Pollution from Biological Sources
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
There are 4 main types of pathogenic organisms:
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
1.Viruses: Less than 1/10 th
the size of a bacteria. They need a specific host.
Human waste is primary source of all except
Reoviruses which inhabit animal waste as well as human waste.
Groundwater probably accounts for about 1/2
of all waterborne-related illnesses as viruses & bacteria survive longer
Viruses are the predominant causes of water-related
illnesses in the U.S.
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.
Also primarily from human waste, but being
larger they are easily filtered out or destroyed.
In U.S. Salmonella types are the most common,
Elsewhere cholera, tuberculosis, & leptospirosis
are still problems.
Salmonella cause typhoid, but gastroenteritis,
shigellosis & salmonellosis are the main threats in the U.S.
3. Protozoa: Single-celled.
10% of U.S. citizens estimated to have amebic
cysts, but they easy to filter out.
An amoeba found in the warm water near power
plant cooling towers causes meningoencephalitis which can be fatal.
Cryptosporidia infected 300,000 in Milwaukee
in 1993. Only 1 died.
Malaria is also a protozoa & though not
waterborne, its host is -any of 50 or more species of anopheles mosquito
carry the parasite.
Flukes-when humans not natural host penetrate
only outer skin-get swimmers itch
B. Roundworms- about 1/2 parasitic. Some bore
through tissue & get to be 4 feet long.
Gause's Principal- no two species can exist
indefinitely on a single limiting resource-
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.
This competition may occur at any life stage
& can include pollution. Examples: water hyacinth in Florida, zebra
mussel in Great Lakes, Asiatic clam, carp.
Introduction of non-indigenous species can
be helpful, but results are hard to predict & accidental introduction
is rarely beneficial.