LESSON 3
BACTERIOLOGICAL TESTS AND STANDARDS
Section I. BACTERIOLOGICAL TESTS
3-1.
GENERAL
Bacteriological tests are a measure of the portability of a water supply. One of
the criteria of potabiIity (para 1-4a) is that water be free from pathogenic organisms. All
surface and ground waters can be expected to contain pathogenic organisms and must,
therefore, be disinfected prior to being used as drinking water supplies. Treated water
supplies should be free from pathogens; however, we cannot be sure of the
effectiveness of our treatment processes unless we conduct bacteriological tests for the
presence of bacteria.
3-2.
INDICATOR ORGANISMS
a. Waterborne Diseases. Pathogens that may exist in water supplies include
the causative of the waterborne diseases listed below. All of these organisms are
introduced into a water supply by contamination of the water with urine, feces, or both
from infected persons or animals.
(1)
Typhoid fever.
(2)
Paratyphoid fever.
(3)
Shigellosis (bacillary dysentery).
(4)
Cholera.
(5)
Viral Hepatitis.
(6)
Leptospirosis.
(7)
Amebiasis.
(8)
Schistosomiasis (a parasitic infestation).
b. Reasons for Using Indicator Organisms. It is possible, in some cases, to
conduct bacteriological examinations of water for the presence of specific pathogens. It
is not practical to do so, however; first, because the concentration of pathogens is
usually quite low; and second, because isolation and detection techniques for even the
most common pathogens involve relatively complicated procedures that will exceed the
capabilities of all but a few well-equipped water laboratories. Consequently, we test for
MD0160
3-2
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