GOOD POTABLE WATER DEVICE

From: hpn
Newsgroups: misc.survivalism
Subject: Re: Recommend a good potable water device?
Date: Mon, 01 Jul 1996 12:31:35 GMT

Geri  wrote:

 MMedi13720 wrote, suggesting painting a pressure cooker black and 
 allowing solar heat to distill water. Then he wrote,

   I don't see it taking any longer than a regular solar still (as in
   visqueen, a bucket, and a rock), not if you paint the cooker with black
   barbecue paint. Maybe a bit longer....snip
   
   Mike S.

 Though the solar heat absorbed by a blackened pressure cooker would 
 increase the rate of evaporation inside the pot, there are a couple of 
 reasons that it would not be an effective distillation apparatus for 
 more than a bit of water without providing additional heat.

 First,  distillation is dependent on water reaching the gas phase and then 
 recondensing within the cooler tube or coils that then take the droplets 
 down into a collection container. Though more water would become vapor 
 in a sun-warmed pot than a cooler one, the surface area through which 
 those randomly moving water vapor molecules must travel, i.e., the small 
 hole at the top of the pressure cooker, would mean that a very small 
 number of molecules would actually exit the pot into the tubing. 

The  majority of them would bounce against the top and sides of the pot and, 
 many of these would condense again, dripping back into the water below. 

 This would especially be true if there was any moving (cooling effect) 
 air around the pot. In a classic, visqueen, solar still, the surface 
 area for evaporation and condensation is much greater and would result 
 in a more sizable collection of water. In order to drive the water vapor 
 molecules through the hole at the top of the pot with any further degree 
 of efficiency would require the addition of much more energy (heat) 
 which would increase the pressure of that vapor phase above the water, 
 forcing more of the molecules to travel out of the hole and diminishing 
 the probablilty of their condensing on the lid of the pot. 

The entire  pot would be hotter and the lid would be less likely to serve 
as a cooling,hence condensing, surface. The placement of the pot in a 
parabolic-type solar cooker would increase the concentration of solar 
energy hitting the pot and could work, but it would have to be quite a 
large cooker, IMO. The pressure cooker could be an excellent 
distillation device if sufficient heat was applied to meet all of the 
conditions, above...Geri Guidetti, The Ark Institute

In article <4r8jmq writes:

I just found a purification kit for about $50.  It is really compact
and it does 1,000 gallons of water.  You only need to put a small
amount of Clorox in the water to kill bacteria and the kit will filter
that and other contaminants out.  It is really easy to use and it
requires no power to operate.

How does it work? Unless there's something besides bleach, it'll get rid
of bacteria, but not protozoans, viruses, VOC's or heavy metals.

According to the documentation, it uses a blended carbon filter to
remove everything that the chlorine doesn't kill.  It also removes the
chlorine or iodine.  To use it you take it apart and pour water into
the top of the unit.  You let it filter through and collect in a
receiver at the bottom.  Just remove the receiver and drink.  The
exact size is 6"x3" and it weighs one pound.