...
Floating
...
Flocs
...
Team
...
Experimental
...
Set-up
...
(Summer
...
2009)
System Modifications
The experimental setup used in Spring 2009 was modified at the beginning of the summer to include a taller pressurized aerator in order to increase the residence time of the bubbles and to establish more consistent supersaturation in the water going to the sand filter. The new aerator includes a valve to release water to maintain the appropriate water level. The hot and cold water valves present in the original set-up have been omitted in the new one, and the water source has been changed to a container with water whose temperature is maintained at 20 degrees Celsius. Since the aerator is pressured throughout the experiments, a pump was added before the aerator to force water into the system. The PID flow accumulator used in the previous set up was effectively replaced by a pump that now controls the flow rate through the sand filter. While the flow accumulator no longer controls the flow rate of the system, it has been kept as part of the setup in order to even out flow rate fluctuations from the pump and also to collect any bubbles coming through the line into the sand filter. A temperature probe is used just to confirm that the water temperature is 20 degrees Celsius. From there, the water flows up through the sand filter, and then to the bubble collector, as in the Spring 2009 setup.
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h3. System Modifications The [experimental setup|Sand Filter Diagram] used in Spring 2009 was modified at the beginning of the summer to include a taller pressurized aerator in order to increase the residence time of the bubbles and to establish more consistent supersaturation in the water going to the sand filter. The new aerator includes a valve to release water to maintain the appropriate water level. The hot and cold water valves present in the original set-up have been omitted in the new one, and the water source has been changed to a container with water whose temperature is maintained at 20 degrees Celsius. Since the aerator is pressured throughout the experiments, a pump was added before the aerator to force water into the system. The flow that leaves the aerator and enters the sand filter is regulated by a valve that is controlled by the PID flow accumulator used in the previous setup. A temperature probe is used just to confirm that the water temperature is 20 degrees Celsius. From there, the water flows up through the sand filter, and then to the bubble collector, as in the [Spring 2009 setup|Sand Filter Diagram]. {anchor:Figure 1} {float:right|border="220" solid whitegrey}[!updated schematic copy.png|width="745", height="384"!|Floating Floc Summer 2009 Setup Schematic] h5. Figure 1: Current experimental apparatus (Summer 2009) {float} |
The
...
Process
...
Controller
...
software
...
is
...
used
...
to
...
automate
...
experiments
...
and
...
record
...
data
...
on
...
Microsoft
...
Excel
...
spreadsheets.
...
Two
...
states
...
have
...
been
...
developed
...
for
...
the
...
experimental
...
setup
...
-
...
an
...
"On"
...
and
...
an
...
"Off"
...
state.
...
Generally,
...
experiments
...
will
...
be
...
run
...
with
...
the
...
system
...
on
...
the
...
"On"
...
state.
...
However,
...
as
...
experiments
...
are
...
conducted,
...
it
...
may
...
be
...
necessary
...
to
...
increase
...
the
...
number
...
of
...
states.
...
A
...
rough
...
draft
...
of
...
the
...
Process
...
Controller
...
configuration
...
file
...
to
...
be
...
used
...
can
...
be
...
found
...
...
.
In the "On"
...
state,
...
water
...
from
...
the
...
temperature-regulated
...
source
...
flows
...
into
...
the
...
aerator
...
until
...
the
...
water
...
level
...
reaches
...
a
...
certain
...
height
...
that
...
is
...
yet
...
to
...
be
...
established.
...
This
...
maximum
...
height
...
(set
...
point:
...
Aerator
...
Max
...
Water
...
Level)
...
is
...
limited
...
by
...
the
...
water
...
level
...
indicator
...
system
...
on
...
the
...
aerator,
...
which
...
measures
...
the
...
difference
...
between
...
the
...
air
...
pressure
...
in
...
the
...
system
...
and
...
the
...
water
...
pressure.
...
The
...
water
...
level
...
should
...
not
...
reach
...
the
...
tube
...
connecting
...
the
...
headspace
...
of
...
the
...
aerator
...
to
...
the
...
pressure
...
sensor.
...
If
...
the
...
maximum
...
water
...
level
...
is
...
exceeded,
...
a
...
valve
...
is
...
opened
...
to
...
release
...
the
...
excess
...
water
...
until
...
a
...
minimum
...
set
...
water
...
level
...
(set
...
point:
...
Aerator
...
Min
...
Water
...
Level)
...
is
...
reached.
...
(See
...
set
...
point:
...
Aerator
...
Water
...
Wasting
...
Control
...
for
...
method
...
governing
...
the
...
water
...
release
...
valve.)
...
During
...
experiments,
...
the
...
aerator
...
is
...
kept
...
in
...
the
...
range
...
of
...
100
...
kPa
...
-
...
102 kPa
...
gage
...
pressure
...
in
...
order
...
to
...
achieve
...
consistent
...
dissolved
...
gas
...
concentrations.
...
The
...
air
...
pressure
...
regulator
...
valve
...
functions
...
much
...
like
...
the
...
water
...
level
...
regulating
...
valve
...
control
...
for
...
the
...
aerator
...
mentioned
...
above.
...
