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JACKMAN UTILITY DISTRICT
Water Filter Plant
Raw Water Daily Average: 80,000 gallons
Filtered Water Daily
Average: 60,000 gallons
Tri-Mite Treatment Units:
The district built the new filter plant in
1995-96. Two filter units were installed
each capable of filtering 100gpm of raw water, a combined capacity of
200gpm. Water is pumped directly
from Big Wood Lake to this building. You will notice the green pipe labeled
Raw Water. It enters the building
and is piped into the filter units.
Currently the units are set to filter 60gpm each for a combined
120gpm. Each filter unit has two
sides, an adsorption clarifier, and an anthracite filter bed. The clarifier consists of small white
plastic beads and a metal stainless steel screen. The raw water flows up through the
clarifier. The clarifier’s job is to
filter out particles from the water.
The anthracite bed consists of 2 feet of sand covered by 3.5 feet of
small black anthracite. The filter
beds job is to remove any remaining particles still suspended in the
water. The units are programmed to
clean themselves after filtering for a certain amount of time. The clarifier is set to automatically
flush. Air, followed by raw water,
is forced up through the clarifier for a certain amount of time to dislodge
anything stuck in the beads. The
filter bed is also programmed to backwash automatically. During a backwash air, followed by
filtered water, is forced up through the filter bed for the same reason of
dislodging any material stuck in the filters.
Coagulants and Polymers:
Just before the raw water enters the filter
units it is injected with a cationic polymer called 1160P and a coagulant
EC461. The polymer has a positive
charge on it and makes the particles in the water stick to it. The EC461 makes the sticky particles want
to clump together, or floc. The raw water is
pumped up through the clarifier where the sticky particles attach to the
white beads. The water then flows
down into the filter bed. We measure
the efficiency of the filter units using turbidity readings. Turbidity is a measurement of how much
stuff is floating in the water. The
raw water entering the units usually has a turbidity of about 1.2-2.0 and
the filtered water usually is about .04-.10. It is our job as operators to monitor the
filter units daily. The water goes
through cycles, as do the seasons.
Depending on temperature and raw water turbidity the chemicals
dosages of each unit needs to be adjusted.
Spring and fall are two times of the year when the units need
constant monitoring and daily adjusting.
To aid us in figuring how much chemicals are needed to properly
filter the material out of the water we use a method called a jar test. This helps us accurately determine what
dose we should be running the units at.
Sodium Hypochlorite:
Once the water filters through the filter unit
it flows into a blue pipe labeled filtered water. Sodium hypochlorite, chlorine, is added
and the water goes into the clear well.
The clear well is a 60,000 gallon maze that provides contact time,
the time needed for the chlorine to disinfect the water and make it safe
for consumption. The amount of
chlorine added to the water also changes with the seasons and water
temperature variations. The summer
months require an increased amount of chlorine because the demand in the
water is higher. There is more things living in the water that could make you
sick. Interestingly, colder water is
harder to disinfect, yet it does not have as much living in it so the
demand is lower in the winter months.
Chlorine residuals are how we check to make sure the water is safe.
A residual shows us that there is still chlorine left in the water after
its work is done to kill anything it may come across out in the system.
We are required to maintain a free residual leaving the plant of
.2ppm. This is saying there are 2
particles of chlorine for every 1,000,000 particles of water. We check the residuals in the system
daily. We are required to maintain a
trace of free chlorine residual out in the system at all times. Once the water has made it journey
through the maze of the clear well it is called finished water and is
pumped to town.
Soda Ash:
Soda Ash is added to the
finished water to increase the pH of the water as it heads to town. The raw water has a pH of about 6.2
coming from the lake which rises to about 7.2 after it travels through the
filter plant. We boost it up to
about an 8.0 leaving the plant. This
helps protect the pipes in the system from corrosion caused by acidic water
below a pH of 7.0.
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question about the Jackman Utility District, please click here to send an
email.
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