(2) The surgeon has the responsibility for recommending total chlorine
residuals that will be high enough to assure a free available chlorine residual sufficient
to render water safe. For this purpose, he uses reconnaissance reports and all other
data available on water sources in or near the area in which the use of emergency
water treatment procedures is anticipated.
c. Lyster Bag Chlorination Procedure. The Lyster bag (figure 6-2) is the
familiar 36-gallon canvas container issued on the basis of one bag per 100 men. The
porous canvas permits cooling of the water by evaporation. Small units normally purify
water in the Lyster bag. When using the Lyster bag for disinfection of raw water,
proceed as follows:
(1) Clean the bag and hang it by the supporting ropes. Fill the bag to the
36-gallon mark, which is 4 inches from the top. Use clear, settled water, if possible.
The supports must be sturdy, since the bag filled with water weighs almost 300 pounds.
(2) Empty the contents of at least three calcium hypochlorite ampules
(figure 6-3) into a canteen cup; add a small amount of water from the Lyster bag and stir
with a small stick until a thick mixture results; then fill the cup one-half full of water and
(3) Empty the prepared solution slowly into the Lyster bag, stirring the water
with a clean stick. Cover the bag and clean the faucets by flushing a small quantity of
the water through each of them.
(4) After the calcium hypochlorite solution has been in contact with the
water for 10 minutes, flush the faucets and collect a sample of water from one of the
faucets in the 5 ppm plastic tube for testing (see para (5) below). Place one
orthotolidine tablet in the plastic tube and crush it with the bottom of the orthotolidine
bottle. Place the cap on the tube and shake until the orthotolidine tablet is thoroughly
dissolved in the water. Make the comparison.
(5) If the sample is lighter in shade than the yellow band, the chlorine
residual is less than 5 ppm. Therefore, add sufficient additional ampules of calcium
hypochlorite, one at a time at 10-minute intervals, to the Lyster bag. After each
addition, retest after an additional 10 minutes. When the color of the water in the
sample is the same shade or darker than the yellow band on the five ppm plastic tube, the
chlorine residual is equal to or greater than five ppm. Wait an additional 20 minutes, since
a total contact time of 30 minutes is required. Flush the faucets and check the residual
again before drinking the water. If the chlorine residual is less than five ppm, repeat.