Re: purifying water....page 1 -- Food Storage & Self-Reliance Forum

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Date Posted: 13:03:04 10/17/99 Sun
Author: clover
Subject: Re: purifying water....page 1
In reply to: clover 's message, "purifying water" on 18:14:46 10/15/99 Fri

....i found this a long while back..i cannot vouch for it's accuracy ,but i know most of what they say here is common knowledge among backpackers...
clover

Backcountry Drinking

--Why Not Just Drink the Water?

In the Great Outdoors, there are potentially four dangers of drinking
water straight from a source (assuming it's freshwater): chemical
pollutants, protozoa and larger parasites, bacteria, and viruses. In this
panel, we will first discuss a few of the
methods used in the backcountry to avoid these dangers, then give a brief
description of the toxins and pathogens found in water, and which method
is best suited to neutralizing each.

--Methods of Purification
The oldest (and cheapest) method of purifying water is to boil it.
Boiling for five minutes will kill any biological hazards you could expect
to find. Most pathogens are actually long dead by the time the water
boils, but the five minute boil will g et them all (remember to add 1
minute to this time for each 1,000 feet above 10,000 feet). Boiling will
NOT neutralize chemical pollutants.
Chemical purification involves the use of iodine or chlorine to
kill the nasties in the water. This method is lightweight and relatively
inexpensive, but will not neutralize chemical toxins. In addition, you
must make sure that water at 25 deg. C (7 5deg. F) sits for 20-30 minutes
with iodine in it for purification to take place. If the water is colder
(as it usually is), you will need to let it sit longer - possibly
overnight for cold stream water. Warm the water against your body or even
on y our stove if you want it to be purified faster. Once the appropriate
time has elapsed, the "band-aid" taste of iodine can be neutralized with a
small amount of ascorbic acid (vitamin C). Used properly, iodine will
kill most protozoa and all bacteria and viruses in water. After prolonged
use, some people develop thyroid problems, so be aware of this potential
side effect.
The latest rage in water purification is the use of filters, and a
large number of them are available (see the review later in this panel).
There are a couple of things to bear in mind when shopping for filters.
First, only a system which includes a n iodine matrix will kill viruses
(see below). Second, a filter with pores larger than 0.2 microns - note
the location of the decimal point, as it is important - will let bacteria
through. The advantages of a filter are quick processing time (don't have
to wait for the pot to boil or the iodine to do its work) and
clean-tasting water (no iodine or vitamin C flavor). Some systems also
contain a carbon filter which will remove chemical toxins.
Finally, one system seldom used by hikers, but carried on seagoing
boats and possibly sea kayaks, is the reverse osmosis, or RO filter.
These systems are bulky, heavy, and expensive, but they will desalinate
seawater - a useful thing to be able to do
on a lifeboat, for example. Such filters will also remove all biological
contaminants, including viruses (viruses are considerably larger than the
exclusion limit of the RO filter).

........end page 1....

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Re: purifying water...page 2 -- clover, 13:05:31 10/17/99 Sun