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Calcium
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Hypochlorite
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Experiments
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Introduction
In Honduras,
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a
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Calcium
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Hypochlorite
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solution
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is
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used
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in
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the
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Agua
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Clara
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flow
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controllers
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to
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chlorinate
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the
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drinking
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water.
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Unfortunately,
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due
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to
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the
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precipitation
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of
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calcium
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carbonate,
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the
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system
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clogs,
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which
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leads
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to
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large
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decrease
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in
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the
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flow
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rate
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(and
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thus
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dosing)
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of
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the
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chlorinating
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solution.
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The
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goal
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of
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these
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experiments
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were
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to
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find
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the
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contributing
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factors
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to
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failure
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(significantly
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decreased
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flow
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rate)
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by
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modeling
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a
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hypochlorinator
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in
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use
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in
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Honduras.
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Procedure
The experimental model is displayed below. The five gallon stock tank consists of a calcium hypochlorite solution at a concentration of 17.435 g/L.
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After
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mixing
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the
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solution,
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it
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was
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allowed
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to
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settle
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for
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approximately
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half
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an
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hour.
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In
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Honduras,
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the
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stock
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tank
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consists
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of
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a
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55
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gallon
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tank
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that
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runs
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for
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approximately
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three
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days.
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In
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order
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to
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model
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this,
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the
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stock
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tank
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was
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run
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at
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8
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hour
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intervals
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and
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refilled
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when
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it
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was
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depleted,
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and
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then
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run
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again.
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The
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target
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flow
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rate
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used
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48.1
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mL/min,
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the
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same
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as
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55
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gallons/
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3
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days.
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Overnight,
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the
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flow
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rate
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was
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to
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be
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slowed
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down
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to
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approximately
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a
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third
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of
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the
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flow
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rate
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by
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decreasing
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the
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change
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in
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head
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by
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a
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third.
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It
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would
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be
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evident
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that
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the
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system
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had
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reached
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failure
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when
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the
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flow
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rate
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had
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decreased
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significantly.
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Steps
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would
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then
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be
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taken
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to
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determine
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which
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portion
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had
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failed.
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Experimental Set Up
Results
For the first several days of the experiment, the flow rate fluctuated slightly, and no significant drop had occurred. By Thursday, the fifth day of the experiment, we experienced a drastic drop in the flow rate. On Friday, another drastic drop had occurred. A simplified chart of the flow rates, excluding many of the data points, is included below. A full chart of the flow rates is attached to this page.
Simplified Flowrate Chart
| Wiki Markup |
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{excel:file=^Flow Rates simplified.xls |
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|formatCell=true} |
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Conclusion
The flow rate had significantly decreased by day 6 of the experiment. By this point, approximately 20 gallons of the solution had run through the system. It was determined that the float valve was what had clogged first, because the head in the constant head tank had been decreasing. Furthermore the flow of solution into the constant head tank had decreased significantly, despite the fact that the tube leading from the stock tank was completely full with water. Because of this finding, we now have a more firm idea of what part of the system is first to fail and would require cleaning earlier than the rest of the system. Finally, it has not yet been determined whether failure is due to the volume of solution flowing through the system, velocity of the solution or simply the amount of time that the solution had spent in the flow controller. An efficient cleaning process has not been properly defined, due to the lack of time to complete the experiment. This will be one of the main focuses for this experiment when it is continued in the Fall.