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Experiment
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1:
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Replicate
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of
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the
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Previous
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Sand
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40
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Experiment
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Procedure:
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For
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this
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experiment,
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the
...
...
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for
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this
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set
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of
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experiments
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was
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followed
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using
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the
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following
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parameters:
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Sand
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Grain
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Size:
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Sand
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40
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(.42
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mm
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-
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.59
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mm)
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Sand
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Bed
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Depth:
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60
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cm
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Sand
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Bed
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Expansion:
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50%
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Aerator
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Air
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Pressure:
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100
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kPa
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Flow
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Rate
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, measured manually: 225 ml/min
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Results
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and
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Discussion
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The
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results
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from
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the
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experiment
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indicate
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that
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the
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amount
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of
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dissolved
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air
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removed
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in
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the
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bubble
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collector
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decreased
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after
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each
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of
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the
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data
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collection
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periods.
| Anchor | ||||
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| Wiki Markup |
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{anchor:Figure 1} {float:left|border=12px solid white}[!figure 1.14.png|width="487", height="292"!|Gas Removal Preliminary Graphs] {float} [ |
...
...
depicts
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the
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initial
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and
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final
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water
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level
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in
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the
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bubble
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collector
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during
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each
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of
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the
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data
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collection
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period
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("runs").
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Each
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run
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represents
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a
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time
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period
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during
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which
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the
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water
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level
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in
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bubble
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collector
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gradually
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sinks
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falls down
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from
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its
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maximum
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to
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the
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set
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minimum
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point.
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This
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period
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is
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represented
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on
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the
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graph
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when
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the
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line
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slants
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downward.
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Once
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the
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minimum
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water
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level
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is
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reached,
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the
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system
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has
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to
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refill
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with
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water
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in
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order
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to
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continue
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the
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runs.
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For
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this
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reason,
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the
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water
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outflow
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valve
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is
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closed
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until
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the
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water
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level
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reaches
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the
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set
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maximum
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point.
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This
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period
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is
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represented
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on
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the
...
graph
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by
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the
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vertical
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lines.
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More
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detailed
...
information
...
on
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the
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bubble
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collector
...
setup
...
can
...
be
...
found
...
here.
The initial data collection period was omitted from the analysis since because of the setup conditions the air might have been trapped inside the system. For the subsequent data collection periods, we calculated the content of gas removed per liter of water sent through the sand filter. We added fitted a line to each of the runs to see the rate of change of the water level inside the bubble collector when water runs through the sand filter. Figure 2. and Figure 3. show the linear fit line for the second data collection period, and more detailed graphs can also can be found here.
| Anchor | ||||
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| Wiki Markup |
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|Floating Flocs Summer 2009 Set-up]. The initial data collection period was omitted from the analysis since because of the setup conditions the air might have been trapped inside the system. For the subsequent data collection periods, we calculated the content of gas removed per liter of water sent through the sand filter. We added fitted a line to each of the runs to see the rate of change of the water level inside the bubble collector when water runs through the sand filter. [Figure 2.|Gas Removal Preliminary Graphs] and [Figure 3.|Gas Removal Preliminary Graphs] show the linear fit line for the second data collection period, and more detailed graphs can also can be found [here|Gas Removal Preliminary Graphs]. {anchor:Figure 2} {float:left|border=12px solid white}[!figure 2.08.png|width="485", height="310"!|Gas Removal Preliminary Graphs] {float} {anchor:Figure 3} |
| Anchor | ||||
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| Wiki Markup |
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{float:left|border=7px solid white}[!figure 3.07.png|width="464", height="308"!|Gas Removal Preliminary Graphs]
{float}
\\
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The
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value
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of
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the
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linear
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fit
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is
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very
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close
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to
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1,
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indicating
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that
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the
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data
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can
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be
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modeled
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accurately
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using
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a
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linear
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relationship.
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If
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we
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multiply
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the
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slope
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of
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the
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line
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by
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the
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cross
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sectional
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area
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of
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the
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bubble
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column,
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we
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get
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the
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rate
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of
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change
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in
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the
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volume
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of
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water
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with
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respect
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to
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time:
| Latex |
|---|
Then we divide the volume rate of change by the flow rate to find out how many milliliters of dissolved gas are removed per liter of water sent upwards through the sand filter:
| Latex |
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For these calculations we used following values:
- radius of the bubble collector = 1.9cm
- flowrate = 225 mL/min (measured manually)
The calculations for the amount of gas removed during each data collection periods gave us the results summarized in Table 1. and Figure 4.:
| Wiki Markup |
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\\ {latex} $$ \frac{\Delta Volume}{\Delta Time} = slope * \pi * r _{collector} ^2 $$ {latex} \\ Then we divide the volume rate of change by the flow rate to find out how many milliliters of dissolved gas are removed per liter of water sent upwards through the sand filter: \\ {latex} $$ \frac{mL\:gas\:removed}{L\:water\:treated} = \frac{\frac{\Delta Volume}{\Delta Time}}{Q_{water}} $$ {latex} \\ For these calculations we used following values: * radius of the bubble collector = 1.9cm * flowrate = 225 mL/min (measured manually) \\ The calculations for the amount of gas removed during each data collection periods gave us the results summarized in Table 1. and [Figure 4.|Gas Removal Preliminary Graphs]: {float:left|border=12px solid white|width="200"} h5. Table 1: Gas Removal vs. Collection Periods. ||Run||Slope (cm/min)||R ^2^ value||Dissolved Gas Removed (mL/L)|| |2|0.1013|.9948|5.0909| |3|0.0986|.9920|4.9397| |4|0.0861|.9933|4.3348| |5|0.0739|.9945|3.6795| |6|0.0659|.9921|3.2763| |7|0.0616|.9872|3.0747| {float} {anchor:Figure 4} |
| Anchor | ||||
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| Wiki Markup |
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{float:left|border=23px solid white}[!figure 4.04.png|width="457", height="292"!|Gas Removal Preliminary Graphs]
{float}
\\
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Data
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was
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recorded
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for
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Sand
...