(See
...
set
...
point:
...
Aerator
...
Air
...
Release
...
Control
...
for
...
method
...
governing
...
the
...
air
...
release
...
valve.)
...
When
...
the
...
pressure
...
is
...
below
...
the
...
maximum
...
set
...
pressure
...
(set
...
point:
...
Aerator
...
Max
...
Air
...
Pressure
...
-
...
102 kPa),
...
the
...
valve
...
will
...
remain
...
closed.
...
Once
...
the
...
maximum
...
pressure
...
is
...
reached,
...
the
...
valve
...
will
...
open
...
until
...
the
...
minimum
...
set
...
pressure
...
(set
...
point:
...
Aerator
...
Min
...
Air
...
Pressure
...
-
...
100
...
kPa)
...
is
...
reached.
...
To
...
control
...
the
...
flow
...
of
...
air
...
leaving
...
the
...
system,
...
a
...
rotameter
...
is
...
connected
...
after
...
the
...
air
...
release
...
valve.
...
The
...
flow
...
of
...
supersaturated
...
water
...
exiting
...
the
...
aerator
...
is
...
regulated
...
by
...
a
...
valve
...
that
...
is
...
controlled
...
by
...
the
...
PID
...
flow
...
accumulator.
...
The
...
flow
...
rate
...
can
...
be
...
adjusted
...
in
...
Process
...
Controller
...
by
...
editing
...
the
...
set
...
point
...
"Flow
...
Rate",
...
which
...
is
...
the
...
target
...
value
...
of
...
the
...
PID
...
control
...
algorithm.
...
The
...
water
...
leaving
...
the
...
aerator
...
is
...
then
...
sent
...
up
...
through
...
the
...
sand
...
filter
...
and
...
out
...
to
...
the
...
bubble
...
collector,
...
which
...
measures
...
the
...
amount
...
of
...
gas
...
removed
...
by
...
the
...
sand
...
filter.
...
The
...
bubble
...
collector
...
has
...
two
...
valves
...
-
...
a
...
water
...
outflow
...
valve
...
and
...
an
...
air
...
valve.
...
At
...
the
...
start
...
of
...
each
...
experiment,
...
the
...
bubble
...
collector
...
is
...
filled
...
with
...
water
...
to
...
a
...
level
...
that
...
will
...
be
...
determined
...
experimentally
...
(set
...
point:
...
Bubble
...
C.
...
Max
...
Water
...
Level).
...
The
...
bubble
...
collector
...
uses
...
the
...
same
...
sort
...
of
...
water
...
level
...
indicator
...
system
...
as
...
the
...
aerator;
...
the
...
water
...
level
...
in
...
the
...
bubble
...
collector
...
is
...
limited
...
by
...
the
...
location
...
of
...
the
...
tube
...
connecting
...
the
...
headspace
...
to
...
the
...
pressure
...
sensor.
...
During
...
the
...
process
...
of
...
filling
...
the
...
bubble
...
collector,
...
the
...
air
...
valve
...
is
...
opened
...
and
...
the
...
water
...
outflow
...
valve
...
is
...
closed,
...
allowing
...
for
...
natural
...
refilling
...
of
...
the
...
apparatus.
...
When
...
the
...
maximum
...
water
...
level
...
is
...
reached,
...
the
...
air
...
valve
...
is
...
shut
...
and
...
the
...
water
...
outflow
...
valve
...
is
...
opened,
...
causing
...
a
...
partial
...
vacuum
...
at
...
the
...
top
...
of
...
the
...
collector
...
that
...
holds
...
the
...
column
...
of
...
water
...
up.
...
As
...
water
...
flows
...
through
...
the
...
bubble
...
collector,
...
gas
...
bubbles
...
in
...
the
...
influent
...
water
...
slowly
...
increase
...
the
...
pressure
...
in
...
the
...
bubble
...
collector,
...
causing
...
the
...
water
...
level
...
to
...
decrease
...
to
...
a
...
minimum
...
level
...
(set
...
point:
...
Bubble
...
C.
...
Min
...
Water
...
Level).
...
Once
...
this
...
minimum
...
level
...
is
...
reached,
...
the
...
system
...
refills
...
by
...
the
...
same
...
process.
...
(See
...
set
...
points:
...
Bubble
...
C.
...
Water
...
Outflow
...
Valve
...
and
...
Bubble
...
C.
...
Air
...
Valve
...
for
...
methods
...
governing
...
the
...
water
...
outflow
...
valve.)
...
In
...
the
...
"Off"
...
state,
...
the
...
water
...
release
...
valve
...
and
...
the
...
air
...
valve
...
in
...
the
...
aerator
...
are
...
opened
...
to
...
prevent
...
the
...
build-up
...
of
...
pressure.
...
The
...
flow
...
valve
...
that
...
allows
...
water
...
out
...
of
...
the
...
aerator
...
and
...
into
...
the
...
sand
...
filter
...
is
...
closed
...
and
...
the
...
air
...
valve
...
and
...
water-out
...
valve
...
in
...
the
...
bubble
...
collector
...
is
...
opened
...
to
...
drain
...
the
...
bubble
...
collector.