...
Marcala
...
Flocculation Details
Flocculation Tank
The baffle configurations and dimensions had to be calculated to fit the existing infrastructure in Marcala. Instead of the plastic polycarbonate baffles used in the Ojojona plant, ferrous cement baffles will be used in the Marcala plant. Using polycarbonate baffles provide an advantage in the flexibility of design because the spacing's can be adjusted. Since the ferrous cement baffles will be used instead, they will be mortared to the tank. This leaves no room for adjustment in the baffles once they are constructed.
Grooves will be made on the flocculation tank walls to support the ferrous cement baffles. These grooves will need to be constructed accurately to hold the baffles correctly. Also, in order to drain the flocculation tank, drains between each two consecutive baffles are now necessary. Previously, using polycarbonate baffles, water crept through the sides of the baffles when the operator wished to drain the flocculation tank. The use of ferrous cement baffles that are mortared to the wall restricts the water from being able to drain between the baffles. As a result, a hole will need to be placed on the bottom of the baffles to allow for drainage. This hole must be sized optimally to ensure minimal short circuiting of the flow and to ensure proper draining time for the plant.
Baffle Spacing for the Marcala Plant
| Wiki Markup |
|---|
{ Details{*}{color} {cloak:id=Flocculation Tank} h4. {toggle-cloak:id=Flocculation Tank} *Flocculation Tank* {cloak:id=Flocculation Tank} The baffle configurations and dimensions had to be calculated to fit the existing infrastructure in Marcala. Instead of the plastic polycarbonate baffles used in the Ojojona plant, ferrous cement baffles will be used in the Marcala plant. Using polycarbonate baffles provide an advantage in the flexibility of design because the spacing's can be adjusted. Since the ferrous cement baffles will be used instead, they will be mortared to the tank. This leaves no room for adjustment in the baffles once they are constructed. Grooves will be made on the flocculation tank walls to support the ferrous cement baffles. These grooves will need to be constructed accurately to hold the baffles correctly. Also, in order to drain the flocculation tank, drains between each two consecutive baffles are now necessary. Previously, using polycarbonate baffles, water crept through the sides of the baffles when the operator wished to drain the flocculation tank. The use of ferrous cement baffles that are mortared to the wall restricts the water from being able to drain between the baffles. As a result, a hole will need to be placed on the bottom of the baffles to allow for drainage. This hole must be sized optimally to ensure minimal short circuiting of the flow and to ensure proper draining time for the plant. {cloak} h4. {toggle-cloak:id=Baffle Spacing for the Marcala Plant} *Baffle Spacing for the Marcala Plant* {cloak:id=Baffle Spacing for the Marcala Plant} {float:right|border=2px solid black|width=200px} {anchor:This figure}[!Marcala Plant Design^Marcala Plant Layout.jpg|width=200px!|Marcala Plant Design^Marcala Plant Layout.jpg] h5. General Layout of the Marcala Plant {float} [ |
...
...
depicts
...
a
...
general
...
top
...
view
...
of
...
the
...
layout
...
of
...
the
...
Marcala
...
plant.
...
Only
...
the
...
baffle
...
spacing
...
for
...
flocculation
...
tanks
...
C
...
and
...
D
...
were
...
calculated
...
due
...
to
...
anticipated
...
changes
...
to
...
the
...
current
...
flocculator
...
design
...
program.
...
The
...
spacing
...
in
...
tanks
...
A
...
and
...
B
...
are
...
areas
...
with
...
more
...
variation
...
in
...
potential
...
baffle
...
spacing's
...
and
...
since
...
the
...
baffles
...
are
...
not
...
removable,
...
the
...
calculations
...
will
...
be
...
delayed
...
for
...
these
...
two
...
sections.
...
Due
...
to
...
the
...
many
...
constraints
...
in
...
the
...
flocculation
...
tank
...
including
...
the
...
sloping
...
floor
...
and
...
the
...
cement
...
beams
...
under
...
which
...
it
...
was
...
preferred
...
not
...
to
...
build,
...
the
...
spacing
...
of
...
the
...
baffles
...
was
...
a
...
unique
...
challenge.
...
The
...
spacing
...
between
...
the
...
baffles
...
in
...
flocculation
...
tanks
...
C
...
and
...
D
...
was
...
calculated
...
using
...
Monroe
...
Weber-Shirk's
...
...
...
...
.
...
Important
...
care
...
must
...
ensure
...
that
...
the
...
baffles
...
are
...
the
...
correct
...
spacing
...
to
...
keep
...
the
...
flocs
...
from
...
breaking
...
apart.
...
The
...
results
...
of
...
the
...
MathCAD
...
program
...
were
...
slightly
...
modified
...
through
...
the
...
two
...
tanks
...
to
...
accommodate
...
the
...
unique
...
tanks.
...
Additionally,
...
the
...
thickness
...
of
...
the
...
ferrous
...
cement
...
baffles
...
themselves
...
had
...
to
...
be
...
considered
...
in
...
the
...
design.
...
Each
...
ferrous
...
cement
...
baffle
...
will
...
be
...
approximately
...
3.8
...
cm
...
in
...
thickness.
...
The
...
flocculator
...
design
...
program
...
calculates
...
the
...
optimal
...
open
...
space
...
between
...
the
...
baffles
...
to
...
be
...
54.6cm
...
wide.
...
However,
...
due
...
to
...
the
...
design
...
constraint
...
of
...
not
...
being
...
able
...
to
...
put
...
the
...
baffles
...
under
...
an
...
8cm
...
wide
...
ceiling
...
beam
...
that
...
runs
...
horizontally
...
approximately
...
over
...
the
...
middle
...
of
...
tanks
...
C
...
and
...
D,
...
this
...
spacing
...
was
...
not
...
used
...
for
...
all
...
of
...
the
...
baffles.
...
The
...
flow
...
path
...
between
...
baffles
...
in
...
the
...
beginning
...
of
...
tank
...
C
...
is
...
92
...
cm
...
across
...
and
...
the
...
open
...
space
...
between
...
baffles
...
is
...
51.75
...
cm
...
wide,
...
just
...
over
...
3cm
...
closer
...
together
...
than
...
what
...
was
...
recommended.
...
The
...
velocity
...
of
...
the
...
water
...
is
...
determined
...
by
...
the
...
open
...
space
...
between
...
the
...
baffles
...
multiplied
...
by
...
the
...
flow
...
rate,
...
so
...
this
...
smaller
...
distance
...
causes
...
the
...
water
...
to
...
move
...
faster
...
than
...
is
...
recommended
...
through
...
this
...
section
...
of
...
the
...
flocculator.
...
