Water Treatment Process
To ensure that your drinking water is always
safe, a process is used to treat millions of gallons
of raw water that arrive daily at the two water
treatment facilities serving Mesa.
The City and its water treatment plants must meet
rigorous standards established by the Environmental
Protection Agency and the Arizona Department of
Environmental Quality (ADEQ), and must be free of
coliform bacteria.
The CAP Water Treatment Plant (CAP WTP) is capable
of processing 72 million gallons per day, and the
facility is operated by ADEQ-certified operators. The raw water
for the CAPWTP comes from the Central Arizona Project.
The City also gets a portion of its drinking water
from the Val Vista Water Treatment Plant, which is
owned jointly by the cities of Phoenix and Mesa. Salt River Project
supplies the raw water to Val Vista.
The raw water is
processed according to the following steps:
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Taste and Odor
Removal |
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Taste and odors occur in the water in
the late summer or fall. Naturally occurring
organic matter decomposes in the raw water
source, and causes taste and odors. Carbon or
potassium permanganate is added to the water
to remove or reduce unpleasant taste and
odor.
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Disinfection |
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As the water enters the treatment plant,
chlorine dioxide is added for disinfection. Disinfection destroys bacteria and viruses. Chlorine is added to the water as it leaves
the treatment plant to insure that the water
that enters your home is safe to drink.
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Flocculation |
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 Aluminum
sulfate (alum) is mixed into the water. The
alum causes small impurities to stick
together and form "floc".
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Sedimentation |
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 The
floc settles to the bottom of the basin, and
is removed. Chlorine is also added during
this process for further disinfection.
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Filtration |
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 Water
flows through filters that are made of
layers of sand and coal. These filters
remove the fine particles that did not
settle out during sedimentation. |
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Final backwash
|
|
 To
remove particles from the filters, the
filters are backwashed to remove sediment
every 60 - 72 hours. Approximately 200,000
gallons of water is used to backwash a
filter. This water is then recycled back into the
raw water supply.
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Fluoridation
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The raw water has naturally occurring
fluoride, however, the Center for Disease
Control (CDC) recommends an optimum fluoride
level. This requires the city to add
supplement fluoride.
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Storage |
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 Water
is stored in reservoirs throughout the City. The distribution system brings the water to
consumers. |
Kids, look at how a Treatment Plant works:
http://www.epa.gov/safewater/kids/watertreatmentplant/index.html For more information, or for questions concerning
water treatment: Ted Bailey, Operations
Supervisor, CAP WTP
480-644-5607
ted.bailey@cityofmesa.org |
