Salt
Water is considered the best source of water, if
accessible, due to the fact that it is generally less contaminated than other
sources and there is an unlimited supply. When considering salt water, however,
the water must be desalinated and disinfected before it is used. This requires
the use of a reverse osmosis water purification unit (ROWPU). Salt water cannot
be purified for individual use.
Ground Water is water procured form
wells and springs. Ground water is generally less susceptible to chemical and
biological pollution than other sources and is considered the best source of
water during an NBC attack. The quantity and quality may be hard to determine
without proper equipment. Adequate disinfectant is required. Ground water may
or may not be used for individual use, depending on its accessibility.
Surface Water is water procured from
lakes, rivers, streams, and ponds. Moving or large bodies of water are
generally considered less contaminated due to the aeration which significantly
decreases growth of bacteria, algae, and fungus. Of the sources of water,
surface water is the easiest to procure for individual use due to it being
readily accessible. Adequate disinfectant is required.
Rain
Water is water procured from rain, snow, or ice. This
source should only be used when other sources of water are not available. It is
not considered a reliable source due to the fluctuation in annual rainfall which
results in inadequate quantities. Adequate disinfectant is required.
3. FACTORS AFFECTING SOURCES OF WATER
Water
Quantity - the source should provide an adequate
supply of potable water for all personnel for the expected length of stay.
Water
Quality - water source should be free of significant
contamination such as sewage, naturally occurring toxic elements, and any NBC
warfare agents. The water should not be objectionable due to turbidity, color,
odor, or taste. Ensure source is protected from possible organic contamination
by sewage fallout or runoff from latrines, showers, motor pools, etc.
Accessibility - the water source should be accessible
and able to be treated with available resources.
4. WATER
DISINFECTION METHODS
Boiling - this method should only be used in emergency
situations and only with small quantities of water, i.e. canteen cup. Bringing
the water to a vigorous boil for two minutes will kill pathogens such as Giardia
and E. coli. This method does not provide for residual disinfectant
capabilities and should not be used to store large quantities of water.
Chemical
disinfection - the three compounds used to chemically
disinfect water are Iodine purification tablets for small amounts (individual),
calcium hypochlorite 56-75% for large amount (unit level), and sodium
hypochlorite, or regular household bleach in liquid form, can be used to
disinfect large and small amounts.
5.
PROCEDURES FOR WATER DISINFECTION IN CANTEENS
Iodine tablets
- Inspect tablets for signs of deterioration. Tablets which are
completely yellow or brown, stick together, or crumble easily are no longer
effective. Tablets should be steel-gray in appearance.
- Add two
Iodine tablets per canteen of water regardless of water color.
- Replace
cap loosely and wait 5 minutes for the tablets to dissolve.
- Shake well, allowing leakage around the threads of the cap of
the canteen to disinfect the threads.
- Tighten
cap and wait an additional 30 minutes before consuming (total of 35 minutes).
- Water will be golden brown in
color.
Tincture of Iodine 2%
- Add 5
drops to a 1-quart canteen, or 10 drops if the water is cold or cloudy.
- Replace
cap loosely and wait 5 minutes for the Iodine to dissolve.
- Shake well, allowing leakage around the threads of the cap of
the canteen to disinfect the threads.
- Tighten
cap and wait an additional 30 minutes before consuming (total of 35 minutes).
Household/common bleach 4-6%
- Add
2 drops to a 1-quart canteen, or 4 drops if the water is cold or cloudy.
- Replace
cap loosely and wait 5 minutes for the bleach to dissolve.
- Shake well, allowing leakage around the threads of the cap of
the canteen to disinfect the threads.
- Tighten
cap and wait an additional 30 minutes before consuming (total of 35 minutes).
REFERENCES
Naval Preventive Medicine Manual, NAVMED P-5010, Pgs 9-4 through 9-10
REV: July 2008
Water Purification Review
1. List the three factors
associated with selecting a water source.
2.
Of the four sources of water, which is best suited
for individual use.
3.
What are the drawbacks to using boiling as a method
of decontamination?
4. What is the total time
needed to disinfect one standard canteen of water using iodine tablets?