Greater
...
velocities
...
can
...
cause
...
flocs
...
to
...
break
...
up,
...
but
...
since
...
there
...
will
...
be
...
a
...
lot
...
more
...
flocculation
...
occurring
...
after
...
this
...
section
...
with
...
the
...
closer
...
baffles,
...
any
...
flocs
...
that
...
break
...
up
...
should
...
clump
...
together
...
again
...
as
...
they
...
move
...
further
...
along
...
the
...
flocculator.
...
The
...
spacing
...
in
...
this
...
first
...
section
...
of
...
55.25cm
...
when
...
measured
...
from
...
the
...
center
...
of
...
one
...
baffle
...
to
...
the
...
center
...
of
...
the
...
next
...
baffle
...
(on
...
center),
...
and
...
thus
...
taking
...
the
...
baffle
...
thickness
...
into
...
account,
...
keeps
...
any
...
of
...
the
...
baffles
...
from
...
being
...
under
...
the
...
ceiling
...
beam.
...
All
...
the
...
baffles
...
further
...
down
...
the
...
flocculator
...
must
...
be
...
spaced
...
with
...
at
...
least
...
54.6cm
...
of
...
open
...
space
...
between
...
them
...
so
...
that
...
the
...
velocity
...
does
...
not
...
increase
...
thus
...
breaking
...
up
...
more
...
flocs.
...
The
...
baffles
...
on
...
the
...
other
...
side
...
of
...
the
...
ceiling
...
beam
...
in
...
tank
...
C
...
have
...
the
...
program
...
recommended
...
open
...
spacing
...
of
...
54.6
...
cm.
...
The
...
open
...
space
...
measurements
...
were
...
used
...
for
...
the
...
calculation
...
of
...
the
...
velocity
...
because
...
only
...
the
...
area
...
where
...
the
...
water
...
can
...
go
...
matters.
...
The
...
baffles
...
in
...
tank
...
D
...
all
...
have
...
an
...
open
...
spacing
...
between
...
the
...
baffles
...
of
...
66.2
...
cm
...
wide,
...
with
...
an
...
on
...
center
...
spacing
...
of
...
70cm.
...
Since
...
the
...
open
...
space
...
is
...
greater
...
than
...
that
...
recommended
...
by
...
the
...
flocculator
...
design
...
program,
...
only
...
distances
...
which
...
include
...
the
...
baffle
...
thickness
...
matter
...
for
...
the
...
placement
...
of
...
baffles
...
in
...
tank
...
D.
...
A
...
spacing
...
of
...
70cm
...
on
...
center
...
keeps
...
all
...
the
...
baffles
...
out
...
from
...
under
...
the
...
ceiling
...
beam
...
that
...
was
...
discussed
...
previously.
...
The
...
turn
...
from
...
tank
...
C
...
to
...
tank
...
D
...
is
...
treated
...
as
...
a
...
spacing
...
between
...
baffles,
...
thus
...
since
...
the
...
last
...
baffle
...
in
...
tank
...
C
...
has
...
the
...
water
...
flowing
...
under
...
it,
...
the
...
first
...
baffle
...
in
...
tank
...
D
...
has
...
an
...
overflow
...
path.
...
The
...
entrance
...
into
...
tank
...
C
...
from
...
tank
...
B
...
has
...
a
...
water
...
depth
...
of
...
45
...
cm
...
in
...
the
...
existing
...
structure.
...
This
...
pathway
...
will
...
have
...
to
...
be
...
changed
...
so
...
that
...
the
...
water
...
depth
...
is
...
77.2
...
cm
...
above
...
the
...
divider.
...
...
...
lists
...
the
...
spacing
...
between
...
each
...
baffle
...
in
...
tanks
...
C
...
and
...
D
...
in
...
distances
...
measured
...
from
...
the
...
center
...
of
...
each
...
baffle
...
because
...
that
...
is
...
the
...
measurement
...
needed
...
when
...
placing
...
the
...
baffles
...
in
...
the
...
actual
...
tank.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=250px} {anchor:The table} h5. Horizontal Distance between baffles in tanks C and D ||Between baffle #s || Distance on center (cm)|| |Wall between B & C-->1| 73.35| |1-->2 | 55.25 | |2-->3 | 55.25 | |3-->4| 55.25| |4-->5| 58.4| |5-->6| 58.4| |6-->7| 58.4| |U turn| | |Wall @ beginning of tank D -->8| 60| |8-->9| 70| |9-->10|70| |10-->11|70| |11-->12|70| |12-->13|70| {float} |
The
...
opening
...
to
...
the
...
transition
...
channel
...
running
...
from
...
the
...
flocculator
...
to
...
the
...
sedimentation
...
channels
...
will
...
be
...
placed
...
on
...
the
...
side
...
of
...
tank
...
D
...
at
...
the
...
very
...
end
...
of
...
the
...
flocculation
...
system.
...
This
...
opening
...
will
...
be
...
90
...
cm
...
wide
...
(38
...
cm
...
+
...
52
...
cm)
...
and
...
will
...
cut
...
into
...
the
...
area
...
with
...
the
...
ceiling
...
beam
...
by
...
approximately
...
38
...
cm.
...
The
...
rest
...
of
...
the
...
opening
...
will
...
be
...
taken
...
from
...
the
...
wall
...
in
...
tank
...
D.
...
The
...
figures
...
show
...
both
...
the
...
...
and
...
...
views
...
of
...
the
...
transitional
...
chamber.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px} {anchor:side}[!Marcala Plant Design^transition chamber_side view.jpg|width=200px!|Marcala Plant Design^transition chamber_side view.jpg] h5. Side view of the outlet to the transition channel that runs to the sedimentation tank {float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor:top}[!Marcala Plant Design^transition chamber_top view.jpg|width=200px!|Marcala Plant Design^transition chamber_top view.jpg]
h5. Top view of the outlet to the channel that runs to the sedimentation tank drawn by Fred Stottlemyer
{float}
|
The
...
...
...
...
...
...
will
...
have
...
at
...
least
...
a
...
5cm
...
free
...
board
...
and
...
come
...
almost
...
all
...
the
...
way
...
up
...
to
...
the
...
top
...
of
...
the
...
tank.
...
Some
...
room
...
should
...
be
...
left
...
between
...
the
...
top
...
of
...
the
...
"up"
...
baffles
...
and
...
the
...
top
...
of
...
the
...
tank
...
if
...
possible
...
to
...
keep
...
any
...
instances
...
of
...
overflow
...
from
...
flooding
...
out
...
of
...
the
...
tank.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px} {anchor:top of the "up" baffles}[!Marcala Plant Design^baffle layout.jpg|width=200px!|Marcala Plant Design^baffle layout.jpg] h5. Simplified version of 'Up' and 'Down' baffles in flocculator and what the Draining Program considers a 'tank' {float} |
The
...
change
...
in
...
the
...
spacing
...
of
...
tank
...
