...
Evaluation
...
of
...
previous
...
experiments
...
with
...
the
...
new system
Objective
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system h2. Objective {float:right|border=2px solid white|width=120px} !Aerator (Before 4 Stones).jpg! h6. The aerator at the beginning of Summer 2009 {float} |
This
...
set
...
of
...
experiments
...
attempted
...
to
...
replicate
...
the
...
grain
...
size
...
research
...
performed
...
with
...
the
...
...
...
...
,
...
to
...
assess
...
both
...
the
...
functionality
...
of
...
the
...
new
...
system
...
and
...
the
...
validity
...
of
...
the
...
Spring
...
2009
...
results.
...
Additionally,
...
dissolved
...
oxygen
...
measurements
...
were
...
taken
...
to
...
evaluate
...
the
...
effectiveness
...
of
...
each
...
of
...
the
...
components
...
in
...
the
...
setup
...
with
...
respect
...
to
...
theoretical
...
expectations.
...
According
...
to
...
the
...
...
...
...
...
...
...
...
,
...
it
...
is
...
predicted
...
that
...
around
...
18
...
mL
...
of
...
bubbles
...
will
...
be
...
formed
...
for
...
1
...
L
...
of
...
water
...
that
...
has
...
been
...
previously
...
exposed
...
to
...
1
...
atm
...
gage
...
pressure
...
at
...
temperature
...
of
...
25
...
ËšC.
...
See
...
Figure
...
1.
...
for
...
the
...
relationship
...
between
...
the
...
theoretical
...
bubble
...
formation
...
potential
...
and
...
initial
...
air
...
pressure
...
with
...
which
...
the
...
water
...
reached
...
equilibrium
...
before
...
returning
...
to
...
atmospheric
...
pressure.
...
For
...
the
...
current
...
aerator,
...
it
...
was
...
assumed
...
for
...
the
...
sake
...
of
...
calculation
...
that
...
the
...
dissolved
...
gas
...
concentration
...
would
...
reach
...
equilibrium
...
with
...
the
...
pressure
...
in
...
the
...
aerator,
...
resulting
...
in
...
18
...
mg/L
...
of
...
dissolved
...
gas
...
in
...
the
...
water
...
flowing
...
into
...
the
...
sand
...
filter.
...
While
...
a
...
theoretical
...
model
...
of
...
gas
...
removal
...
by
...
the
...
sand
...
filter
...
has
...
not
...
been
...
developed,
...
the
...
team
...
believed
...
that
...
the
...
abundant
...
surface
...
area
...
provided
...
by
...
the
...
sand
...
would
...
remove
...
gas
...
by
...
providing
...
ample
...
nucleation
...
sites
...
for
...
bubbles,
...
and
...
sites
...
at
...
which
...
bubbles
...
could
...
adhere
...
to
...
a
...
surface
...
and
...
aggregate.
...
General
...
Procedure
...
For
...
the
...
two
...
experiments
...
listed
...
below,
...
the
...
same
...
procedure
...
was
...
used
...
with
...
a
...
different
...
size
...
of
...
sand
...
grain
...
used
...
in
...
each.
...
Sand
...
40
...
(0.49
...
mm
...
-
...
0.57
...
mm)
...
and
...
Sand
...
30
...
(0.59
...
mm
...
-
...
0.84
...
mm)
...
were
...
used
...
for
...
Experiments
...
1
...
and
...
2,
...
respectively.
...
The
...
details
...
of
...
the
...
procedure
...
are
...
available
...
here.
Results and Discussion
Experiments 1 and 2 were performed to assess whether the new system collects consistent data and to ensure that previous sand grain experiments results are replicable, and thus are valid. We performed the control experiment (with no sand) after we observed that the measured rate gas removal in the sand filter was less than 18 mg/L, the theoretical rate of gas removal. When we realized that gas removal was less than expected, we took the dissolved oxygen measurements to determine which component of the system was not functioning effectively.
Reruns of the Previous Fluidized Bed Experiments
- Experiment 1 was performed shortly after the new setup was installed. Sand 40 was used to evaluate previous grain size results.
- Experiment 2 was performed after the system was modified to account for problems that arose in Experiment 1. Sand 30 was used with the purpose of testing the functionality again and evaluating previous results.
- A control Experiment (i.e., one with no sand) was performed to evaluate the sand filter's effectiveness by measuring gas removal in the absence of sand.
- When we had confirmed that the measured gas removal values were less than theoretical values, we measured the concentrations of dissolved oxygen at various points in the experimental apparatus. We found that the measurements taken at a point just past the sand filter showed dissolved oxygen concentrations that were higher than that of water going into the sand filter. This suggested a problem with either the setup or the fluidized bed mechanism. Pressure through the sand filter was calculated to explain that large head loss through the system in combination with pressure build up in the filter was not resulting in tiny bubbles being reincorporated into solution. The results of the headloss calculations can be found here. With the control experiment, we confirmed that the sand filter was not suitable for gas removal because the material properties of the sand are not conducive for removing gas.
