Environmental Engineering Reference
In-Depth Information
Perchlorate is a stable molecule of one chlorine and four oxygen atoms that has been
recognized as a health-threatening contaminant in surface water, groundwater, and soil.
In March 1998, the US Environmental Protection Agency's (USEPA) Ofice of Water added
perchlorate to the drinking water contaminant candidate list. Perchlorate ions originate
as a contaminant in ground water and surface waters from the dissolution of perchlo-
rate salts. Approximately 90% of all perchlorate salts are manufactured as ammonium
perchlorate that is used as an energetic booster of solid oxidants in rockets and missiles.
Ammonium perchlorate has limited shelf life, requiring periodic replacement of rocket
and missile fuels. Therefore, since the 1950s, large quantities have been removed from
solid rocket boosters and missiles and subsequently disposed of in Nevada, California,
Utah, and other states where rockets and missiles are produced (Damian and Pontius,
1990), causing severe water contamination of perchlorate in these areas. Other uses of
perchlorate compounds include pyrotechnics, matches, munitions, the chemical analytics
industry, fertilizer, additives in lubricating oils, tanning, inished leather, fabric ixer, dye,
electroplating, aluminum reining, rubber manufacture, paint and enamel production, as
an additive in cattle feed, magnesium batteries, and as a component of automobile air
bag inlators (Damian and Pontius, 1990; USEPA, 1993; Tarver et al., 1996; American Water
Works Association Research Foundation [AWWARF], 1997; Urbansky, 1998; Renner, 1999;
USEPA, 1998). Because of the high solubility of most perchlorate salts, the resulting per-
chlorate ion is extremely mobile in aqueous systems.
Although perchlorate salts are highly reactive as solids, once dissolved in water and
under natural conditions, the perchlorate anion becomes relatively nonreactive and sta-
ble. The wide use of perchlorate and its high mobility in aqueous systems has caused
widespread groundwater contamination of perchlorate in hundreds of locations in at least
43 states, potentially affecting the health of more than 20 million people that reside in
these contaminated areas. Perchlorate contamination is of particular concern because of
the persistent and toxic nature of this compound and because its stable physical and chem-
ical properties make it challenging to treat.
Perchlorate-induced health problems are most commonly observed by their impact on
or through the thyroid gland in the form of a decrease in thyroid hormone output. The
thyroid gland takes up iodide ions from the bloodstream and uses the iodide to regulate
metabolism along with other functions. However, in iodide uptake, the presence of ions
larger than iodide, such as perchlorate, can reduce thyroid hormone production and thus
disrupt metabolism. Although this property of perchlorate makes it useful as a medical
treatment for Graves' disease (hyperthyroidism), it also creates a perchlorate health con-
cern (Urbansky, 1998; EPA National Center for Environmental Assessment, 2004). Primary
pathways for exposure to perchlorate in humans include ingestion of contaminated drink-
ing water and food crops. The National Research Council reported that daily ingestion of
up to 0.0007 mg of perchlorate per kilogram of body weight can occur without adversely
affecting the health of the most sensitive populations.
32.2 Perchlorate Removal Technologies
Supported by the US government, several treatment technologies have been examined
for perchlorate removal in contaminated water. Technologies examined for removal of