D's
...
baffles
...
to
...
a
...
distance
...
greater
...
than
...
the
...
value
...
recommended
...
by
...
the
...
MathCAD
...
Flocculator
...
Program
...
created
...
a
...
problem
...
of
...
short
...
circuiting.
...
Utilizing
...
the
...
1.5b
...
rule
...
for
...
the
...
height
...
of
...
the
...
flow
...
path
...
does
...
not
...
allow
...
the
...
"up"
...
and
...
"down"
...
baffles
...
to
...
overlap.
...
The
...
1.5b
...
rule
...
is
...
suggested
...
by
...
Schultz
...
and
...
Okun
...
for
...
the
...
height
...
desirable
...
above
...
the
...
baffles
...
to
...
provide
...
sufficient
...
area
...
for
...
the
...
flocs
...
to
...
remain
...
intact.
...
Using
...
the
...
factor
...
if
...
1.5
...
for
...
the
...
calculation
...
of
...
the
...
height
...
of
...
the
...
flow
...
path
...
for
...
tank
...
D's
...
baffles
...
allows
...
the
...
water
...
to
...
go
...
straight
...
through
...
the
...
tank
...
instead
...
of
...
under
...
and
...
over
...
the
...
baffles.
...
...
...
illustrates
...
the
...
error
...
that
...
results
...
if
...
a
...
baffle
...
spacing
...
of
...
66.2cm
...
and
...
a
...
factor
...
of
...
1.5
...
is
...
used
...
in
...
tank
...
D.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px} {anchor: This figure}[!Marcala Plant Design^short circuit.jpg|width=200px!|Marcala Plant Design^short circuit.jpg] h5. Depiction of short circuiting through the flocculator due to 1.5b rule {float} |
An
...
was
...
added
...
to
...
the
...
end
...
of
...
the
...
flocculator
...
draining
...
programming
...
to
...
calculate
...
factor
...
(f)
...
by
...
which
...
the
...
baffle
...
spacing
...
(b)
...
should
...
be
...
multiplied
...
by
...
to
...
calculate
...
the
...
distance
...
between
...
the
...
bottom
...
of
...
the
...
tank
...
and
...
the
...
bottom
...
of
...
the
...
"up"
...
baffles,
...
which
...
is
...
the
...
same
...
distance
...
between
...
the
...
surface
...
of
...
the
...
water
...
and
...
the
...
top
...
of
...
the
...
"down"
...
baffles.
...
This
...
equation
...
calculates
...
a
...
new
...
f
...
based
...
on
...
the
...
height
...
of
...
the
...
water
...
(water),
...
b,
...
and
...
an
...
"overlap"
...
variable.
...
The
...
"overlap"
...
variable
...
is
...
the
...
amount
...
by
...
which
...
the
...
user
...
wishes
...
the
...
"up"
...
and
...
"down"
...
baffles
...
to
...
vertically
...
overlap
...
so
...
that
...
the
...
bottom
...
of
...
the
...
"up"
...
baffles
...
are
...
below
...
the
...
top
...
of
...
the
...
"down"
...
baffles
...
by
...
this
...
distance.
...
This
...
makes
...
the
...
water
...
go
...
over
...
and
...
under
...
the
...
baffles.
...
The
...
amount
...
of
...
overlap
...
is
...
arbitrary
...
and
...
can
...
be
...
set
...
by
...
the
...
user.
...
This
...
value
...
is
...
set
...
at
...
2cm
...
for
...
the
...
calculation
...
of
...
a
...
new
...
f
...
for
...
tank
...
D.
...
The
...
f
...
factor
...
for
...
the
...
baffles
...
in
...
tank
...
D
...
was
...
calculated
...
with
...
| Anchor | ||||
|---|---|---|---|---|
|
| Include Page | ||||
|---|---|---|---|---|
|
The f for tank D is 1.37, which provides a 2 cm overlap between the "up" and "down" baffles. The height of the flow path is thus 1.37*66.2
...
cm
...
=
...
91
...
cm.
...
Since
...
a
...
factor
...
of
...
1.5
...
is
...
not
...
known
...
to
...
be
...
strictly
...
necessary
...
in
...
order
...
to
...
not
...
break
...
up
...
flocs
...
as
...
they
...
go
...
around
...
the
...
baffles,
...
a
...
factor
...
1.37
...
is
...
considered
...
acceptable
...
at
...
this
...
point.
...
The
...
final
...
baffle
...
spacings
...
for
...
tanks
...
...
and
...
...
are
...
shown
...
in
...
the
...
following
...
figures.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px} {anchor: C}[!Marcala Plant Design^tank C baffles.jpg|width=200px!|Marcala Plant Design^tank C baffles.jpg] h5. Flocculation tank C with dimensions related to the baffles {float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor: D}[!Marcala Plant Design^tank D baffles.jpg|width=200px!|Marcala Plant Design^tank D baffles.jpg]
h5. Flocculation tank D with dimensions related to the baffles
{float}
{cloak}
h4. {toggle-cloak:id=Draining |
Draining the Flocculation Tank
The water treatment plant being built in Marcala, Honduras will have a different flocculation system from others AguaClara has designed. The baffles in the flocculation tanks will be made of 1.5 inch thick ferro cement slabs and these baffles will not be removable. As mentioned, an additional challenge with this design is devising a scheme for draining the flocculation tanks that would not cause short circuiting in the system or take an exorbitant amount of time to drain. A program called Final Floc Draining Time with Forces Calculated was created to model this process.
A simple method of emptying a flocculator tank without removing the baffles is to construct a small hole into the bottom of each down baffle. The size of the hole depends on the desired draining time. The larger the hole, the faster the tank will drain. However, putting a hole in the bottom of each down baffle would allow the flocs to short circuit and cause a new flow path. The holes are modeled as orifices and must have a minimal area, chosen to be less than 1% of the flow path area to minimize the likelihood that they would compromise the flocculation system. The orifices are also staggered to further reduce the risk of short circuiting; the holes will alternate between the left and the right side of the baffles. Another factor in selecting orifice size is the amount of time it would take for the tanks to drain. A compromise must be made between draining time and the increased short circuiting.
