At 02:53 AM 2/18/2002, Andrew Grebneff wrote:
>Reverse osmosis? Osmosis is osmosis; there's no such thing as reverse
>osmosis! It's merely the transfer of elements in a solution across a
>semipermeable membrane, moving from an area of higher concentration
>to one of lower, until the two balance (reach equilibrium). Whichever
>way the elements/chemicals move, it's just plain ol' osmosis. Smells
>of the idea of "deceleration" which is actually acceleration.

Reverse osmosis applies a brine to one side of a membrane, and uses high
pressures to force water molecules through the membrane and out of the
brine, obtaining drinkable water as output.  There are plants with 1000
cubic meter/day output, and there are hand-powered liferaft devices that
produce a pint an hour or some such.  I believe Israel was one of the first
places to use large-scale R-O plants.

The feedwater-treatment plants (around 10 m^3/hour) from Idroconsult
achieve < 0.1 ppm free chlorine, < 2000 ppm total dissolved solids, and
recovery rates (ratio of output:input flows) of 75 or 90 per cent.  Looks
like recovery rates run around 20-30% for "home" units, and 50-75-90% for
industrial plants, and the units are tailored for both input and output
purposes/characteristics -- solids removal, wastewater treatment,
desalination, deionization of municipal water etc.

Google on "reverse osmosis plants" will give plenty of grist if you're
interested.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"