Science of Water : Concepts and Applications

140 The Science of Water: Concepts and Applications
of waterborne disease. In 1996, in its next series of surface water regulations, the USEPA included
Cryptosporidium.
To test the need for and the effectiveness of the USEPA’s SWTR, LeChevallier et al. conducted
a study on the occurrence and distribution of Giardia and Cryptosporidium organisms in raw water
supplies to 66 surface water fi lter plants. These plants were located in 14 states and 1 Canadian
province. A combined immunofl uorescence test indicated that cysts and oocysts were widely dispersed
in the aquatic environment. Giardia spp. was detected in more than 80% of the samples.
Cryptosporidium spp. was found in 85% of the sample locations. Taking into account several variables,
Giardia or Cryptosporidium spp. were detected in 97% of the raw water samples. After evaluating
their data, the researchers concluded that the SWTR might have to be upgraded (subsequently,
it has been) to require additional treatment (LeChevallier et al., 1991).
Giardia
Giardia (gee-ar-dee-ah) lamblia (also known as hiker’s/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, that allows it to survive outside the body for long periods,
protects Giardia. 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.
In the United States, Giardia is the most commonly identifi ed 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 in contaminating water supplies.
Studies have also shown that, unlike many other pathogens, Giardia is not host-specifi c. In short,
Giardia cysts excreted by animals can infect and cause illness in humans. Additionally, in several
major outbreaks of waterborne diseases, the Giardia cyst source was sewage-contaminated water
supplies.
Treating the water supply, however, can effectively control waterborne Giardia. 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
disinfection and fi ltration is the most effective water treatment process available today for prevention
of Giardia contamination.
In drinking water, Giardia is regulated under the SWTR. Although the SWTR does not establish
a maximum contaminant level (MCL) for Giardia, it does specify treatment requirements to
achieve at least 99.9% (3-log) removal and inactivation of Giardia. This regulation requires that all
drinking water systems using surface water or groundwater under the infl uence of surface water
must disinfect and fi lter the water. The Enhanced Surface Water Treatment Rule (ESWTR), which
includes Cryptosporidium and further regulates Giardia, was established in December 1996.
GIARDIASIS
During the past 15 years, giardiasis (CDC, 1995) has been recognized as one of the most frequently
occurring waterborne diseases in the United States. G. lamblia cysts have been discovered in the
United States in places as far apart as Estes Park, Colorado (near the Continental Divide); Missoula,
Montana; Wilkes-Barre, Scranton, and Hazleton, Pennsylvania; and Pittsfi eld and Lawrence, Massachusetts,
just to name a few.
Giardiasis is characterized by intestinal symptoms that usually last 1 week or more and may
be accompanied by one or more of the following: diarrhea, abdominal cramps, bloating, fl atulence,
fatigue, and weight loss. Although vomiting and fever are commonly listed as relatively frequent
symptoms, people involved in waterborne outbreaks in the United States have not commonly
reported them.