A MathCad program was written to model the use of different orifice sizes to #drain a series of connected tanks. The space between each down baffle is treated as an individual tank and the height of the water in each assumed to be equal. At time zero, with the heights of the water even throughout the set of tanks, the only head is the distance between the water height and the outlet valve. As the first tank begins to drain it creates head between it and the next tank causing the second tank to begin to drain which in turn creates head for each consecutive tank. The program calculates the flow rate through each orifice based on the current head then calculates the new height of the water in each tank according to the #equation for orifice flow.
| Anchor | ||||
|---|---|---|---|---|
|
| Include Page | ||||
|---|---|---|---|---|
|
Since all tanks are not only draining but are also receiving water from the adjacent tank (with the exception of the beginning tank) the flow rate used to calculate the water height is the difference between the rate of flow into the tank and the flow rate out of the tank. The water heights during each iteration are calculated using the following #equation.
| Anchor | ||||
|---|---|---|---|---|
|
| Include Page | ||||
|---|---|---|---|---|
|
The program continues to cycle through a while loop until it meets the stopping criteria of which water height in the last tank is sufficiently small. This value is chosen as one thousandth the initial height in the flocculation tank.
| Wiki Markup |
|---|
{float the Flocculation Tank} *Draining the Flocculation Tank* {cloak:id=Draining the Flocculation Tank} The water treatment plant being built in Marcala, Honduras will have a different flocculation system from others AguaClara has designed. The baffles in the flocculation tanks will be made of 1.5 inch thick ferro cement slabs and these baffles will not be removable. As mentioned, an additional challenge with this design is devising a scheme for draining the flocculation tanks that would not cause short circuiting in the system or take an exorbitant amount of time to drain. A program called [Final Floc Draining Time with Forces Calculated|^Floc Draining Time with Forces Calculated 3 - Final.xmcd] was created to model this process. A simple method of emptying a flocculator tank without removing the baffles is to construct a small hole into the bottom of each down baffle. The size of the hole depends on the desired draining time. The larger the hole, the faster the tank will drain. However, putting a hole in the bottom of each down baffle would allow the flocs to short circuit and cause a new flow path. The holes are modeled as orifices and must have a minimal area, chosen to be less than 1% of the flow path area to minimize the likelihood that they would compromise the flocculation system. The orifices are also staggered to further reduce the risk of short circuiting; the holes will alternate between the left and the right side of the baffles. Another factor in selecting orifice size is the amount of time it would take for the tanks to drain. A compromise must be made between draining time and the increased short circuiting. A MathCad program was written to model the use of different orifice sizes to [#drain a series of connected tanks]. The space between each down baffle is treated as an individual tank and the height of the water in each assumed to be equal. At time zero, with the heights of the water even throughout the set of tanks, the only head is the distance between the water height and the outlet valve. As the first tank begins to drain it creates head between it and the next tank causing the second tank to begin to drain which in turn creates head for each consecutive tank. The program calculates the flow rate through each orifice based on the current head then calculates the new height of the water in each tank according to the [#equation for orifice flow]. {anchor:equation for orifice flow} {include:Orifice flowrate} Since all tanks are not only draining but are also receiving water from the adjacent tank (with the exception of the beginning tank) the flow rate used to calculate the water height is the difference between the rate of flow into the tank and the flow rate out of the tank. The water heights during each iteration are calculated using the following [#equation]. {anchor:equation} {include:Height of water as flocculators drain} The program continues to cycle through a while loop until it meets the stopping criteria of which water height in the last tank is sufficiently small. This value is chosen as one thousandth the initial height in the flocculation tank. {float:right|border=2px solid black|width=200px} {anchor: drain a series of connected tanks}[!Marcala Plant Design^tanks draining.jpg|width=200px!|Marcala Plant Design^tanks draining.jpg] h5. Draining of a Flocculator {float} |
Inputs
...
for
...
tank
...
draining
...
program:
...
*h~initial~:
...
1.8m
...
*n~tanks~:
...
4
...
*base:
...
66.2cm
...
*width:
...
92cm
...
*percent_allowable_area:
...
1
...
*height
...
of
...
space:
...
1.4*base
...
The
...
"base"
...
variable
...
refers
...
to
...
the
...
distance
...
between
...
consecutive
...
baffles
...
and
...
the
...
"height_of_space"
...
variable
...
is
...
the
...
distance
...
between
...
the
...
bottom
...
of
...
the
...
up
...
baffles
...
and
...
the
...
floor
...
of
...
the
...
tank
...
in
...
the
...
deepest
...
area
...
of
...
the
...
tank.
...
A
...
"tank"
...
in
...
this
...
program
...
refers
...
to
...
the
...
space
...
between
...
two
...
down
...
baffles.
...
The
...
number
...
of
...
tanks
...
is
...
the
...
number
...
of
...
down
...
baffles
...
plus
...
one
...
for
...
the
...
end
...
wall.
...
The
...
"percent
...
allowable
...
area"
...
is
...
the
...
area
...
of
...
the
...
orifice
...
compared
...
to
...
the
...
area
...
on
...
top
...
of
...
the
...
up
...
baffles
...
(height_of_space*width).
...
An
...
initial
...
vector
...
of
...
orifice
...
diameters
...
is
...
used
...
for
...
the
...
program
...
to
...
loop
...
through.
...
The
...
program
...
outputs
...
several
...
plots
...
describing
...
the
...
relationship
...
of
...
water
...
heights
...
in
...
different
...
tanks.
...
There
...
is
...
also
...
an
...
accompanying
...
...
of
...
the
...
process.
...
Only
...
the
...
orifice
...
sizes
...
that
...
short
...
circuit
...
less
...
than
...
1%
...
the
...
flow
...
are
...
considered.
...
As
...
illustrated
...
in
...
Table
...
2
...
all
...
...
...
considered
...
meet
...
this
...
specification.
...
The
...
forces
...
on
...
each
...
baffle
...
as
...
a
...
result
...
of
...
tank
...
draining
...
are
...
also
...
calculated.
...
This
...
information
...
is
...
useful
...
knowledge
...
for
...
construction
...
as
...
strength
...
requirements
...
for
...
the
...
baffles.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=250px}
{anchor:orifice diameters}
h5. Results of Flocculator Draining Program for Tank D
|| Orifice Diameter (in) || Drainage Time (min) || Percent Area ||
| 0.5 | 383.82 | 0.014 |
| 1 | 95.955 | 0.055 |
| 1.5 | 42.647 | 0.125 |
| 1.75 | 31.332 | 0.17 |
| 2 | 23.989 | 0.222 |
| 2.5 | 15.353 | 0.347 |
{float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px} {anchor: This graph}[!Marcala Plant Design^draining time vs diameter.jpg|width=200px!|Marcala Plant Design^draining time vs diameter.jpg] h5. Tank draining time as a function of the diameter of the orifice {float} [ |
...
...
plots
...
the
...
draining
...
time
...
in
...
minutes
...
that
...
corresponds
...
to
...
each
...
of
...
the
...
possible
...
orifice
...
diameters
...
in
...
inches.
