Coliform Bacteriaand Drinking Water
water systems must deliver safe and reliable drinking water to their customers
24 hours a day, 365 days a year. If
the water supply becomes contaminated, consumers can get seriously ill. Fortunately, public water systems take many steps to
make sure drinking water is safe. One of the
most important steps is regular testing for coliform bacteria.
What are coliform bacteria?
bacteria are present in the environment and feces of all warm-blooded animals
and humans. Coliform
bacteria are unlikely to cause illness. However, their presence in drinking
water indicates that
disease-causing organisms (pathogens) could be in the water system. Most
pathogens that can contaminate
water supplies come from the feces of humans or animals. Testing drinking water for all possible pathogens is complex,
time-consuming, and expensive. It is easy and inexpensive to test for coliform bacteria. If testing
detects coliform bacteria in a water sample,
water systems search for the source of contamination and restore safe drinking wate
There are three groups of coliform bacteria. Each is an indicator of drinking water quality and each has a different level of risk
Total coliform is a large collection of different kinds of bacteria. Fecal coliform are types of total coliform that exist in feces. E. coli is a subgroup of fecal coliform. Labs test drinking water samples for total coliform. If total coliform is present, the lab also tests the sample for E. coli.
Total coliform bacteria are common in the environment
(soil or vegetation) and are generally harmless. If a lab detects only total coliform bacteria in drinking water, the source is probably environmental and fecal contamination
is unlikely. However, if environmental contamination can enter the system, pathogens could get in too. It is important to find and resolve the source of the contamination.
Fecal coliform bacteria are a subgroup of total
coliform bacteria. They exist in the intestines
and feces of people and animals.
E. coli is
a subgroup of the fecal coliform group. Most E. coli bacteria are
harmless and exist in the intestines
of people and warm-blooded animals. However, some strains can cause illness.
The presence of E. coli in
a drinking water sample usually indicates recent fecal contamination. That
means there is a greater risk that pathogens are present.
E. coli outbreaks receive a lot of media coverage. A specific strain of E.
coli bacteria known as E.
coli O157:H7 causes most of those outbreaks. When a drinking water
sample is reported as “E.
coli present,” it does not mean that O157:H7 is present.
However, it does indicate recent fecal
contamination. Boiling or disinfecting contaminated drinking water destroys all forms of E. coli, including O157:H7.
What if coliform bacteria are found in my water?
coliform bacteria are found, water systems investigate to find out how the
contamination got into
the water. They collect additional water samples and often inspect the entire
system. Collecting additional
samples helps determine whether an actual problem exists. If the lab detects
bacteria in any of the additional samples, the initial findings are “confirmed.”
What if total coliform bacteria are confirmed in my water?
If a lab confirms total coliform bacteria in your drinking water, your water system must conduct an assessment to find out how the contamination got into the water. If the assessment identifies the cause of the contamination, the water system can usually correct the problem with repairs, treatment, or improved operation and maintenance practices. We help water systems resolve problems. When a lab confirms total coliform bacteria in drinking water, we recommend that the water system notify its customers as soon as possible. The notice will explain what the system is doing to correct the problem, when the problem will likely be resolved, and what customers may need to do until then.
What if E. coli are confirmed in my water?
Confirmation of E. coli in a water system indicates recent fecal contamination, which may pose an immediate health risk to anyone who consumes the water. The water system will issue a “health advisory” within 24 hours to alert all water users of a health risk associated with the water supply.The advisory usually recommends using boiled or bottled water for drinking, preparing food, and brushing teeth. It also outlines the steps underway to correct the problem and explains when the system expects to resolve the problem.
to health emergencies is our highest priority. We will inspect the system as
soon as possible to help the
water system resolve the problem. More water samples will be collected to find and eliminate potential contamination sources, and
a system not normally disinfected will
most likely be chlorinated and flushed. The health advisory will remain in effect until the situation is resolved and the water is safe to drink.
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