LaMotte MF 3-0035 - Manual (Page 9)

Cryptosporidium) that live in the gastrointestinal tract and are shed into the water
through the waste (feces) of warm-blooded animals. However, analyzing for all
possible pathogens is impractical. It is difficult, time consuming, and expensive. The
EPA recommends using indicator organisms, such as fecal bacteria, as indirect
evidence of the possible presence of pathogens in water. 2 The two most important
fecal bacteria indicators are E. coli and Enterococcus. We will discuss the use of E.
coli as it relates to the USEPA standards for water pollution. 2
Escherichia coli (E. coli) is the United States Environmental Protection Agency’s
(USEPA) most commonly recommended indicator of fecal contamination in fresh
waters. It is present in high numbers in the gastrointestinal tracts of warm-blooded
animals (humans, dogs, bears, cows, ducks, geese) and therefore provides a sensitive
measure of fecal pollution. Researchers have found that its presence in water is often
associated with water borne illness outbreaks actually caused by the other pathogens
mentioned above. E. coli do not live long in water so that their presence indicates a
fairly recent contamination event (up to 48 hours).
The current EPA water quality standard for E. coli relates to approximately 8
gastrointestinal illnesses per 1,000 swimmers. This is considered an acceptable level
of disease for people who come in contact with the tested water. If the indicator counts
are measured above the standard acceptable level, then the risk of becoming infected
from that water source is unacceptably high. In the past fecal coliforms were used as
the indicator for water standards with maximum allowable counts of 200 FC(fecal
coliforms) per 100 mL.
2
Coliform bacteria are members of the family Enterobacteriaceae, which are gram
negative, non-spore forming rods that ferment the sugar lactose to produce gas and
acid. E. coli is a genus (Escherichia) and species (coli) in the total coliform group. It is
also a fecal coliform (FC), a smaller subset of total coliforms. Fecal coliforms are
defined as coliforms that can grow at 44.5°C, which is too hot for most of the other
coliforms. Fecal coliforms live in the gastrointestinal tract of warm-blooded animals,
such as dogs, cats, birds, mammals, and people. E. coli belongs to both groups of
bacteria that are reported in water quality studies; E. coli is a fecal coliform (FC) and a
total coliform (TC).
3
New guidelines from the USEPA recommend E. coli or Fecal Coliform standards that
vary with the potential human exposure to the water. For example, during summer on
a lake which allows swimming and water skiing, the standards will be stricter than
during the winter on that same lake or if it was a rarely used swimming area. Each
state works with the EPA to determine the best standards that apply to their water
bodies. Refer to the EPA document, “Bacterial Water Quality Standards for
Recreational Waters (Freshwater and Marine Waters)-Status Report” at this website:
www.epa.gov/waterscience/beaches/local/statreptac.pdf for more specific
standards from your state. 2
Normal testing for E. coli cannot determine the source of the contamination (e.g.
animal vs. human), since it is present in all warm-blooded mammals. Drinking water
is often drawn from rivers, lakes, streams, and other reservoirs open to non-point
source or point source pollution. Water company scientists measure fecal coliform
bacteria, in addition to dissolved oxygen, pH, temperature, and turbidity to determine
water quality. High levels of fecal coliform or E. coli have caused closures of shellfish
beds, beaches, and other recreational water sources. Point source pollution may be
caused by septic systems, municipal sewage discharges, animal feed operations,
farms, and boaters discharging wastes. Non-point source pollution from E. coli may
be related to runoff of fecal waste from the land after a heavy rainfall. For example, in
urban areas, E. coli runoff occurs from runoff of pet feces in the park or on the street
into creeks, rivers, streams, lakes, or groundwater. E. coli levels in urban storm water
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