(a) Coliform organisms are present in fecal wastes on the order of 1011
to 1013 per capita per day. They are roughly 100,000 times more numerous than
(b) Coliforms are found in both natural and treated waters where
contamination has occurred. The optimum conditions for their survival are about the
same as for pathogenic organisms.
(c) The coliform group may be identified and counted by relatively
simple laboratory procedures.
(d) The coliform bacteria are not, in themselves, pathogenic to adults;
therefore, they present little hazard to the laboratory technician who works with them.
COLLECTION OF SAMPLES FOR BACTERIOLOGICAL ANALYSIS
a. Sample Bottles and Collection Points.
(1) Samples of water for bacteriological analyses must be collected in sterile
bottles. Screw cap bottles of about 120--miIIiIiter capacity are preferred, but glass-
stoppered bottles are acceptable. These bottles must have been cleaned; capped with
a protective hood of paper, foil, or cloth; and sterilized. The sample bottles are normally
provided by the laboratory that performs the bacteriological analyses. This laboratory
also places in each bottle 0.02 to 0.05 grams of sodium thiosulfate, a reducing agent to
neutralize any chlorine residual which may be in the water at the time of collection.
Such neutralization prevents the chlorine from killing any living organisms in the water
samples after collection. If necessary, the laboratory provides standard cardboard and
metal mailing tubes in which the bottled samples can be sent through the mail. If
sample bottles are prepared by the agency collecting the samples, they should be
sterilized in an autoclave at a temperature of 121C and a pressure of 15 pounds per
square inch for a minimum of 15 minutes. If sodium thiosulfate is used (required only
for samples of chlorinated water), it must be added prior to sterilization.
(2) Samples from the potable water system should be taken at points that
are truly representative of the water flowing in the system. These locations on most
posts would be kitchens, dining halls, barracks, administrative areas, hospitals, clubs,
snack bars, family quarters, and other locations where water is consumed.
Occasionally, special samples, for reasons determined to be important by the surgeon,
may be collected from raw water sources and from water in various stages of the
treatment process, at dead ends, or at infrequently used points of the distribution
(3) Normally, samples are taken from cold-water faucets, which are used
frequently. Do not take samples from hot water faucets. Most of the residual chlorine
will dissipate when heated. Samples should not be taken from leaking faucets, since
the surface may be contaminated from flowing over the outside of the soiled surface of