[Philmont]: Water Treatment

Hi all,

This topic has started to stray just a bit from my original questions, but
that's ok. I thought I would present some information. I am not a
credentialed expert in water treatment, but I have a high degree of
confidence in the statements to follow.

Treating back country water for human consumption involves getting rid of
three general categories of contamination: suspended solids (muck, dirt,
sand, etc.), chemicals (petroleum, pesticides, heavy metals (Arsenic, mine
tailings) and the like, and biological agents (bacterial, viruses, cysts).

Boiling ("the most certain treatment" - Philmont Guidebook to Adventure)
will kill all biological agents. The technique is to get the water to a
rolling boil. The combination of heat and time required to get to that
point is sufficient. Boiling does not remove suspended material nor does it
remove chemicals.

There is an important distinction between "filters" and "purifiers."

Filters generally will remove suspended material, many chemicals and most
will get most bacteria. Filters force solution through very fine holes
(pores), eliminating stuff that's bigger than the holes. The most popular
portable filters sold today have pore sizes of 0.1 to 4 microns.

The Giardia cyst (a common intestinal parasite) is 6 microns in diameter and
many bacteria are larger than 0.2 microns. Small pore filters (at
least 0.2microns) can remove such organisms. Viruses, however, range
from
0.004 to 0.06 microns in size -- far smaller than the pore size of the best
portable filter.

Note that while cysts are among the easiest biological agents to filter,
they are among the hardest to kill via non-mechanical methods (heat,
chemicals).

Purifiers must be certified by the EPA for sale in the US. The EPA is
involved because most methods of purification involve chemicals. Purifiers
remove biological agents, and usually filter as well.

There are a number of purifier devices on the market. Most use a chemical
treatment to kill biological agents, frequently in combination with a
filter. For example, the "MSR Sweet water Purifier System" adds a "purifier
solution" to the water after it has been filtered by the machine. The PUR
Hiker includes an "iodine matrix" in the filter mechanism.

The MSR MIOX converts a brine solution to a mixed-oxidant solution via
electrolysis. Note that this product generally lacks filtration.

Polar Pure (Philmont's old method) will kill all biological agents. Under
some conditions it may take several hours. Does not remove suspended
material nor does it remove chemicals. Leaves an iodine taste, which some
find objectionable. http://www.polarequipment.com/page2.html

Micropur (MP1) was developed as a second step after filtration to eliminate
remaining biological agents. As with Polar Pure, it will kill all
biological agents, given proper concentrations and enough time. Based on
chlorine (like most municipal water systems), there is generally no
aftertaste. Does not remove suspended material nor does it remove
chemicals.
http://www.katadyn.ch/site/us/home/outdoor_products/our_products/ultrlight_series/micropur_mp1_tablets/

There is at least one purifier that employs a non-chemical method to
eliminate all biological agents, the First Need product.
http://www.generalecology.com/portablesystem.htm

So, boiling, Polar Pure and Micropur MP1 will kill biological agents, but do
not remove suspended material or chemicals.

Filters remove suspended material and chemicals, and most biological agents,
but not all.

Purifiers remove biological agents, and most also remove suspended material
and chemicals, depending on the associated filtering system.

Perhaps the biggest difference between filters and purifiers is removing
viruses (filters no, purifiers yes). There is an on-going debate about the
prevalence of viruses in back country water sources, and thus the need for
"purification." Most viruses are species-specific, and a lack of human
activity in the "back country" would argue that there is little need for
virus purification.

I think the heavy human use of Philmont would argue against that
proposition, and in favor of treating for viruses.

Neal Osborn
SCCC 2006

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Received on Wed Mar 22 17:37:59 2006