wind driven desalination

[electrondady1]

the water is good around here but lots of places have problems
glacial fed rivers appear  to be drying up,  incredible chaos may follow

Drinking with the Wind: Wind-Powered Seawater Desalination
http://www.treehugger.com/clean-technology/drinking-with-the-wind-wind-powered-seawater-desalination.html

[dnix71]

Seawater reverse osmosis desal is much tougher than it looks. There is a lot of suspended sand and organic stuff in sea water that clogs the membranes. That's why Tampa, Florida's plant has taken so long to get to work and still doesn't put out all that much. Salty well water is much easier to R.O. Lots of cities in south Florida desal large amounts from the Floridan Aquifer. The Biscayne is fresh water but there are legal limits/agreements on the draw and it runs dry some years when it doesn't rain enough.

[electrondady1]

the reverse osmosis method must be high energy input.
i've seen military units that work on any kind of nasty water.
but their mostly for emergency/disaster stuff.

from what i understand of the 7 billion of us there are now
fully one billion are starving.
a cheap method of desalinization could be a growth industry very soon or maybe now .
i've read that there are lots of briny ground water sources in the world
 especially in deserts.
 even using some kind of captured water vapour evaporation method might be
helpful.

 

[phil b]

I assume that some salt in the finished water is acceptable, IMHO. Not to the point of as much salt as a water softener leaves though. It tastes bad.

The water I have tasted from RO units have almost no taste. That's why the bottles water companies add minerals and salt to their products before it gets out the door.

So, how much salt is acceptable?

[damian]

I'm sure I could build one.  If there were, say, an NGO looking to do this I might be interested. 

[altosack]

The reverse osmosis method is not very high energy input, especially compared with distillation.  It does require a relatively high inlet pressure to produce high salt rejection.  There are "low energy" membranes that work tolerably well with 100 psi.  I designed and built a system with these that produces about 0.6 gpm (up to 850 gpd) for about $1000, and I run it at 150-160 psi to get 99% rejection (reduction from ~350 ppm to ~2-3 ppm), and a recovery of 70% with recycle.  This takes about 180W from a 1/2 HP pump, so it's about 5 Wh/gal.

It also is not that difficult with "dirty" sea water; it just needs to be prefiltered (changing sediment filters often is cheaper than changing RO membranes !), and it needs to have at least 2 stages to get the salt content low enough.  I haven't built one for sea water (I live > 500 miles from the nearest salt water source), so take it with a grain of salt, but I learned a bit about it when researching the one I did build.