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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. 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:
The raw water is injected with a polyaluminum
chloride called S5 at the pump house for added contact time. Just before
the raw water enters the filter units it is injected with a cationic
polymer called 1160P. The polymer has a positive charge on it and makes the
particles in the water stick to it. 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 1.2-4.0 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 are 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 5.9
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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email.
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