Environmental Engineering Reference
In-Depth Information
The following groups of enteric viruses have been implicated or suspected to be
transmitted by contaminated water: enteroviruses (including polioviruses and four
subsets of enterovirus [A, B, C, D]), coxsackievirus A viruses, parechoviruses
[1-3], hepatitis A (HAV) virus, hepatitis E (HEV) virus, caliciviruses (Noroviruses
and Sapoviruses), rotaviruses, adenoviruses, and astroviruses.
Algae are chlorophyllous microorganisms ranging from microscopic unicellu-
lar to “seaweed”-size multicellular forms. Their oxygenic capability in performing
the light reaction in photosynthesis is the major source of atmospheric oxy-
gen. Various types of algae serve as sources of food and pharmaceutical agents.
Although pathogenic algae are relatively rare, certain of the marine dinoflagel-
lates (e.g.,
Gonyaulax
spp.) are producers of saxitoxin and gonyautoxin, two of
the most virulent nonprotein neurotoxins of record.
Gambierdiscus toxicus
is a
tropical marine, benthic dinoflagellate, that synthesizes ciguatoxin, a polycyclic
ether compound that creates imbalance in sodium concentration in the axons and
nerve terminals causing influx of water and swelling. Ciguatera is a foodborne
illness in humans caused by eating marine species that have accumulated cells
of G. toxicus by ingestion.
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Protozoa are aerobic or anaerobic protists having a true nucleus (eukaryotic).
They reproduce usually by fission. They are classically described as simple,
unicellular microorganisms, some of which feed on particulate organic matter,
including bacteria, and others that utilize soluble organic matter. Motility may
be by protoplasmic streaming (amoeba), flagellation, or the synchronize thrash-
ing of cilia. Free-living forms may utilize soluble nutrients or ingest particulate
matter (e.g., bacteria). Several pathogenic forms exist such as
Giardia
sp. and
Cryptosporidium
sp. species, that are responsible for waterborne, communicable
diseases. Protozoa range in size from approximately 5 to 100
µ
m in size. Giardia
cysts are 8 to 18
µ
minlengthand5to12
µ
m in width and Cryptosporidium 3
to 5
m in size.
Fungi are principally aerobic, achlorophyllous microorganisms represented by
single and multicellular forms. Most notable of the multicellular fungi are the
filamentous varieties known as molds. Filaments (hyphae) are typically on the
order of 5 to 10
µ
µ
m in diameter and many millimeters in length. Molds are
important as degraders of complex animal and vegetative matter in nature but
become a nuisance in food spoilage and as producers of allergens via sporulation.
Many fungi cause diseases in both plants and animals. Certain of the higher fungi,
notably the edible mushrooms, are important foodstuffs, as are the yeasts used in
bread making and the brewing of alcoholic beverages. Some of the most valuable
antibiotics used for medical therapy are synthesized by fungi.
Helminths include intestinal worms and wormlike parasites: the roundworms
(nematodes), tapeworms (cestodes), and flatworms or flukes (trematodes). The
eggs are about 40
µ
morlargerinsize.
Poisonous plants contain toxic substances that may cause illness or even death
when consumed by humans or other animals. Poisonous animals include fish
whose flesh is poisonous when eaten in a fresh and sometimes cooked state.
(Poisonous flesh is not to be confused with decomposed food.) Acute toxins,
