(2) Disinfection. Disinfection refers to the treatment of the water with
chemicals or by boiling to destroy disease-producing organisms.
(3) Chlorination. Chlorination is the disinfection of water by the addition of a
chlorine compound such as calcium hypochlorite.
(4) Chlorine dosage. The chlorine dosage is the amount of chlorine added
to a given quantity of water.
(5) Chlorine demand. The chlorine demand is the amount of chlorine that
reacts with, and is consumed by, organic material, bacteria, and other substances in
water. In other words, it is the amount needed to kill the organisms living in the water.
(6) Chlorine residual. The chlorine residual is the amount of chlorine
remaining after the demand has been satisfied. Dosage minus demand equals residual.
(7) Parts per million (ppm). Parts per million is a unit of measurement for
expressing the number of units of a substance in one million units of water by weight.
Another way of expressing ppm is milligrams per liter (mg/l).
b. Chlorination Requirements. Sufficient chlorine must be added to water to
produce a given chlorine residual 30 minutes after the chlorine is added to the water. A
five-ppm residual is the standard requirement for field water supplies. Higher or lower
concentrations, however, may be prescribed by the command surgeon based on his
knowledge of local diseases and environmental conditions. The minimum field
requirement for the chlorine residual is one part per million (1 ppm).
c. Chlorination Kit. The chlorination kit (figure 2-3) is available to all units for
use in chlorinating water and testing it for the proper chlorine residual. The kit contains
calcium hypochlorite 0.5-gram ampules for disinfecting water together with three plastic
tubes and three vials of orthotolidine tablets used in determining the chlorine residual.
The vials of orthotolidine tablets are packed inside the plastic tubes. Each plastic tube
has a band around the tube and each band is a different shade of yellow. The lightest
shade of yellow is used to test for a one ppm level of residual, the medium shade is
used to test for a five ppm level of residual, and the darkest shade is used to test for a
ten ppm level of residual. These figures (1, 5, and 10) are printed on the tubes.
Sometimes the five-ppm tube is not numbered.)
Figure 2-3. The chlorination kit.