I bumped into this one while running around, for about $64.00 you could throw one of these in your BOB (if you live near the ocean or going on any boat cruises)in the event salt water is your only source for water.

I had bought PUR Survivor 35 Water maker awhile back since I live near the ocean and lugging it around is definitely a pain (8 lbs). I know you can get a lot of military surplus from e-bay from time to time, the one I bought (PUR 35) was normally $1,895.00 new, and I got it off of e-bay for $200. It had never been used and still had biocide in it with the military annual inspections. Tried it out in Daytona Beach and it worked like a champ. Heavy thing though, but if I went on a boat cruise I would be interested in the Sea Pack. (Easy storage, light weight and very versatile)

Sea Pack

Hmmm, interesting. Using concentrated sugar to draw water from the salt.

-Blast

I think you could build a static pressure filtration device that would work as well as, or better than, the osmotic pressure system described here. A constant positive pressure across a desalination membrane should work. I can imagine a bladder system that sits in the bottom of the liferaft. You fill it with a few liters of seawater, then cap it and lay on it for a couple hours. The gravity load should be sufficient to drive the fresh water through the membrane. Then instead of sugar water, you just have plain water.

I don't think you would get anywhere near enough pressure with just body weight on a large bladder. The weight would be distributed over too large an area. There must be some reason why no one has designed a simple bladder type reverse osmosis system yet. Perhaps the pressure required is so great that it would burst the bladder(imagine standing on or jumping on a hydration pack-I imagine something like that would be required to generate enough pressure-which of course you couldn't do on a life raft anyway).

You may be right. Based on further calcs, it looks like you'd need about 400 psi across the membrane at a minimum(based on the fact that seawater has an osmotic pressure of about 27 atm). I suppose you could use a lever of some sort, combined with the rolling motion of the water. It might be easier to use a centriuge system, although it would not be as passively operational as a shifting static load would be. A manually driven centrifuge would likely require more effort than it is worth.

My calcs could be wrong. Even though I am working on a big RO plant, I am not an engineer. I will have to ask the experts tomorrow and get back to y'all with this one.

What about the military's old "De-salting" kits? They were still packing them in RSSK's back in the early 1990's.

Yep, checked with the engineers this morning, and 400 psi would be the absolute minimum pressure it would take to desal using RO. We are running about 300 psi to get the flow rate up high enough on our recycled (brackish) water system, and the desals typically run at 50 atm, or about 800 psi to generate sufficient flow.

At this point, I think the only manual method that would generate the amount of water required would have to be centrifugal.

The desalter kits have all been replaced by reverse osmosis units. You won't find many on the market unless they were liberated from the military because DRMO has the desalter kits sent to a metal recovery processor to recover the silver from them.

The military desalter kits causes most of the salt to chemically precipitate out of the water. It's better than nothing, but you'll end up with water that is still a little salty.

If Falcon5000 obtained an MROD (manual reverse osmosis desalinator) that was mil issue, then whoever sold it had "liberated" it from the military because none have been sold surplus, yet...

Although he shouldn't worry about anyone knocking on his door about it because there currently is a glut of these in the Navy.

Regards,

Tom