D. The pH is read directly on the
your eye and face a good
color disc. Value of this sample
light source. Rotate color
disc until a color on the disc
matches the color of the
sample in the tube.
Figure 2-5. Color comparator for determination of pH.
2-12. UNIT CHLORINATION
a. Lyster Bag Chlorination. Water is disinfected at the unit level by using the
Lyster bag (see figure 2-6) or other suitable container and ampules of calcium
hypochlorite that are provided in the chlorination kit (see figure2-2). The procedure for
the chlorination of water in the Lyster bag is as follows:
(1) Clean the bag and hang it by the supporting ropes as illustrated in
figure 2-6. The supports must be sturdy, as the bag filled with water weighs
approximately 300 pounds.
(2) Fill the bag to within 4 inches from the top (the 36-gallonmark). If
possible, use settled, clear water.
(3) Put the contents of one calcium hypochlorite ampule into a canteen cup
(or the contents of as many ampules as necessary for the color to reach the required
5 ppm per mg/i chlorine residual), 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 stir again.