40
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with
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each
...
of
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the
...
parameters
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specified
...
above.
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The
...
results
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of
...
the
...
experiment
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can
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be
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downloaded
...
...
in
...
the
...
form
...
of
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the
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Excel
...
sheet.
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The
...
content
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of
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the
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gas
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removed
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during
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the
...
second
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run,
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5.09
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mL/L,
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is
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very
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similar
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to
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the
...
result
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from
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the
...
...
...
...
done
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last
...
semester,
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when
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the
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measured
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content
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of
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gas
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removed
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was
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5.07
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mL/L.
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The
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fluidized
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bed
...
experiment
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involved
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the
...
same
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sand
...
parameters:
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Sand
...
40,
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depth
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=
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60cm,
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bed
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expansion
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=
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50%,
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aerator
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air
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pressure
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=
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100kPa,
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except
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for
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the
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flow
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rate,
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which
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was
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345
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mL/min.
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While
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the
...
data
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from
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the
...
second
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run
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are
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comparable,
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the
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data
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for
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each
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subsequent
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runs
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show
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gradual
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decrease
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in
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the
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content
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of
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air
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removed.
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These
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decreasing
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rates
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of
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gas
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removal
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probably
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resulted
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from
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a
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clogging
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problem
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in
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the
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sand
...
filter.
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Clogging
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in
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the
...
filter
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occurs
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because
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of
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the
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diameter
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of
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the
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sand
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column
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is
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relatively
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small.
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Large
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bubbles
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form
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in
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the
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sand
...
bed
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and
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push
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segments
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of
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sand
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up
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to
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the
...
top
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of
...
the
...
filter.
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While
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we
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did
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not
...
directly
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observe
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this
...
problem
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during
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the
...
experiment,
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sensor
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data
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collected
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through
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Process
...
Controller
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indicates
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that
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clogging
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occurred.
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Additionally,
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the
...
results
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can
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be
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compared
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with
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the
...
...
...
...
...
,
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which
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models
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the
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theoretical
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bubble
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formation
...
potential
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as
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a
...
function
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of
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the
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air
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pressure
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that
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the
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water
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equilibrated
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with
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prior
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to
...
returning
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to
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atmospheric
...
pressure.
| Anchor | ||||
|---|---|---|---|---|
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| Wiki Markup |
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{anchor:Figure 5} {float:left|border=12px solid white}[!Theoretical bubble formation potential.png|width="372", height="289"} !|GasTheoretical Removalbubble Preliminary Graphs]formation potential.png! h6. Figure 5: Theoretical bubble formation potential {float} |
The
...
model
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predicts
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the
...
theoretical
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bubble
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formation
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potential
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to
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be
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around
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18mL/L
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for
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water
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that
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has
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been
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previously
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exposed
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to
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1
...
atm
...
gage
...
pressure
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at
...
temperature
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of
...
25
...
C.
...
Since
...
our
...
data
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show
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the
...
removal
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of
...
only
...
5.09
...
mL/L
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of
...
the
...
air
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entrained
...
in
...
the
...
system,
...
it
...
is
...
probable
...
that
...
some
...
of
...
the
...
system
...
components
...
might
...
not
...
be
...
functioning
...
properly.
...
The
...
sand
...
filter
...
might
...
not
...
be
...
able
...
to
...
remove
...
all
...
the
...
bubbles
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coming
...
in.
...
If
...
the
...
bubbles
...
in
...
the
...
system
...
encounter
...
a
...
region
...
of
...
lower
...
pressure,
...
they
...
might
...
become
...
trapped
...
and
...
form
...
a
...
column
...
of
...
gas
...
entrained
...
inside.
...
Additionally,
...
bubbles
...
in
...
the
...
sand
...
filter
...
may
...
be
...
concentrated
...
on
...
the
...
fluid
...
surface
...
as
...
floats,
...
thus
...
creating
...
a
...
gas-liquid
...
interface.
...
It
...
is
...
also
...
possible
...
that
...
the
...
aerator
...
and
...
bubble
...
collector
...
might
...
not
...
be
...
working
...
properly.
...
It
...
might
...
be
...
necessary
...
to
...
measure
...
the
...
oxygen
...
concentration
...
at
...
various
...
points
...
in
...
the
...
system
...
to
...
see
...
what
...
might
...
contribute
...
to
...
the
...
lower
...
content
...
of
...
air
...
removed.
...
Conclusions
While the results collected were unexpected, the initial runs indicate a gas removal very similar to that found in the Spring 2009 experiment. Since conditions in the aerator were maintained throughout the experiment, it is likely that the new aerator works as needed. However, the decreasing gas removal found for each run is cause for concern. We plan to install a webcam at the top of the filter to observe any instances of clogging during the experiment.
While we attempt to find a permanent solution to the clogging problem, we will also determine a minimum expansion for which clogging does not occur in the sand column. Although obtaining a larger diameter sand column would probably fix the clogging problem, we hope to avoid that option since a wider sand column would require higher flow rates through the system. This would probably require significant upgrades to the plumbing in the system and would be too time-costly and inefficient, since higher flow rates would also decrease the residence time of water in the new aerator, which was installed specifically for greater residence time.