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...
Dissolved
...
Oxygen
...
Measurements
...
According
...
to
...
...
...
...
...
...
,
...
bubble
...
formation
...
potential
...
in
...
the
...
water
...
should
...
be
...
18
...
mL/L.
...
Our
...
measured
...
values
...
for
...
gas
...
removal
...
were
...
5.09
...
mL/L
...
and
...
1.99
...
mL/L
...
for
...
Sand
...
40
...
and
...
Sand
...
30,
...
respectively.
...
Because
...
measured
...
gas
...
removal
...
was
...
so
...
much
...
lower
...
than
...
the
...
theoretical
...
value,
...
we
...
twice
...
measured
...
the
...
dissolved
...
concentration
...
at
...
each
...
sampling
...
port
...
to
...
determine
...
which
...
of
...
the
...
components
...
was
...
not
...
functioning
...
effectively.
...
Procedure
Sampling Points:
...
Water
...
Source,
...
Aerator
...
Effluent,
...
Sand
...
Filter
...
Effluent,
...
Bubble
...
Collector
...
Effluent
...
Dissolved
...
oxygen
...
probes
...
were
...
used
...
to
...
measure
...
the
...
concentration
...
of
...
dissolved
...
oxygen
...
in
...
samples
...
of
...
water
...
taken
...
from
...
the
...
water
...
source
...
and
...
effluents
...
from
...
the
...
aerator,
...
the
...
sand
...
filter,
...
and
...
the
...
bubble
...
collector.
...
Two
...
different
...
probes
...
were
...
used
...
in
...
samples
...
from
...
each
...
point
...
to
...
confirm
...
results.
...
After
...
each
...
probe
...
was
...
assembled,
...
it
...
was
...
placed
...
in
...
a
...
solution
...
of
...
sodium
...
sulfite
...
to
...
ensure
...
a
...
zero
...
reading.
...
Both
...
probes
...
we
...
used
...
accurately
...
read
...
the
...
dissolved
...
oxygen
...
concentration
...
in
...
the
...
sodium
...
sulfite
...
as
...
"0".
...
To
...
further
...
ensure
...
the
...
probes'
...
accuracy,
...
they
...
separately
...
were
...
placed
...
in
...
a
...
sample
...
of
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tap
...
water,
...
which
...
should
...
have
...
a
...
dissolved
...
oxygen
...
content
...
near
...
8
...
mg/L.
...
Though
...
the
...
readings
...
were
...
noisy,
...
both
...
probes
...
read
...
that
...
the
...
dissolved
...
oxygen
...
concentration
...
in
...
the
...
tap
...
water
...
was
...
within
...
0.5
...
mg/L
...
of
...
8
...
mg/L.
...
In
...
a
...
large
...
beaker,
...
water
...
was
...
collected
...
from
...
a
...
sampling
...
port
...
at
...
the
...
first
...
point,
...
just
...
beyond
...
the
...
water
...
source.
...
The
...
probe
...
was
...
inserted
...
near
...
the
...
center
...
of
...
the
...
water
...
sample
...
and
...
kept
...
stable
...
with
...
a
...
ring
...
stand.
...
After
...
the
...
probe
...
membrane
...
came
...
in
...
equilibrium
...
with
...
the
...
water,
...
the
...
dissolved
...
oxygen
...
reading
...
was
...
recorded,
...
and
...
the
...
probe
...
was
...
returned
...
to
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the
...
sodium
...
sulfite
...
solution.
...
The
...
beaker
...
was
...
emptied
...
and
...
refilled
...
with
...
water
...
from
...
the
...
next
...
sampling
...
port.
...
This
...
was
...
repeated
...
until
...
water
...
from
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all
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four
...
sampling
...
ports
...
had
...
been
...
tested
...
with
...
one
...
probe.
...
For
...
the
...
measurements
...
taken
...
with
...
the
...
sand
...
filter
...
in
...
place,
...
the
...
process
...
was
...
repeated
...
with
...
Probe
...
2.
...
With
...
the
...
sand
...
filter
...
in
...
place,
...
water
...
temperature
...
remained
...
at
...
20.8
...
°C
...
while
...
measurements
...
with
...
Probe
...
1
...
were
...
taken.
...
We
...
encountered
...
a
...
problem
...
while
...
using
...
Probe
...
2.
...
The
...
system
...
that
...
controls
...
water
...
temperature
...
was
...
temporarily
...
out
...
of
...
order,
...
and
...
we
...
began
...
measurements
...
with
...
the
...
source
...
water
...
temperature
...
at
...
about
...
33
...
°C.
...
As
...
we
...
continued
...
measurements
...
(from
...
the
...
sampling
...
port
...
just
...
beyond
...
the
...
water
...
source
...
down
...
the
...
line),
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water
...
temperature
...
dropped
...
to
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21
...
°C.
...
Measurements
...
were
...
taken
...
with
...
Probe
...
1
...
after
...
the
...
system
...
had
...
been
...
running
...
for
...
several
...
hours;
...
for
...
Probe
...
2,
...
the
...
system
...
had
...
been
...
running
...
for
...
about
...
45
...
minutes
...
when
...
measurement
...
began.
...
In
...
the
...
absence
...
of
...
sand,
...
water
...
temperature
...
stayed
...
at
...
21.4
...
°C
...
during
...
the
...
experiment.
...
The
...
system
...
had
...
been
...
running
...
for
...
several
...
hours
...
prior
...
to
...
taking
...