...
As
...
depicted,
...
the
...
time
...
it
...
takes
...
to
...
drain
...
a
...
tank
...
decreases
...
as
...
the
...
size
...
of
...
the
...
hole
...
increases.
...
The
...
hole
...
should
...
be
...
chosen
...
so
...
that
...
the
...
tank
...
drains
...
in
...
an
...
acceptable
...
amount
...
of
...
time.
...
A
...
drainage
...
time
...
of
...
around
...
30
...
minutes
...
is
...
adequate
...
for
...
the
...
Marcala
...
plant.
...
Due
...
to
...
the
...
still
...
evolving
...
design
...
for
...
the
...
baffle
...
spacing
...
in
...
the
...
flocculator
...
tank,
...
only
...
tanks
...
C
...
and
...
D
...
were
...
modeled.
...
These
...
tanks
...
are
...
far
...
enough
...
down
...
the
...
flocculation
...
process
...
that
...
as
...
long
...
as
...
the
...
baffles
...
are
...
spaced
...
either
...
the
...
distance
...
the
...
current
...
flocculator
...
model
...
recommends
...
or
...
further
...
apart,
...
there
...
should
...
not
...
be
...
an
...
issue
...
with
...
flocs
...
breaking
...
up.
...
Since
...
these
...
flocculator
...
tanks
...
have
...
different
...
baffle
...
spacing
...
and
...
different
...
floor
...
heights
...
each
...
tank
...
was
...
analyzed
...
separately.
...
Tank
...
C's
...
draining
...
time
...
was
...
modeled
...
using
...
the
...
54.6cm
...
spacing
...
and
...
4
...
"tanks"
...
(areas
...
between
...
down
...
baffles).
...
These
...
values
...
allow
...
tank
...
C
...
to
...
drain
...
in
...
a
...
little
...
less
...
than
...
17.5
...
minutes
...
with
...
a
...
2
...
inch
...
hole.
...
Tank
...
D
...
takes
...
longer
...
to
...
drain.
...
Though
...
the
...
program
...
calculates
...
the
...
drainage
...
time
...
with
...
a
...
2in
...
orifice
...
as
...
almost
...
24min,
...
the
...
actual
...
drainage
...
time
...
will
...
be
...
a
...
little
...
longer
...
since
...
all
...
of
...
the
...
water
...
in
...
the
...
channel
...
up
...
to
...
the
...
sedimentation
...
tanks
...
will
...
be
...
draining
...
as
...
well.
...
These
...
drainage
...
times
...
are
...
acceptable,
...
so
...
a
...
hole
...
with
...
a
...
2in
...
diameter
...
should
...
be
...
made
...
in
...
the
...
corner
...
of
...
each
...
down
...
baffle,
...
alternating
...
the
...
side
...
of
...
the
...
baffle
...
that
...
the
...
hole
...
is
...
on.
...
Note
...
this
...
is
...
only
...
0.22%
...
of
...
the
...
total
...
flow
...
path
...
area
...
between
...
the
...
bottom
...
of
...
the
...
up
...
baffles
...
and
...
the
...
floor
...
in
...
tank
...
D.
...
This
...
area
...
percentage
...
should
...
keep
...
most
...
of
...
the
...
water
...
from
...
short
...
circuiting
...
by
...
going
...
through
...
this
...
orifice.
...
Since
...
the
...
height
...
of
...
the
...
water
...
changes
...
throughout
...
both
...
tanks
...
due
...
to
...
the
...
sloped
...
floor,
...
the
...
greatest
...
water
...
depth
...
in
...
each
...
tank
...
was
...
used
...
for
...
calculations
...
since
...
this
...
gives
...
a
...
more
...
conservative
...
estimate
...
of
...
drainage
...
time.
...
...
...
shows
...
how
...
the
...
water
...
level
...
in
...
each
...
"tank"
...
responds
...
to
...
draining.
...
The
...
plot
...
of
...
indicates that
...
the
...
"tank"
...
closest
...
to
...
the
...
drain
...
loses
...
water
...
at
...
the
...
fastest
...
rate
...
while
...
the
...
last
...
tank
...
plotted,
...
has
...
a
...
shallower
...
curve
...
indicating
...
a
...
slower
...
draining
...
rate.
...
Note:
...
The
...
'i'
...
variable
...
indicates
...
the
...
entire
...
time
...
over
...
which
...
the
...
tank
...
is
...
draining.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor: This graph}[!Marcala Plant Design^tank draining time.jpg|width=200px!|Marcala Plant Design^tank draining time.jpg]
h5. Tank draining times
{float} |
Calculating Forces on Each Baffle
The force on the baffle is due to the pressure exerted by the water in each tank. The pressure in each 'tank' is depicted #here.
| Wiki Markup |
|---|
{cloak} h4. {toggle-cloak:id=Calculating Forces on Each Baffle} *Calculating Forces on Each Baffle* {cloak:id=Calculating Forces on Each Baffle} The force on the baffle is due to the pressure exerted by the water in each tank. The pressure in each 'tank' is depicted [#here]. {float:right|border=2px solid black|width=200px} {anchor: here}[!Marcala Plant Design^baffle force.jpg|width=200px!|Marcala Plant Design^baffle force.jpg] h5. Calculation of the average pressure on a baffle {float} |
This
...
force,
...
calculated
...
as
...
pressure
...
x
...
area
...
is
...
constantly
...
changing
...
as
...
the
...
water
...
heights
...
decrease
...
when
...
draining
...
the
...
flocculator.
...
...
...
calculates
...
the
...
heights
...
of
...
the
...
water
...
in
...
the
...
flocculator.
...
These
...
values
...
are
...
stored
...
in
...
a
...
table
...
using
...
MathCAD.
...
Using
...
the
...
...
below,
...
the
...
force
...
on
...
each
...
baffle
...
can
...
be
...
calculated
...
as
...
a
...
function
...
of
...
the
...
difference
...
in
...
water
...
heights.
| Include Page | ||||
|---|---|---|---|---|
|
| Include Page | ||||
|---|---|---|---|---|
|
| Wiki Markup |
|---|
{include:water pressure (function of density, g, h)} {include:Force on baffle during tank draining} {float:right|border=2px solid black|width=200px} {anchor:This graph}[!Marcala Plant Design^force on walls.jpg|width=200px!|Marcala Plant Design^force on walls.jpg] h5. Force on Flocculation wall in Newtons for duration of draining of flocculation tank {float} [ |
...
...
illustrates
...
the
...
force
...
on
...
the
...
outside
...
of
...
each
...
baffle
...
in
...
Newtons
...
as
...
a
...
function
...
of
...
time
...
in
...
seconds.
...
