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Sedimentation Tank Design
Introduction
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h1. Sedimentation Tank Design h3. Introduction {float:right|border=2px solid black|width=200px} {anchor:plant leveling tank connection}[!Sed_Tanks.JPG|width=200px!|Sed_Tanks.JPG] h5.Front View of the Floc Blanket Sedimentation Tank {float} |
The
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pilot
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plant
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sedimentation
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tank
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is
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a
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vertical
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flow
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style
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tank
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and
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uses
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only
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a
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floc
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blanket
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as
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its
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removal
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mechanism.
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This
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tank
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was
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the
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first
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close
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to
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full
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scale
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sludge
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blanket
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sedimentation
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tank
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that
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the
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AguaClara
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team
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has
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constructed.
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As
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with
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other
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AguaClara
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designs,
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the
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tank
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will
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be
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run
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by
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the
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elevation
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head
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in
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the
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flocculator
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tank
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and
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will
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not
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require
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electricity.
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There
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are
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several
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design
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restraints
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due
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to
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the
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current
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set
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up
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at
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the
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pilot
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plant.
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There
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was
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33.25"
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of
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available
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water
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head
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at
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the
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end
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of
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the
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flocculator
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to
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power
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the
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flocculator.
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The
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piping
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connection
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between
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the
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flocculator
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tank
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and
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sedimentation
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tank
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also
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cannot
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have
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a
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shear
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value
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that
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exceeds
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the
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shear
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in
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the
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last
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baffle
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section
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(
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G
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cell =
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24
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/s),
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or
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else
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the
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flocs
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made
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in
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the
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last
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section
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will
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be
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broken
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up
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upon
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entrance
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to
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the
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sedimentation
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tank.
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The
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design
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goal
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was
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to
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have
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enough
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area
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in
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the
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tank
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to
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create
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a
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floc
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blanket
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and
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an
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upward
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velocity
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of
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100m/day.
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100m/day
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is
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the
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upward
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velocity
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of
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full
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scale
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plants
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in
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Honduras,
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keeping
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this
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parameter
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the
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same
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made
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the
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two
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designs
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comparable.
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This
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low
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flow
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and
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smaller
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tank
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set-up
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allowed
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for
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parallel
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testing
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of
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tanks
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containing
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different
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sedimentation
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processes.
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Below
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is
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a
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table
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of
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the
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calculated
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pipe
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dimensions
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and
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other
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calculated
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design
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parameters.
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The
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method
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behind
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each
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number
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can
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be
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found
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in
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the
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following
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design.
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Given
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Variables:
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- Length
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- (L)
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- =
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- 58.7
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- cm
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- (23.125")
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- Width
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- (W)
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- =
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- 58.7
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- cm
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- (23.125")
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- Height
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- (H)
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- =
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- 91.4
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- cm
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- (36")
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- Water
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- Level
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- (WL)
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- =
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- 84.5
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- cm
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- (33.25")
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- Flow
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- Rate
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- (Q)
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- =
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- 24
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- L/min
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Parameters | Value |
|---|---|
Inlet Pipe | 10.16cm |
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(4") |
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Launder |
|
|---|---|
Launder Diameter | 3.81cm |
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(1.5") |
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Launder |
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Height |
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5 |
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cm |
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below |
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sed |
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tank |
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WL |
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Number |
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of |
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Holes |
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15 | |
Hole Diameter | 0.7541cm |
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(19/64") |
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Tank Drainage |
|
|---|---|
Tank Drain Diameter | 1.905cm |
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(0.75") |
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Number |
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of |
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Holes |
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15 | |
Hole Diameter | 0.3572cm |
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(9/64") |
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Hopper |
|
|---|---|
Hopper Removal Diameter | 1.27cm |
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(0.5") |
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Hopper |
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Removal |
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Line |
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Length |
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2m | |
Plant Leveling Tank |
|
|---|---|
Leveling Tank Outlet Pipe Diameter | 7.62cm (3") |
Orfice Size | 2.223cm (7/8") |
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Factor |
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of |
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Safety |
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for |
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Head |
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Loss |
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18 |
Upward Velocity:
From the reasoning shown here, the flow rate was determined to be 24 L/min.
Inlet Pipe Calculations:
Through the calculations found here, the inlet pipe was determined to be 4" in diameter.
Launder Calculations:
Pipe Diameter
The effluent launder will span the length of the tank about 10.16cm (4") off of the center of the tank. The launder is placed 5.08cm (2") beneath the water level. The best pipe diameter is 3.81cm (1.5")
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inches.
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The
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total
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number
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of
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orifices
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was
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determined
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to
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be
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15.
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Calculations
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can
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be
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found
...
...
.
Orifice Diameter
The Orfice diameter was chosen to be (0.7541cm
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or
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19/64").
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Calculations
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shown
...
...
.
Orifice Head Loss
The minor loss for an orifice was calculated to be 4.54 cm. Calulations are shown here.
Secondary Outlet from the Flocculator
The flow rate of the sedimentation tank is designed to be 24 L/min, but the flocculator flow rate is designed to be as high as 110 L/min. This means that excess flow needs to bypass the sedimentation tank and go directly to the existing outlet in the flocculation tank. The calculations for the solution can be found here.
Hopper Design for Floc Blanket
Given the calculated amount of sludge the tank will create, a continuous sludge drainage system was created. More details are found here.
Plant Leveling Tank
In order to ensure this the head loss out of the plant leveling tank (which controls flow in the sedimentation tank) had to be significantly greater than the head loss over the alternative exit in the flocculator. We chose a factor of safety of 18, thus the head loss out of the plant leveling tank would be 18 times the head loss out of the flocculator.More details are included here.
Tank Drainage Manifold
A tank drain system was designed to drain in 30 minutes (Q ~drain~ = 20 L/min). The manifold diameter was determined to be 1.905cm (0.75") and the orifice diameter is 0.3572cm (9/64"). The hole size in the drain manifold was increased to 1/4" to allow for faster tank drainage. Here are more details.
Lamella
Lamella Design