Chemical Doser Design
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h1. Chemical Doser Design {float:right|border=2px solid black|width=260px} [!Laboratory Research Set-ups^Labeled Robust ACD freestanding F08 2.JPG|width=260px!|Laboratory Research Set-ups] {float} |
The
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chemical
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doser
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(CD)
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has
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three
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principle
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components:
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a
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float,
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a
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lever
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arm,
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and
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a
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...
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(FC).
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The
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float
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currently
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used
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in
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the
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lab
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for
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data
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collection
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is
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a
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45.5
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cm
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long
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4
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in
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PVC
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tube
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capped
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at
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both
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ends
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and
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partially
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filled
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with
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sand
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so
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that
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it
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weighs
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8
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lbs.
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It
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rests
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33.5
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cm
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below
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and
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12
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cm
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above
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the
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water
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line
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in
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a
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virtual
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grit
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chamber,
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which
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is
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a
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deep
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bucket
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with
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a
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pressure
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sensor
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at
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its
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base.
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This
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pressure
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sensor
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provides
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readings
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of
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the
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water
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level
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in
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the
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bucket.
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The
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float
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is
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connected
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via
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low-elasticity
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fishing
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line
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to
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the
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lever
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arm.
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The
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lever
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arm
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is
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a
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68
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cm
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length
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of
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1
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1/4
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in
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schedule
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40
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PVC
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pipe
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with
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a
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pivot
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point
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at
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34
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cm
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(the
...
center).
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Opposite
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of
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the
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pivot
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there
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are
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notches
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cut
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into
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the
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pipe
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at
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5
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cm
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length
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intervals.
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The
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chemical
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doser
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hangs
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from
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these
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notches.
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A
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1
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1/2
...
in
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schedule
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40
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PVC
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pipe
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attached
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to
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a
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flange
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base
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holds
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up
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the
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lever
...
arm.
...
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The
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top
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of
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the
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pipe
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is
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cut
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in
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a
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saddle
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shape
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to
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fit
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the
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lever
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arm
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through
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it
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and
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create
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the
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pivot.
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The
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height
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of
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this
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base
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pipe
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depends
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on
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the
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design
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constraints
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of
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the
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plant
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it
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will
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be
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built
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for.
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The
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FC
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should
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be
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attached
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to
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the
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base
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pipe
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with
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two
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clamps
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that
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are
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interconnected
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so
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that
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they
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firmly
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anchor
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the
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FC
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at
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the
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appropriate
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height
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for
...
...
...
...
.
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Only
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one
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clamp
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was
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used
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during
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experimental
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testing
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because
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the
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FC
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was
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being
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continually
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checked
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and
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re-zeroed,
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and
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it
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was
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being
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used
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in
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a
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very
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controlled
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environment.
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Additional
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clamps
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would
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be
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necessary
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for
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robust
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plant
...
operation.
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The
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chemical
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dosing
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tube
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is
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a
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tube
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with
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an
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open
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T
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connection
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at
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the
...
top,
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which
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allows
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the
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FC
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outflow
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tubing
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to
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drain
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through
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a
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pressure
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break
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T.
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The
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tubing
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exiting
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the
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pressure
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break
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T
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has
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a
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larger
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diameter
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than
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the
...
tubing
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entering
...
it.
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The
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pressure
...
break
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and
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larger
...
outflow
...
tubing
...
allow
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a
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free
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surface at the same height as the discharge to the rapid mix (minus head loss) to form inside the larger tube while air can also flow through the tube. Currently ¼ inch outer diameter tubing is used to connect the flow controller to the pressure break T, but it is not known what size tubing is necessary to allow air to flow after the T. Experience has indicated that ½ inch outer diameter tubing is large enough, but it is possible that tubing with an outer diameter as small as 3/8 inch could work as well. The larger tube is then connected to 1/4 in outer diameter tubing, which connects the CD to the rapid mix. It is unclear if this final connection is needed, though, and it may be removed so that the larger tubing connects the T to the rapid mix directly.
For laboratory testing, water flows from the bottom of the chemical dosing tube to a plastic column with a pressure sensor at the bottom. This pressure sensor gives readings of water height in the column, which can be converted into flow rates from the FC.