DO
...
measurements.
...
This
...
ensured
...
that
...
the
...
water
...
was
...
supersaturated
...
throughout
...
the
...
system.
Results and Discussion
The results were very unexpected. Table 1. shows the first set of DO measurements taken after the Sand 40 experiment was performed. Water temperature was 20.8 °C when Probe 1 was used. Water temperature varied from about 33 to 21 °C while Probe 2 was used to measure dissolved oxygen concentrations, which may have affected the measured dissolved oxygen concentrations for the first trial of the second probe.
| Wiki Markup |
|---|
h2. Results and Discussion The results were very unexpected. Table 1. shows the first set of DO measurements taken after the Sand 40 experiment was performed. Water temperature was 20.8 °C when Probe 1 was used. Water temperature varied from about 33 to 21 °C while Probe 2 was used to measure dissolved oxygen concentrations, which may have affected the measured dissolved oxygen concentrations for the first trial of the second probe. {float:left|border=12px solid white|width="200"} h5. Table 1.: Dissolved Oxygen Concentrations (DO) Measurements with Sand. || Sampling Port || DO (mL/L), Probe 1, Trial 1 || DO (mL/L), Probe 1, Trial 2 || DO (mL/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 | {float} |
Visual
...
observation
...
of
...
the
...
samples
...
taken
...
support
...
the
...
dissolved
...
oxygen
...
concentrations
...
measured.
...
The
...
samples
...
were
...
very
...
cloudy
...
with
...
small
...
bubbles,
...
indicative
...
of
...
supersaturation.
...
If
...
the
...
system
...
were
...
working
...
properly,
...
the
...
dissolved
...
oxygen
...
concentration
...
would
...
decrease
...
from
...
the
...
aerator
...
to
...
the
...
bubble
...
collector,
...
and
...
the
...
water
...
taken
...
from
...
the
...
sand
...
filter
...
effluent
...
and
...
the
...
bubble
...
collector
...
effluent
...
would
...
contain
...
large
...
bubbles.
...
We
...
observed
...
that
...
no
...
large
...
bubbles
...
were
...
present
...
in
...
either
...
sample
...
but
...
very
...
small
...
bubbles
...
were
...
abundant
...
in
...
both.
...
These
...
results
...
indicated
...
a
...
problem
...
with
...
the
...
setup
...
or
...
the
...
fluidized
...
bed
...
method.
...
Pressure
...
measurements
...
were
...
taken
...
and
...
the
...
head
...
loss
...
through
...
the
...
sand
...
filter
...
was
...
calculated
...
to
...
ensure
...
that
...
large
...
head
...
loss
...
through
...
the
...
system
...
in
...
combination
...
with
...
pressure
...
build
...
up
...
in
...
the
...
setup
...
was
...
not
...
resulting
...
in
...
tiny
...
bubbles
...
being
...
reincorporated
...
into
...
solution.
...
The
...
results
...
of
...
these
...
calculations
...
can
...
be
...
found
...
in
...
the
...
...
...
...
...
...
...
file.
...
The
...
measured
...
head
...
loss
...
through
...
the
...
system
...
seemed
...
to
...
match
...
up
...
fairly
...
well
...
to
...
theoretical
...
expectations.
...
In
...
order
...
to
...
assess
...
the
...
effectiveness
...
of
...
the
...
fluidized
...
bed
...
method,
...
a
...
control
...
experiment
...
was
...
performed
...
without
...
sand
...
and
...
dissolved
...
oxygen
...
measurements
...
were
...
taken
...
at
...
the
...
end
...
of
...
the
...
experiment
...
before
...
stopping
...
the
...
setup.
...
The
...
results
...
can
...
be
...
found
...
below
...
in
...
Table
...
2.
...
Juxtaposition
...
of
...
the
...
results
...
from
...
Table
...
1
...
and
...
Table
...
2
...
indicate
...
that
...
the
...
fluidized
...
bed
...
method
...
was
...
not
...
effective
...
at
...
removing
...
gas,
...
because
...
the
...
presence
...
of
...
sand
...
did
...
not
...
significantly
...
decrease
...
the
...
dissolved
...
oxygen
...
concentration
...
in
...
the
...
water.
| Wiki Markup |
|---|
{float:left|border=12px solid white|width="200"} h5. Table 2.: Dissolved Oxygen Concentrations (DO) Measurements in the Absence of Sand ||Trial||Flowrate (ml/min)|| Source water DO (mg/L)||After Aerator DO (mg/L)||After Sand Filter DO (mg/L)||After Bubble Collector DO (mg/L)||Temperature (C)|| |1|530|12.0|15.3|15.6|16.1|21.4| |2|530|11.6|16.0|16.0|16.0|21.4| |3|530|11.4|16.0|16.0|15.9|21.4| {float} \\ \\ h2. Conclusions The DO measurements confirm the results from the Control Experiment where it was shown that the sand is inhibiting the process of gas removal. DO measurements taken from various sampling points indicate that there is only a slight increase in the DO concentration as the water flows from the sand filter through aerator to the bubble collector. This might suggest that the bubble collector is collecting excess gas coming from the aerator. |
Conclusions
The DO measurements confirm the results from the Control Experiment where it was shown that the sand is inhibiting the process of gas removal. DO measurements taken from various sampling points indicate that there is only a slight increase in the DO concentration as the water flows from the sand filter through aerator to the bubble collector. This might suggest that the bubble collector is collecting excess gas coming from the aerator.