Subject: Expedient Water Filters by Duncan Long

From: [email-masked] (George Guillory)
Date: 18 Oct 1994 18:44:17 GMT

Copyright (C) Duncan Long 1994. All rights reserved.

     EXPEDIENT WATER FILTERS
     Filtering water won't always make it safe to drink.  You'll
need to boil water or use chemical sterilization methods to do that
(See WATER-an Essential).  But filtering can remove large particulate 
matter and even dangerous chemicals that may be in the water.
     The simplest and quickest is to simply pour water through a
sieve made from finely woven cloth.  This will remove large
particles that you can see from the water.  But it won't remove
many dangerous microscopic organisms or dissolved chemicals.  Just
because water "looks" clean doesn't mean that it's safe to drink.
     If you suspect chemical contaminants are in your water supply,
things get tougher.  Probably the best route is to make a simple
carbon filter to clear hazardous materials from your water.  While
constructing one is a lot of work, once it's made you can keep it
going for some time during a disaster--this isn't the case with
many commercial units.
     As you would think, activated carbon (also called activated
charcoal) is the main material needed for a carbon filter. 
Activated carbon is created from coal or wood which has been
processed at high temperatures with steam in the absence of
oxygen.  Activated charcoal (the processed wood or coal) is very
porous and, when broken into small particles, has a large number of
surfaces.  This allows the activated carbon to "latch onto" a
number of chemical compounds so that they become bonded to its sur-
face.  
     You can purchase aquarium activated carbon (at your local five
and dime) and store it for later use.  Keep it in air-tight
containers or it will pick up gas from the air and deactivate
itself.  
     You could make activated carbon by placing wood in a sealed
container with only a very tiny hole in it and heating it until the
wood is charred into activated carbon.  Ideally, a tube leading
into the container would be used to force water onto the wood to
create steam inside the container though this is not essential. 
(The main consideration is to not allow air to get to the charcoal
when it's being heated while having a large enough hole in the
heating container to keep it from exploding when the hot gases in
it expand.)
     Activated carbon bonds with a number of chemicals including
many pesticides (both DDT and Deeldrin), many industrial chemicals
(carbon tetrachloride, PCB's), heavy metals (lead, cadium, etc.),
and many of the dangerous chemicals created by industrial wastes
during chlorination (including chloroform).  This makes it ideal
for many post-disaster pollution problems.
     Bacteria can grow on the surface of wet activated carbon
and--strangely enough--will often grow quite rapidly in the
presence of some of the pollutants removed by the carbon.  To avoid
this, change the carbon regularly to keep from creating biological
contamination of drinking water.   (With regular changing of the
carbon in the filter, the levels of bacteria contamination are
generally believed to be within safe limits for healthy in-
dividuals.  However, the bacteria might adversely affect infants or
those individuals who are sick or weak--which might be the case for
everyone following a protracted disaster.)  
     There's some indication that continued exposure to carbon may
cause cancer in the gastrointestinal tract; be sure to use filter
paper, coffee filter paper, cloth, or other "expedient filters" to
remove particles of activated carbon from your filters water.  
     Making an activated charcoal filter is quite simple.  Probably
the easiest way is to get a funnel, a coffee filter, and a
collecting bottle (or can, cup, jar, etc.) and line the inside of
the funnel with the coffee filter, fill the inside of the filter
with carbon, and DRIP water into the funnel.  As the water slowly
moves through the carbon, it becomes purified and drips out the
bottom.  Boil the water (or use chemicals to kill the bacteria that
may be growing on the charcoal) and the water is ready to use.
     Be sure only a few drips go through the filter at a time and
don't let the water flow between the filter paper and the edge of
the funnel.  Change the charcoal every 3 weeks or after 20 gallons
of water have been filtered.
     As with other water sources, be sure to sterilize the water
after filtering or otherwise removing the fallout from the water
before drinking it.  (See WATER - An Essential) for information about 
sterilizing water to make it safe to drink.)

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The author of this article, Duncan Long, is well-known as the
writer of many gun, self-sufficiency, and survival books.  

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