Microbiological Drinking Water Parameters - The Drinking Water - page 114

or Cryptosporidium were detected in 97% of the raw water samples. After
evaluating their data, the researchers came to the conclusion that the Surface
Water Treatment Rule may have to be upgraded (subsequently, it has been)
to require additional treatment (Spellman, 2007).
DID YoU KNoW?
Some species of protozoa are part of the normal microbial flora of
animals and live in the guts of insects and mammals, helping to
break down complex food particles into simpler molecules. A small
number of species cause disease in people, including Plasmodium
vivax , which causes malaria.
Giardia
Giardia lamblia (also known as hiker's or traveler's scourge or disease) is a
microscopic parasite that can infect warm-blooded animals and humans.
Although Giardia was discovered in the 19th century, not until 1981 did the
World Health Organization (WHO) classify Giardia as a pathogen. An outer
shell called a cyst allows Giardia to survive outside the body for long peri-
ods of time. If viable cysts are ingested, Giardia can cause the illness known
as giardiasis , an intestinal illness that can cause nausea, anorexia, fever, and
severe diarrhea. The symptoms last only for several days, and the body can
naturally rid itself of the parasite in 1 to 2 months; however, for individuals
with weakened immune systems, the body often cannot rid itself of the para-
site without medical treatment.
In the United States, Giardia is the most commonly identified pathogen in
waterborne disease outbreaks. Contamination of a water supply by Giardia can
occur in two ways: (1) by the activity of animals in the watershed area of the
water supply, or (2) by the introduction of sewage into the water supply. Wild
and domestic animals are major contributors to the contamination of water
supplies. Studies have shown that, unlike many other pathogens, Giardia is not
host specific. In short, Giardia cysts excreted by animals can infect and cause
illness in humans. Additionally, in several major outbreaks of waterborne dis-
eases, the Giardia cyst source was sewage-contaminated water supplies.
Waterborne Giardia , however, can be effectively controlled by treating the
water supply. Chlorine and ozone are examples of two disinfectants known
to effectively kill Giardia cysts. Filtration of the water can also effectively trap
and remove the parasite from the water supply. The combination of disin-
fection and filtration is the most effective water treatment process available
today for prevention of Giardia contamination.
In drinking water, Giardia is regulated under the Surface Water Treatment
Rule. Although the SWTR does not establish a maximum contaminant level
(MCL) for Giardia , it does specify treatment requirements to achieve at least