Reruns of the Previous Fluidized Bed Experiments
Parameters:
For both Experiment 1 and Experiment 2, the general procedure had been followed using values for parameters as listed and compared below:
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h1. Experiments 1 and 2 - Replicates of the Previous Fluidized Bed Experiments h2. Parameters: For both Experiment 1 and Experiment 2, the [general procedure|FF Procedure for Evaluation of Previous Experiments] had been followed using values for parameters as listed and compared below: {float:left|border=12px solid white|width="200"} h5. Table 1: Comparison of Parameters Used. ||Parameters:||Experiment 1||Experiment 2||Control Experiment|| |Sand Grain Type|Sand 40|Sand 30|No Sand| |Sand Grain Diameter|0.42 mm - 0.59 mm|0.59 mm - 0.84 mm|-| |Sand Bed Depth|60 cm|60 cm|-| |Sand Bed Expansion|50%|50%|-| |Aerator Air Pressure|100 KPa|100 KPa|100 KPa| |Flow Rate|225 mL/min|485 mL/min|530 mL/min| {float} \\ h2. Results and Discussion: All three experiments were run for more than ten hours, during which time several data collection periods |
Results and Discussion:
All three experiments were run for more than ten hours, during which time several data collection periods ("runs")
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were
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completed.
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The
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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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behaves
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like
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a
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periodic
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function.
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Each
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period
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represents
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a
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specific
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time
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interval
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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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the
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bubble
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collector
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gradually
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falls
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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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In
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Figure
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1.
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and
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Figure
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2.,
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this
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period
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is
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represented
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by
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each
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of
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the
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slanting
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lines
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on
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the
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graph.
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As
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soon
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as
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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
...
reached,
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the
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bubble
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collector
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refills
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with
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water
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to
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begin
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the
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next
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run.
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For
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this
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reason,
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at
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the
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beginning
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of
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each
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run,
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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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These
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refilling
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periods
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are
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represented
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on
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the
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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
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information
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on
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the
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bubble
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collector
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setup
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can
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be
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found
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here.
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|Floating Flocs Summer 2009 Set-up]. {anchor:Figure 1} {float:left|border=10px solid white}[!figure 1.02.png|width="440", height="312"!|Gas Removal Preliminary Graphs] {float} {anchor:Figure |
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2} {float:left|border=15px solid white}[!figure 2.02.png|width="432", height="307"!|Gas Removal Preliminary Graphs] {float} \\ |
Once
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the
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change
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in
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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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was
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recorded,
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we
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added
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a
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linear
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fit
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line
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to
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each
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of
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the
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runs
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to
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see
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the
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rate
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of
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change
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of
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the
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water
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level
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inside
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the
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bubble
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collector
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with
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respect
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to
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time.
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Figures
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3.
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and
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4.
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show
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the
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linear
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fit
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line
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for
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the
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second
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data
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collection
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period
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in
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both
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experiments,
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and
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more
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detailed
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graphs
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can
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also
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can
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be
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found
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here.
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|Gas Removal Preliminary Graphs]. {anchor:Figure 3} {float:left|border=15px solid white}[!figure 3.04.png|width="418", height="252"!|Gas Removal Preliminary Graphs] {float} {anchor:Figure 4} |
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{float:left|border=12px solid white}[!figure 4.02.png|width="404", height="254"!|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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Once
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the
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slope
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of
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the
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fitted
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line
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was
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known,
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we
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calculated
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the
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content
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of
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gas
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removed
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per
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liter
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of
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water
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sent
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through
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the
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sand
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filter
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using
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the
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formulas:
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\\ {latex} $$ \frac{\Delta Volume}{\Delta Time} = slope * \pi * r _{collector} ^2 $$ { |
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} \\ {latex} $$ \frac{mL\:gas\:removed}{L\:water\:treated} = \frac{\frac{\Delta Volume}{\Delta Time}}{Q_{water}} $$ {latex} \\ where the radius of the bubble column was |
where the radius of the bubble column was 1.9
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cm.
The calculations for the amount of gas removed during each data collection periods gave us the results summarized in Tables 2 and 3 below:
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\\ \\ The calculations for the amount of gas removed during each data collection periods gave us the results summarized in Tables 2 and 3 below: {float:left|border=12px solid white|width="200"} h5. Table 2: Gas Removal vs. Collection Periods; Experiment 1. ||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} |
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{float:left|border=12px solid white|width="200"}
h5. Table 3: Gas Removal vs. Collection Periods; Experiment 2.
||Run||Slope (cm/min)||R ^2^ value||Dissolved Gas Removed (mL/L)||
|2|0.0854|.9944|1.9970|
|3|0.0856|.9482|2.0017|
|4|0.0847|.9952|1.9806|
{float}
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{anchor:Figure 5} |
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{float:left|border=12px solid white}[!figure 5.04.png|width="382", height="446"!|Gas Removal Preliminary Graphs] {float} \\ |
For
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further
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reference,
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please
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download
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the
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experimental
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data
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logs
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from
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,
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,
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and
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.
The data from Experiment 1 is very similar to the results obtained last semester, when the measured content of gas removed was 5.07 mL/L. Yet the data log revealed a gradual decrease in the gas removal rate for each of the subsequent runs. It is likely that this resulted from a clogging problem in the sand filter. The believed cause of clogging in the sand filter is the relatively small diameter of the sand column. Large bubbles can form in the sand bed and push segments of sand up to the top of the filter. While we did not directly observe this problem during the experiment, sensor data collected through Process Controller suggests that clogging might have occurred.
Unlike in Experiment 1, the data from Experiment 2 shows consistent gas removal rate for each run. The majority of the experiment monitored visually and no clogging was observed. While the results were very consistent, the gas removal rate was still a bit lower than the results obtained last semester of 3.23 mL/L. The cause of the difference in results might be the experimental setup, which has been modified since last semester. For further observation, we measured the dissolved oxygen content at three sampling points in the system. More detailed information can be found here.
Additionally, these experimental results may be modeled as gas removal efficiency when subjected to two different sand grain sizes. Data suggests that the sand with larger media diameter might be less effective at gas removal. Particles with larger diameter have relatively lower surface area to volume ratio and thus provide less extra surface area to which the bubbles can adhere to in the sand column. Although the media size is just one of the factors that affect the gas removal rate, the results indicate that perhaps using particles with higher surface area to volume ratio might further optimize the conditions for dissolved air removal and thus facilitate the process under certain conditions.
The control experiment data showed that more amount of dissolved gas was removed in the absence of sand (7.47 mL/L vs. 5.09 mL/L for Sand 40 and 1.99 mL/L for Sand 30). As a result, sand might be inhibiting the gas removal as opposed to helping in the process.