The
...
force
...
rapidly
...
reaches
...
a
...
peak
...
then
...
slowly
...
goes
...
down
...
to
...
zero.
...
The
...
further
...
the
...
baffle
...
is
...
from
...
the
...
drain,
...
the
...
less
...
the
...
pressure
...
gradient
...
between
...
two
...
consecutive
...
baffles.
...
When
...
the
...
operator
...
'unplugs'
...
the
...
flocculator,
...
the
...
strongest
...
force
...
exists
...
on
...
the
...
baffle
...
closest
...
to
...
the
...
wall
...
of
...
the
...
flocculator
...
since
...
the
...
difference
...
in
...
head
...
is
...
greatest
...
in
...
the
...
tank
...
that
...
is
...
emptying
...
to
...
waste.
...
Force
...
analysis
...
provides
...
valuable
...
information
...
on
...
the
...
structural
...
parameters
...
of
...
the
...
baffles.
...
Using
...
the
...
above
...
figure,
...
it
...
can
...
be
...
seen
...
that
...
the
...
maximum
...
force
...
exerted
...
on
...
the
...
baffles
...
when
...
draining
...
is
...
1,169
...
lbf
...
(5,200
...
N).
...
Hence
...
the
...
baffles
...
must
...
be
...
designed
...
to
...
withstand
...
this
...
force.
Sloping floor and Drains
Diagrams of the floors in the flocculator were compiled through drawings sent by Fred Stottlemyer and a phone conversation with him. The sloping floors are meant to make draining the flocculators easier and to thoroughly clean out any floc build up on the bottom on the flocculation tanks.
Tanks #A, #B, #C and #D will have a floor with a downward slope of roughly 10 cm over the length of each section. Tank A will begin at 58 cm above the current floor, tank B will begin at 48 cm above the current floor, and tank C will begin 35 cm above the current floor. Tank D starts at the height that tank C ends at and slopes down to 15cm above the original floor. The diagrams are shown at the end of the drainage section.
Included in the tank drawings are the drain placements in the flocculator system. There are three main drains in the series of tanks. One is on the side of tank B just before tank C. Another one is at the end of tank C and the last drain is in the floor of tank D at the end of the tank. This last drain connects to a 4 inch pipe running under the floor of tank D with a 90 degree elbow. The water then leaves the system through the wall at the beginning of tank D. The pipe has a downward slope with the beginning being at a height of 15 cm and the end at 5 cm above the original floor level where it then drains out of the side of the tank. These drains have already been placed in the Marcala plant in anticipation of a sloped floor.
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{cloak} h4. {toggle-cloak:id=Sloping floor and Drains} *Sloping floor and Drains* {cloak:id=Sloping floor and Drains} Diagrams of the floors in the flocculator were compiled through drawings sent by Fred Stottlemyer and a phone conversation with him. The sloping floors are meant to make draining the flocculators easier and to thoroughly clean out any floc build up on the bottom on the flocculation tanks. Tanks [#A], [#B], [#C] and [#D] will have a floor with a downward slope of roughly 10 cm over the length of each section. Tank A will begin at 58 cm above the current floor, tank B will begin at 48 cm above the current floor, and tank C will begin 35 cm above the current floor. Tank D starts at the height that tank C ends at and slopes down to 15cm above the original floor. The diagrams are shown at the end of the drainage section. Included in the tank drawings are the drain placements in the flocculator system. There are three main drains in the series of tanks. One is on the side of tank B just before tank C. Another one is at the end of tank C and the last drain is in the floor of tank D at the end of the tank. This last drain connects to a 4 inch pipe running under the floor of tank D with a 90 degree elbow. The water then leaves the system through the wall at the beginning of tank D. The pipe has a downward slope with the beginning being at a height of 15 cm and the end at 5 cm above the original floor level where it then drains out of the side of the tank. These drains have already been placed in the Marcala plant in anticipation of a sloped floor. {float:right|border=2px solid black|width=200px} {anchor:A}[!Marcala Plant Design^Tank A.jpg|width=200px!|Marcala Plant Design^Tank A.jpg] h5. Flocculation tank A with tank dimensions {float} |
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h5. Flocculation tank B with tank dimensions
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h5. Flocculation tank C with tank dimensions
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{float:right|border=2px solid black|width=200px} {anchor:D}[!Marcala Plant Design^Tank D.jpg|width=200px!|Marcala Plant Design^Tank D.jpg] h5. Flocculation tank D with tank dimensions {float} {cloak} {cloak} h2. {toggle-cloak:id=Sedimentation Tank} {color:green}{*}Marcala Sedimentation Details{*}{color} {cloak:id=Sedimentation Tank} h4. {toggle-cloak:id=Sedimentation Tank} *Sedimentation Tank* {cloak:id=Sedimentation Tank} | {anchor:sedimentation tanks}[!Sedimentation Tank^Microsoft PowerPoint - Marcala Sedimentation Tank Dimensions.jpg!|Sedimentation Tank^ Microsoft PowerPoint - Marcala Sedimentation Tank Dimensions.jpg] h5.Marcala Sedimentation Tank Dimensions | Due to previous constraints, each sedimentation tank's area was given to be 105 cm wide by 240 cm long, expect for the last sedimentation tank which will be 265cm. Since the flow will be split into eight different sedimentation tanks, the flow rate that each manifold must accommodate is 189 L/min. The width of the plate settlers is determined by the width of each tank. Other assumptions are listed below. They are all based on recommendations from previous AguaClara plants. A MathCAD program was also utilized to calculate the needed parameter. Assumptions * Lamella Length: 36 in * Lamella spacing: 5 cm * Angle of Plate Settlers alpha: 60º * Depth: 2 m The sloping of the plate settlers will create an 'inactive' length in the sedimentation tank. This length is equal to , depicted below. This value was calculated to be 45.7 cm and must be subtracted from the tank length since sedimentation will not take place in this area. Since the length of the tank is 240 cm long, the active area of sedimentation will be 194 cm. The diagram below presents this concept. | {anchor:sedimentation tanks}[!Marcala Plant Design^Microsoft Word - MARCALA 12.jpg!|Marcala Plant Design^Microsoft Word - MARCALA 12.jpg] h5. Mathematical Parameters in Dedimentation Tank| This will allow for plate settlers to be installed. The upwards velocity in the tank allows for the critical velocity in each tank to be calculated. The critical velocity, Vc, denotes the maximum amount of time required to just capture a particle. Sources such a Schultz and Okuni recommend critical velocities between 20-60 m/day. The critical velocity for our designed sedimentation tanks during normal operation was calculated to be 17.08 m/day using the equations below. Through experience with the plant in Ojojona, it has been suggested to keep the critical velocity below 15 m/day. If the critical velocity is too high, it is believed that flocs tend to rise instead of settle. When two sedimentation tanks are offline (two drain at the same time, discussed below), the critical velocity in the other six will increase if the flow through plant remains constant. Alternatively, the flow rate into the plant could be reduced temporarily while the sedimentation tanks are draining. {include:Sedimentation Tank Upwards Velocity} Design parameters for the sedimentation tank are below. * Depth: 2 m * Vc: 13.06 m/day * Vup: 116.51 m/day * Vc: 22.77 m/day, with two tanks offline * Vup: 203.1 m/day, with two tanks offline\+ * Qtank : 189.27 L/min \+\* Qtank: 83.3gpm with two sedimentation tanks offline\+ * ¿: 60 degrees * Width: 102cm * Llamella: length of lamella 36in * L: Total Length, 2.65 m * Lacutal: Active Length, 2.20 m * blamella: Lamella Spacing, 5 cm * Number of Plate Settlers: 38 * Wall Height: 2.3 m | {anchor:sedimentation tanks}[!Marcala Plant Design^sedimenationtankparameters.JPG!