General Conclusions
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|FF Procedure for Evaluation of Previous Experiments]. h2. Results and Discussion Experiments 1 and 2 were performed to assess whether the new system collects consistent data and to ensure that previous sand grain experiments results are replicable, and thus are valid. We performed the control experiment (with no sand) after we observed that the measured rate gas removal in the sand filter was less than 18 mg/L, the theoretical rate of gas removal. When we realized that gas removal was less than expected, we took the [dissolved oxygen measurements|FF Dissolved Oxygen Measurements] to determine which component of the system was not functioning effectively. [Reruns of the Previous Fluidized Bed Experiments] * Experiment 1 was performed shortly after the new setup was installed. Sand 40 was used to evaluate [previous grain size results|Fluidized Bed after Super Saturator]. * Experiment 2 was performed after the system was modified to account for problems that arose in Experiment 1. Sand 30 was used with the purpose of testing the functionality again and evaluating previous results. * A control Experiment (i.e., one with no sand) was performed to evaluate the sand filter's effectiveness by measuring gas removal in the absence of sand. [Dissolved Oxygen Measurements|FF Dissolved Oxygen Measurements] * When we had confirmed that the measured gas removal values were less than theoretical values, we measured the concentrations of dissolved oxygen at various points in the experimental apparatus. We found that the measurements taken at a point just past the sand filter showed dissolved oxygen concentrations that were higher than that of water going into the sand filter. This suggested a problem with either the setup or the fluidized bed mechanism. Pressure through the sand filter was calculated to explain that large head loss through the system in combination with pressure build up in the filter was not resulting in tiny bubbles being reincorporated into solution. The results of the headloss calculations can be found [here|^Head loss calculations Sand Filter Summer 09.xmcd]. With the control experiment, we confirmed that the sand filter was not suitable for gas removal because the material properties of the sand are not conducive for removing gas. h2. General Conclusions {anchor:Figure 2} {float:right|border=12px solid white|width="372", height="289"} !Theoretical bubble formation potential.png! h6. Figure 1: Theoretical bubble formation potential {float} |
Experiments
...
using
...
Sand
...
40
...
and
...
Sand
...
30
...
showed
...
rates
...
of
...
gas
...
removal
...
rates
...
of
...
about
...
5.09
...
mL/L
...
and
...
2.01
...
mL/L,
...
respectively,
...
while
...
the
...
control
...
experiment
...
showed
...
a
...
rate
...
of
...
7.47
...
mL/L.
...
These
...
results
...
suggest
...
that
...
the
...
sand
...
inhibits
...
gas
...
removal,
...
rather
...
than
...
facilitating
...
it.
...
In
...
addition,
...
the
...
concentration
...
of
...
dissolved
...
oxygen
...
measured
...
at
...
each
...
of
...
the
...
four
...
ports
...
in
...
the
...
system
...
(tabulated
...
below)
...
support
...
the
...
notion
...
that
...
the
...
sand
...
filter
...
did
...
not
...
provide
...
a
...
suitable
...
mechanism
...
of
...
gas
...
removal,
...
as
...
the
...
measurements
...
indicated
...
higher
...
oxygen
...
concentrations
...
in
...
the
...
water
...
at
...
points
...
past
...
the
...
sand
...
filter.
...
Literature
...
concerning
...
bubble
...
formation
...
and
...
behavior
...
indicate
...
that
...
rough,
...
hydrophobic
...
surfaces
...
are
...
most
...
suitable
...
for
...
bubble
...
formation.
...
(See
...
"Fundamentals
...
of
...
Bubble
...
Formation
...
during
...
Coagulation
...
and
...
Sedimentation
...
Processes"
...
by
...
P.
...
Scardina
...
and
...
M.
...
Edwards
...
on
...
the
...
...
...
...
...
page.)
...
The
...
sand
...
filter
...
may
...
be
...
unsuitable
...
because
...
sand
...
is
...
not
...
hydrophobic.
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{anchor:Figure 1} {float:left|border=10px solid white}[!0804091509a.jpg|width="400", height="300"!|Aerator] h6. The aerator with four aeration stones {float} |
Concerning,
...
the
...
dissolved
...
oxygen
...
measurements,
...
the
...
results
...
indicate
...
that
...
the
...
aerator
...
is
...
able
...
to
...
supersaturate
...
the
...
water
...
with
...
15.5
...
mg/L
...
of
...
dissolved
...
oxygen.
...
