Environmental Engineering Reference
In-Depth Information
TAble 6.1
Simplified Classification of Microorganisms
Cell
Classification
Kingdom
Members
Animal
Rotifers
Crustaceans
Worms and larvae
Plant
Ferns
Eucaryotic
Mosses
Protista
Protozoa
Algae
Fungi
Bacteria
Procaryotic
Lower algae forms
To provide the fundamental knowledge of microbiology that the drinking
water practitioner requires, in this chapter we pursue a basic but far-reaching
structured approach. To ensure currency, we include a lengthy and informa-
tive discussion of waterborne protozoans such as
Giardia
,
Cryptosporidium
,
and others, all of which have received recent media attention.
Waterborne Diseases
Average citizens living in the United States or Europe have heard of water-
borne disease-causing microorganisms, but in this modern age most
people don't give them a second thought, even though the World Health
Organization (WHO) estimates that waterborne diseases account for 5 mil-
lion deaths annually, worldwide. All the news about waterborne disease is
not necessarily grim, however. Modern sanitation practices have made con-
tracting most of the waterborne diseases (see
Table 6.2
) rare in the United
States and Europe. It would be foolhardy and deadly for us to forget, how-
ever, that in other areas of the world disease-causing organisms are still
in the environment—especially that part of the environment that is water
(Spellman, 1997). The bottom line is that waterborne diseases have not been
eliminated by treatment, or by this century's much improved sanitary condi-
tions, not even in the industrialized parts of the world.
When we refer to
waterborne disease
, the uninitiated may get the wrong
impression about water and waterborne disease. In the water environment,
water is not a medium for the
growth
of pathogenic microorganisms, but
instead is a means of
transmission
or conveyance (a conduit—hence, use of
