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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
...
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
...
the
...
sodium
...
sulfite
...
solution.
...
The
...
beaker
...
was
...
emptied
...
and
...
refilled
...
with
...
water
...
from
...
the
...
next
...
sampling
...
port.
...
This
...
was
...
repeated
...
until
...
water
...
from
...
all
...
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),
...
water
...
temperature
...
dropped
...
to
...
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 |
|---|
{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
...
...
...
...
...
...
...
...
.
...
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 |
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.