction is other floating alternative energy sources (solar/wind) to generate enough energy (See link to "energy island" http://ultrafutureworld.com/2008/08/18/sustainable-modular-islands/ ) to pump the water to the surface? Also, sub-sea pumping systems already exist in the oil/gas industry...
Would something like and engergy island (see link) solve the energy question?
http://ultrafutureworld.com/2008/08/18/sustainable-modular-islands/
Also, the oil and gas industry has the pump technology to get the water to the surface...
A problem I can foresee with desal for Southern California is that the coast is at the lowest elevation and thus desalted water would need to be pumped uphill to even adjacent coastal cities. The energy cost for the pumping would likely be significant.
The existing water distribution and conveyance system brings river water to Southern California by a combination of pumping and gravity flow.
I'm not pipeline hydraulic engineer but it would seem to me that existing pipelines may need to be retrofitted to pump water in reverse of its customary gravity flow. I can imagine this also would be costly. And how would uphill pumping and gravity flow pumping coexist in the same pipe?
Maybe some expert can answer this.
The energy consumption is NOT lower for this technology. It used to be 10 years ago. However all newly constructed "on shore" desalination plants use "energy recovery devices". These recuperate all energy except the one that is necessary to drive the desalination process. (if you google for Energy Recovery Inc, you'll see what I mean). The "in ocean" technology needs the same amount of energy to drive the desalination process, since this depends on osmotic pressure and thus on the salinatiy of the water. Yes, the "in ocean" process requires less pretreatment, but the disadvantage is to have to install a very large installation on the seabed, this will be very costly. Comparing apples for apples the "in ocean" variant has the advantage that it takes water from a considerable depth, at this depth you'll have very little sealife, so the impact on the marine biology will be lower. Disadvantage of taking water from great depth is that the temperature is lower. Therefore viscosity wil be higher. The energy consumption of reverse osmosis is strongly influenced by viscosity, so energy consumption will actually be higher, not lower. Desalinating seawater can be made an environmentally freindly as you want it: renewable energy, fish friendly etc etc, hower all of this will cost additional money. As long as desalination projects are being tendered on price alone, everybody will chose the cheapest option.
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