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| Perchlorate
Sites |
| Olin
Corporation Facility:
425
Tennant Avenue, Morgan Hill, CA 95037 |
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| Water
Board Staff Reports |
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Review
the Water Board staff
reports which include important milestones
for the perchlorate sites in the Central Coast
Region, Region 3. |
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| Background
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| Perchlorate
is both a naturally occurring and man-made chemical,
although it is rarely found naturally in the United
States. One-third of all perchlorate used in the
United States is used in California and 90% of
California's perchlorate use is related to the
aerospace industry. There are three major sources
of perchlorate in the United States: ammonium
perchlorate has been and continues to be used
as an oxidizer in solid rocket propellant, sodium
perchlorate is used in slurry explosives, and
potassium perchlorate is used in road flares and
air bag inflation systems. Wastes from the manufacture
and improper disposal of perchlorate-containing
chemicals are increasingly being discovered in
soil and water. |
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| Health
Effects |
| Perchlorate
is known to interfere with the natural function
of the thyroid gland by inhibiting the uptake of
iodide. Because iodide is an essential component
of thyroid hormones, perchlorate disrupts how the
thyroid functions. Such an effect decreases production
of thyroid hormones, which are needed for prenatal
and postnatal growth and development, as well as
for normal body metabolism. Potassium perchlorate
was used until recently to treat hyperthyroidism
related to Grave's disease, and is still used diagnostically
to test thyroid hormone production in some clinical
settings. |
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| Treatment
Methods |
Treatment
of perchlorate contamination in water is complicated
because the perchlorate anion does not respond
to typical water treatment techniques due to its
fundamental physical and chemical nature. The
perchlorate tetrahedron itself is structured such
that the four oxygen atoms surround the central
chlorine atom, effectively blocking reductants
from directly attacking the chlorine. Although
perchlorate is thermodynamically a strong oxidizing
agent, it is a kinetically sluggish species, making
its reduction generally very slow and rendering
common reductants ineffective. It can persist
in the environment for many decades under typical
groundwater and surface water conditions because
of its resistance to react with other available
constituents.
Perchlorate
treatment technologies may be generally classified
into categories of destruction or removal technologies.
Destructive processes include biological reduction,
chemical reduction, and electrochemical reduction.
Physical removal processes include anion exchange,
membrane filtration (including reverse osmosis and
nanofiltration), and electrodialysis, which all
require subsequent disposal of removed perchlorate.
The optimum treatment technology for a given perchlorate
occurrence may depend on several factors, including
perchlorate concentration, the presence and concentration
of co-contaminants, other water quality parameters
and geochemical parameters. The presence of indigenous
perchlorate-reducing microbes and substances inhibitory
to their activity will also influence perchlorate
treatment technology effectiveness. For in-situ
treatment of perchlorate contamination, variables
related to the site hydrogeologic setting, such
as depth to and distribution of contaminants, soil
permeability, groundwater flow velocity, etc. are
also additionally important. |
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