Coliform Group Bacteria
What are Coliform Group Bacteria?
Coliforms consist of a related group of bacteria species (see table below)

Where are they found?
Two Distinct Sources:
Human and Animal waste (fecal in origin)- septic systems, sewage, animal yards, etc.
Within the environment ("vegetative")- soil, vegetation, sediment, insects etc.

Why test for Coliforms?
Coliforms are "indicator" organisms associated with bacteriologically polluted water.
Their presence in finished water is indicative of contamination & is not tolerated.
Extensively studied - their presence may be associated with disease causing organisms.
Coliform testing does not indicate the presence of specific chemical contaminants
such as pesticides, metals, solvents, gasoline, nitrates, etc.

Differentiating Coliform Group Bacteria
Total Coliform Test-theoretically indicates the presence of all coliform group
bacteria, both vegetative and fecal in origin
E. coli - a coliform species found in the intestinal tract of warm-blooded animals.
- its presence can be indicative of fresh pollution from human or animal waste
- though normally benign, some E. coli strains may be deadly (0157:H7)
Fecal Coliform-those that ferment lactose & produce gas at 44.5 +/-0.20C within 24
+/- 2 hours

Consist of various genera and species of coliforms that are specifically associated
with human or animal waste.
- includes E. coli as well as others
- Fecal Coliform testing can help pinpoint the source of pollution in an aquifer
or watershed and is used to monitor the disinfection of sanitary waste water before discharge.

Coliform Group Bacteria:
Total Coliforms:
Escherichia, Enterobacter, Klebsiella, Citrobacter
Fecal Coliforms:
Escherichia, Klebsiella, Citrobacter (60% to 90% of total coliforms are fecal coliforms) 90%+ of fecal coliforms are Escherichia (usually E. coli)

Adapted From:
1. American Public Health Association. Standard Methods for the Examination of
Water and Wastewater, 18th Edition, 1992. Table 9225:I, p. 9-66.

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