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Chapter 16
Pollution from Biological Sources
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Waterborne diseases in the U.S. are
rare. The greater problem is contamination of food sources by
(in order of undesirability):
1 Private package sewer plants -unmanned,
with daily spot check- often not on weekends
2. Combined sewer overflows (CSO) - storm
water & sewage overwhelm system
3. Septic tanks- also susceptible to CSO
4. Even municipal wastewater treatment
plants can cause pollution when not properly maintained
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There are 4 main types of pathogenic organisms:
1.Viruses: Less than 1/10 th
the size of a bacteria. They need a specific host.
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Human waste is primary source of all except
Reoviruses which inhabit animal waste as well as human waste.
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Groundwater probably accounts for about 1/2
of all waterborne-related illnesses as viruses & bacteria survive longer
in groundwater.
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Viruses are the predominant causes of water-related
illnesses in the U.S.
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The standard separation of a well & a
septic tank is 100 feet, but viruses move over 200 feet. Hepatitis is the
major viral water-related disease & is resistant to chlorine. It is
bioaccumulated in shellfish.
2. Bacteria:
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Also primarily from human waste, but being
larger they are easily filtered out or destroyed.
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In U.S. Salmonella types are the most common,
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Elsewhere cholera, tuberculosis, & leptospirosis
are still problems.
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Salmonella cause typhoid, but gastroenteritis,
shigellosis & salmonellosis are the main threats in the U.S.
3. Protozoa: Single-celled.
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10% of U.S. citizens estimated to have amebic
cysts, but they easy to filter out.
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An amoeba found in the warm water near power
plant cooling towers causes meningoencephalitis which can be fatal.
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Cryptosporidia infected 300,000 in Milwaukee
in 1993. Only 1 died.
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Malaria is also a protozoa & though not
waterborne, its host is -any of 50 or more species of anopheles mosquito
carry the parasite.
4. Worms
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A. Flatworms-
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Flukes-when humans not natural host penetrate
only outer skin-get swimmers itch
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Tapeworms
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B. Roundworms- about 1/2 parasitic. Some bore
through tissue & get to be 4 feet long.
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Non-indigenous species
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Gause's Principal- no two species can exist
indefinitely on a single limiting resource-
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Leibig's Law of the Minimum form the Principal
of Competitive Exclusion- two species cannot coexist in the same area if
they both need the same resource & it is limited with respect to their
ability to use it.
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This competition may occur at any life stage
& can include pollution. Examples: water hyacinth in Florida, zebra
mussel in Great Lakes, Asiatic clam, carp.
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Introduction of non-indigenous species can
be helpful, but results are hard to predict & accidental introduction
is rarely beneficial.
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