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
...
pilot
...
plant
...
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
...
tank
...
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
...
AguaClara
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team
...
has
...
constructed.
...
As
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with
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other
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AguaClara
...
designs,
...
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
...
head
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in
...
the
...
flocculator
...
tank
...
and
...
will
...
not
...
require
...
electricity.
...
There
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are
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several
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design
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restraints
...
due
...
to
...
the
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current
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set
...
up
...
at
...
the
...
pilot
...
plant.
...
There
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was
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33.25"
...
of
...
available
...
water
...
head
...
at
...
the
...
end
...
of
...
the
...
flocculator
...
to
...
power
...
the
...
flocculator.
...
The
...
piping
...
connection
...
between
...
the
...
flocculator
...
tank
...
and
...
sedimentation
...
tank
...
also
...
cannot
...
have
...
a
...
shear
...
value
...
that
...
exceeds
...
the
...
shear
...
in
...
the
...
last
...
baffle
...
section
...
(
...
G
...
cell =
...
24
...
/s),
...
or
...
else
...
the
...
flocs
...
made
...
in
...
the
...
last
...
section
...
will
...
be
...
broken
...
up
...
upon
...
entrance
...
to
...
the
...
sedimentation
...
tank.
...
The
...
design
...
goal
...
was
...
to
...
have
...
enough
...
area
...
in
...
the
...
tank
...
to
...
create
...
a
...
floc
...
blanket
...
and
...
an
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upward
...
velocity
...
of
...
100m/day.
...
100m/day
...
is
...
the
...
upward
...
velocity
...
of
...
full
...
scale
...
plants
...
in
...
Honduras,
...
keeping
...
this
...
parameter
...
the
...
same
...
made
...
the
...
two
...
designs
...
comparable.
...
This
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low
...
flow
...
and
...
smaller
...
tank
...
set-up
...
allowed
...
for
...
parallel
...
testing
...
of
...
tanks
...
containing
...
different
...
sedimentation
...
processes.
...
Below
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is
...
a
...
table
...
of
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the
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calculated
...
pipe
...
dimensions
...
and
...
other
...
calculated
...
design
...
parameters.
...
The
...
method
...
behind
...
each
...
number
...
can
...
be
...
found
...
in
...
the
...
following
...
design.
Given Variables:
- Length (L) = 58.7 cm (23.125")
- Width (W) = 58.7 cm (23.125")
- Height (H) = 91.4 cm (36")
- Water Level (WL) = 84.5 cm (33.25")
- Flow Rate (Q) = 24 L/min
Parameters | Value |
|---|---|
Inlet Pipe | 10.16cm (4") |
Launder |
|
Launder Diameter | 3.81cm (1.5") |
Launder Height | 5 cm below sed tank WL |
Number of Holes | 15 |
Hole Diameter | 0.7541cm (19/64") |
Tank Drainage |
|
Tank Drain Diameter | 1.905cm (0.75") |
Number of Holes | 15 |
Hole Diameter | 0.3572cm (9/64") |
Hopper |
|
Hopper Removal Diameter | 1.27cm (0.5") |
Hopper Removal Line Length | 2m |
Plant Leveling Tank |
|
Leveling Tank Outlet Pipe Diameter | 7.62cm (3") |
Orfice Size | 2.223cm (7/8") |
Factor of Safety for Head Loss | 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") inches. The total number of orifices was determined to be 15. Calculations can be found here.
Orifice Diameter
The Orfice diameter was chosen to be (0.7541cm or 19/64"). Calculations shown here.
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