|Marcala Plant Design^sedimenationtankparameters.JPG] h5. Marcala Sedimentation Tank Parameters | {cloak} h4. {toggle-cloak:id=Sludge Removal for the Marcala Plant} *Sludge Removal for the Marcala Plant* {cloak:id=Sludge Removal for the Marcala Plant} A sludge removal system must also be designed. The current experimental system in Ojojona has confirmed the success of using a manifold at the bottom on the sedimentation tank to remove sludge build up. This manifold will have several small orifices to equally pull sludge out of the bottom of the sedimentation tank. Furthermore, by sloping the sides of the sedimentation tank below the plate settlers to a central valley, more sludge is likely to be removed. Figure 4 depicts end view of 10 sedimentation tanks showing the proposed sludge removal system. Note that each two successive sedimentation tanks are tied in series. This will cause two sedimentation tanks to drain at the same time. | {anchor:sedimentation tanks}[!Marcala Plant Design^SludgeRemovalSystem.jpg!|Marcala Plant Design^SludgeRemovalSystem.jpg] h5. Proposed Sludge Removal System| The water depth in the sedimentation tank will remain at 2 m measured from the water surface to the bottom of the drain pipe. +The drain pipe will have an orifice in the top of the pipe spaced every 10 cm+, this distance was chosen as a conservative measure to collect sludge evenly. Accumulated sludge is pulled out from the entire bottom of the tank while clean water is carried out of the tank by the effluent launder. The drain pipe will have , or 26 orifices to drain the sludge. The diameter of the sludge manifold is found by an iterative process using the following equation. {include:Manifold diameter} Where * The projected flow through the manifold when draining is estimated at double the average drain flow rate divided by the number of sedimentation tanks. The extra factor of two is because two tanks will drain at one time. This design specification was employed so that although there are eight sedimentation tanks, there are effectively only four draining tanks. This way the walls dividing the four tanks into two did not need to be built strong enough to withstand the force of water pushing outwards. Figure 25 is a photo from Fred Stottlemyer of the current sludge drains and how they are connected to one another. Note that the photo depicts two adjacent sedimentation tanks which will drain together. +Equation 17+ {anchor:sedimentation tanks}[!Marcala Plant Design^SludgeRemovalSystempic.jpg!|Marcala Plant Design^SludgeRemovalSystempic.jpg] |h5.Proposed Sludge Removal System. The three influent pipes can also be seen entering the sedimentation tank. Note that these influent pipes enter the tank horizontally because the channel is located outside of the sedimentation tank.| The three influent pipes can also be seen entering the sedimentation tank. Note that these influent pipes enter the tank horizontally because the channel is located outside of the sedimentation tank. * {include:Swamee-Jain#equation]calculates the friction factor caused by shear within the pipes} {anchor:equation} {include:f Swamee-Jain}|f Swamee-Jain} &linkCreation=true&fromPageId=12160204" |
Marcala Transition from Flocculation to Sedimentation
The depth of the channel connecting the flocculation tanks to the sedimentation tanks was needed. The channel must be designed so as to make sure that the transition between the two tanks does not break up the flocs formed in the flocculation tank. Another constraint to include in design is to ensure proper depth as the plant operator will need to cap the sedimentation inlet pipes when draining a sedimentation tank.
The design process began with the consideration of the equation of velocity gradient as a function head loss, velocity and residence time.
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The head loss equation accounting for minor and major losses dictate the flow in the channel
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Rewriting the above two equations, the following equation is derived
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The residence time is a function of length and velocity in the reactor
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Assuming that minor losses dominate the following equation is obtained from the combination of the above two equations:
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This equation must be used to solve for the required area of the channel, and then obtain the height of the channel given the flow rate.
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A reasonable distance over which the energy from the minor losses is dissipated, L, when the flow goes around the 90 degree bend and into the channel must be determined to solve this equation. We assumed that this dissipation occurs over a length that is double the width of the channel giving us equation below.
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Additionally, the head loss coefficient for a 90 degree bend is approximately 0.5 (assuming it is like a pipe installed flush with the wall of a tank). The existing infrastructure restricted the width of the channel to 45 cm. A velocity of 0.093 m/s in the channel was calculated by setting the channel velocity gradient to be 15 /s, equal to the desired at the end ofthe flocculation process.
The flow in the channel should be ½ the total flow of the plant because the flow is split into two directions. The final height of the channel was calculated to be 37.6 cm given that the length needed to dissipate the energy from head loss was double the channel width.
Design parameters for the transition channel:
- Expected Gbar: 15/s
- Flow rate in each ½ of the channel: 250 gpm
- Dissipation Length: 90.0 cm
- Depth: 37.6 cm
- Width: 45.0 cm
- Total Length: 10 m
Marcala Sedimentation Details
Sedimentation Tank
Due to previous constraints, each sedimentation tank's area was given to be 105 cm wide by 240 cm long, expect for the last sedimentation tank which will be 265cm. Since the flow will be split into eight different sedimentation tanks, the flow rate that each manifold must accommodate is 189 L/min. The width of the plate settlers is determined by the width of each tank. Other assumptions are listed below. They are all based on recommendations from previous AguaClara plants. A MathCAD program was also utilized to calculate the needed parameter.
Assumptions
- Lamella Length: 36 in
- Lamella spacing: 5 cm
- Angle of Plate Settlers alpha: 60º
- Depth: 2 m
The sloping of the plate settlers will create an 'inactive' length in the sedimentation tank. This length is equal to , depicted below. This value was calculated to be 45.7 cm and must be subtracted from the tank length since sedimentation will not take place in this area. Since the length of the tank is 240 cm long, the active area of sedimentation will be 194 cm. The diagram below presents this concept.