This
...
is
...
less
...
than
...
the
...
theoretical
...
rate
...
18
...
mg/L.
...
Please
...
see
...
the
...
Table
...
1.
...
below
...
for
...
the
...
dissolved
...
oxygen
...
concentrations
...
and
...
click
...
...
for
...
more
...
details
...
and
...
subsequent
...
DO
...
measurements
...
in
...
the
...
absence
...
of
...
sand.
...
Also,
...
further
...
measurements
...
at
...
that
...
port
...
reveal
...
inconsistent
...
levels
...
of
...
gas
...
supersaturation.
...
This
...
inability
...
to
...
regulate
...
the
...
amount
...
of
...
dissolved
...
gas
...
in
...
the
...
influent
...
water
...
to
...
the
...
sand
...
filter
...
may
...
have
...
a
...
significant
...
impact
...
on
...
our
...
ability
...
to
...
run
...
controlled
...
experiments.
...
In
...
order
...
to
...
address
...
this
...
issue,
...
the
...
team
...
has
...
altered
...
the
...
pressurized
...
aerator
...
by
...
replacing
...
the
...
single
...
aeration
...
stone
...
with
...
a
...
junction
...
of
...
four
...
cylindrical
...
aeration
...
stones
...
that
...
would
...
displace
...
gas
...
into
...
the
...
water
...
in
...
finer
...
bubbles,
...
which
...
would
...
be
...
incorporated
...
into
...
solution
...
more
...
easily.
...
Table
...
1:
...
Dissolved
...
Oxygen
...
Concentrations
...
(DO)
...
at
...
sampling
...
ports
...
in
...
the
...
experimental
...
setup
...
with
...
a
...
sand
...
bed.
...
Sampling |
|---|
...
Port |
|---|
...
DO |
|---|
...
(mL/L), |
|---|
...
Probe |
|---|
...
1, |
|---|
...
Trial |
|---|
...
1 |
|---|
...
DO |
|---|
...
(mg/L), |
|---|
...
Probe |
|---|
...
1, |
|---|
...
Trial |
|---|
...
2 |
|---|
...
DO |
|---|
...
(mg/L), |
|---|
...
Probe |
|---|
...
2, |
|---|
...
Trial |
|---|
...
1 |
|---|
...
DO |
|---|
...
(mL/L), |
|---|
...
Probe |
|---|
...
2, |
|---|
...
Trial |
|---|
...
2 | |
|---|---|
Water Source | 9.8 |
...
10.2 |
...
8.7 |
...
12.1 |
...
Beyond |
...
Aerator |
...
15.5 |
...
14.2 |
...
11.8 |
...
15.2 |
...
Beyond |
...
Sand |
...
Filter |
...
17 | 16.3 |
...
11.9 |
...
15.3 |
...
Beyond |
...
Bubble |
...
Collector |
...
17.8 |
...
16.2 |
...
12.3 |
...
15.7 |
...
It
...
is
...
also
...
possible
...
that
...
the
...
bubble
...
collector,
...
which
...
is
...
used
...
to
...
measure
...
gas
...
removal,
...
may
...
not
...
be
...
effective
...
at
...
capturing
...
small
...
bubbles.
...
Although
...
we
...
had
...
initially
...
suspected
...
that
...
the
...
small
...
bubbles
...
traveling
...
through
...
the
...
system
...
originated
...
in
...
the
...
sand
...
filter,
...
we
...
are
...
now
...
unsure
...
whether
...
small
...
bubbles
...
formed
...
in
...
the
...
sand
...
filter
...
itself.
...
During
...
the
...
controlled
...
experiment,
...
we
...
observed
...
that
...
small
...
bubbles
...
were
...
present
...
throughout
...
the
...
system.
...
Because
...
of
...
this,
...
we
...
suspect
...
that
...
the
...
source
...
of
...
the
...
small
...
bubbles
...
is
...
a
...
component
...
other
...
than
...
the
...
sand
...
filter--perhaps
...
the
...
aerator.
...
Before
...
the
...
team
...
redesigns
...
the
...
bubble
...
collector,
...
we
...
plan
...
to
...
modify
...
the
...
flow
...
accumulator
...
so
...
that
...
any
...
small
...
bubbles
...
coming
...
from
...
the
...
aerator
...
will
...
be
...
collected
...
so
...
that
...
water
...
entering
...
the
...
sand
...
filter
...
is
...
free
...
of
...
bubbles.
...
If
...
small
...
bubbles
...
are
...
formed
...
in
...
the
...
filter
...
and
...
the
...
bubble
...
collector
...
must
...
be
...
redesigned
...
to
...
capture
...
these
...
bubbles,
...
a
...
new
...
design
...
for
...
the
...
bubble
...
collector
...
will
...
be
...
developed.