This will allow for plate settlers to be installed. The upwards velocity in the tank allows for the critical velocity in each tank to be calculated. The critical velocity, Vc, denotes the maximum amount of time required to just capture a particle. Sources such a Schultz and Okuni recommend critical velocities between 20-60 m/day. The critical velocity for our designed sedimentation tanks during normal operation was calculated to be 17.08 m/day using the equations below.
Through experience with the plant in Ojojona, it has been suggested to keep the critical velocity below 15 m/day. If the critical velocity is too high, it is believed that flocs tend to rise instead of settle. When two sedimentation tanks are offline (two drain at the same time, discussed below), the critical velocity in the other six will increase if the flow through plant remains constant. Alternatively, the flow rate into the plant could be reduced temporarily while the sedimentation tanks are draining.
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Design parameters for the sedimentation tank are below.
- Depth: 2 m
- Vc: 13.06 m/day
- Vup: 116.51 m/day
- Vc: 22.77 m/day, with two tanks offline
- Vup: 203.1 m/day,
with two tanks offline+ - Qtank : 189.27 L/min
+* Qtank: 83.3gpm with two sedimentation tanks offline+ - ¿: 60 degrees
- Width: 102cm
- Llamella: length of lamella 36in
- L: Total Length, 2.65 m
- Lacutal: Active Length, 2.20 m
- blamella: Lamella Spacing, 5 cm
- Number of Plate Settlers: 38
- Wall Height: 2.3 m
Sludge Removal for the Marcala Plant
A sludge removal system must also be designed. The current experimental system in Ojojona has confirmed the success of using a manifold at the bottom on the sedimentation tank to remove sludge build up. This manifold will have several small orifices to equally pull sludge out of the bottom of the sedimentation tank. Furthermore, by sloping the sides of the sedimentation tank below the plate settlers to a central valley, more sludge is likely to be removed. Figure 4 depicts end view of 10 sedimentation tanks showing the proposed sludge removal system. Note that each two successive sedimentation tanks are tied in series. This will cause two sedimentation tanks to drain at the same time.
The water depth in the sedimentation tank will remain at 2 m measured from the water surface to the bottom of the drain pipe. The drain pipe will have an orifice in the top of the pipe spaced every 10 cm, this distance was chosen as a conservative measure to collect sludge evenly. Accumulated sludge is pulled out from the entire bottom of the tank while clean water is carried out of the tank by the effluent launder. The drain pipe will have , or 26 orifices to drain the sludge.
The diameter of the sludge manifold is found by an iterative process using the following equation.
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Where
- The projected flow through the manifold when draining is estimated at double the average drain flow rate divided by the number of sedimentation tanks. The extra factor of two is because two tanks will drain at one time. This design specification was employed so that although there are eight sedimentation tanks, there are effectively only four draining tanks. This way the walls dividing the four tanks into two did not need to be built strong enough to withstand the force of water pushing outwards. Figure 25 is a photo from Fred Stottlemyer of the current sludge drains and how they are connected to one another. Note that the photo depicts two adjacent sedimentation tanks which will drain together.
Equation 17
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Proposed Sludge Removal System. The three influent pipes can also be seen entering the sedimentation tank. Note that these influent pipes enter the tank horizontally because the channel is located outside of the sedimentation tank. |
The three influent pipes can also be seen entering the sedimentation tank. Note that these influent pipes enter the tank horizontally because the channel is located outside of the sedimentation tank.
Include Page Swamee-Jain Swamee-Jain
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The headloss through the manifold changes as it goes by each port, but for simplification we assume flow into each port is identical.
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The velocity head at the end of the manifold is calculated as shown.
Equation 22
Design parameters for the sedimentation sludge manifold are as follows.
- Space between Orifices: 10 cm
- n , Number of Orifices on each manifold: 26
- Time to Empty Tank: 45 min
- Qratio - Ratio of flow between first and last orifice: 0.80
- Qdrain - Maximum drain flow rate: 126.9gpm
- - Head loss through the manifold: 8.89 cm
- - The velocity head: 15.73 cm
- - Head loss allowable through the orifices: 2m- - =175.38 cm
- Dmanifold - Diameter of Pipe: 3.0 in
- Orifice Diameter: 0.287 in
Note: The exact positions of how the sides of the bottom of the sedimentation tank slopes (to help accumulate sludge in the drain pipe) and the interaction with the inlet pipes from the transition channel have not yet been specified.
Effluent Launder
The effluent launder will carry water out of the sedimentation tank to be chlorinated and stored in a tank for distribution. A similar program used to calculate the sludge drain was used. The launders leaving the sedimentation tanks are designed in a similar manner as the sedimentation sludge drain manifold. There will be orifices on both sides of the launder spaced between every other plate settler. The launder flow rate is the flow rate in each sedimentation tank, the plant flow rate divided by eight. By using salvaged pipe for the launder, the pipe launder diameter was specified to be 6in diameter. UsingEquation 11 Equation 12
and by setting the depth under the water elevation for the effluent launder to be 10cm, the allowable head loss is calculated. The depth of the launder is specified at 10cm through an iterative process in order to confirm the use of 6in pipe diameter is accurate using Equation 16 calculates the orifice diameter using the allowable headloss and flow rate through each orifice.
Design parameters for the sedimentation tank effluent launders are as follows.
- Qratio: 0.95
- Launder Length: 2.65 m
- Launder/ Exit Pipe Diameter: 6 in
- Head loss in the launder (not including head loss to the plant level tank): 10cm
- Total number of orifices: =38, with two on each side of the launder, spaced above every other plate settler
- Spacing between orifices: = 11.55 cm (two rows of orifices with this spacing!)
- Head loss through the manifold: 0.036 cm
- Velocity head: 0.238cm
- Head loss through the orifices: 10cm- - =9.726cm
- Orifice size: 1.232 cm
Marcala Plant Regulator Tank
The plant regulator tank (PRT) will connect all effluent tubes from the sedimentation tanks into one tank that will incorporate chlorination and discharge the chlorinated water to the distribution tank. This tank will regulate the water level in the sedimentation tanks. Currently, there are 5 pairs of sedimentation tanks, each with an effluent pipe collecting the clean water. Each effluent pipe will connect to form 5 pipes that lead into the PRT. The water from each pipe will enter the PRT through the bottom of the tank which will enable easy capping of the pipes in order to shut off one pair of sedimentation tanks for cleaning. Water will exit the tank through a pipe sticking up through the base of the tank. The height of this pipe can be adjusted in the future if a change in the water levels or flowrate of the plant if necessary. The rim of the pipe will function as a weir to control the level of the water.