Chlorination
Introduction and Objectives
Chlorination is the final step in the treatment process. Chlorine disinfects the effluent, killing whatever pathogens may remain. AguaClara plants use a flow control module (FCM) to regulate chlorine dose (figure 1).
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h1. Chlorination h2. Introduction and Objectives Chlorination is the final step in the treatment process. Chlorine disinfects the effluent, killing whatever pathogens may remain. AguaClara plants use a [flow control module (FCM)| Flow Controller] to regulate chlorine dose (figure 1). {float:right|border=2px solid black|width=400px}!flow controller schematic.JPG|width=400px! h5. Figure 1: flow control module schematic {float} |
The
...
chlorine
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flow
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is
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driven
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by
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available
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head
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in
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the
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FCM
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and
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the
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dose
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is
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changed
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by
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increasing
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or
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decreasing
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this
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available
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head.
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Chlorine
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is
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added
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in
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the
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plant
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before
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water
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is
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sent
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to
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the
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distribution
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line.
...
The
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residual
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from
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this
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chlorine
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should
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guarantee
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protection
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from
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pathogens
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along
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the
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distribution
...
line.
...
In
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this
...
study,
...
the
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chlorine
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residual
...
was
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measured
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daily
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in
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the
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storage
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tank,
...
and
...
three
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houses
...
along
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the
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distribution
...
line.
...
Additionally,
...
samples
...
were
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taken
...
from
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the
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storage
...
tank
...
and
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the
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chlorine
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residual
...
was
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measured
...
in
...
them
...
over
...
time.
...
The
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flow
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rate
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in
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the
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chlorinator
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was
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measured
...
to
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make
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sure
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the
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FCM
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was
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delivering
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the
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expected
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dose.
...
Methods
Chlorine residual was monitored daily in four locations in the distribution system---
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The
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tank,
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the
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first
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house
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in
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the
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distribution
...
line,
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a
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house
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in
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the
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middle
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of
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the
...
line
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and
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the
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last
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house
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in
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the
...
line.
...
Chlorine
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residual
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was
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measured
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with
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a
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Pentair
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Pool
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Products™
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Pool
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and
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Spa
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Test
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Kit
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which
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used
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ortotolidine
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to
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detect
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chlorine.
...
However,
...
in
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should
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be
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noted
...
that
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the
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test
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is
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a
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fairly
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subjective
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colorimetric
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test
...
and
...
that
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the
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measurements
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were
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taken
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by
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three
...
different
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people.
...
Therefore
...
the
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results
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only
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show
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relative
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levels
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of
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chlorine
...
not
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exact
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amounts.
...
To
...
measure
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how
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long
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the
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chlorine
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residual
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lasts
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at
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different
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effluent
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turbidities
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water
...
samples
...
were
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taken
...
from
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the
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storage
...
tank
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and
...
then
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the
...
residual
...
was
...
measured.
...
The
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chlorine
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flow
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rate
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was
...
measured
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using
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the
...
same
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clear
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PVC
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piping
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used
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for
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the
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CDC
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(See
...
...
...
section).
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The
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actual
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flow
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rates
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were
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measured
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before
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and
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after
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cleaned
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the
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hosing
...
in
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the
...
FCM.
...
Each
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trial
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was
...
performed
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three
...
times
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consecutively
...
and
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the
...
average
...
of
...
these
...
trials
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was
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taken
...
to
...
be
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the
...
flow
...
rate.
Results and Discussion
Monitoring the chlorine residual along the distribution line was a good method of ensuring that that water was safe to drink. The residence time from the plant to the end of the distribution line depends on the demand on the system making it difficult to determine how long the chlorine residual lasts. Furthermore, samples were not taken at the same time each day at each location. More information about chlorine residual was gained from the samples taken from the tank. An effluent sample with turbidity of 26.49 NTU and an initial chlorine residual of 1.5 mg/L had measurable chlorine residual for fifteen and a half hours. At this point the residual was 0.3 mg/L. Effluent samples with less than 4 NTU turbidity and chlorine concentrations of 1.5 mg/L taken on different days contained detectable chlorine for over
The actual flow rate through the FCM was compared to the theoretical flow rate (figure 1).
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h2. Results and Discussion Monitoring the chlorine residual along the distribution line was a good method of ensuring that that water was safe to drink. The residence time from the plant to the end of the distribution line depends on the demand on the system making it difficult to determine how long the chlorine residual lasts. Furthermore, samples were not taken at the same time each day at each location. More information about chlorine residual was gained from the samples taken from the tank. An effluent sample with turbidity of 26.49 NTU and an initial chlorine residual of 1.5 mg/L had measurable chlorine residual for fifteen and a half hours. At this point the residual was 0.3 mg/L. Effluent samples with less than 4 NTU turbidity and chlorine concentrations of 1.5 mg/L taken on different days contained detectable chlorine for over The actual flow rate through the FCM was compared to the theoretical flow rate (figure 1). \\ {float:border=2px solid black|width=600px}!Chlorine1.gif|width=600px! h5. Figure 2 {float} |
The
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measured
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flow
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rates
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are
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probably
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different
...
because
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the
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hose
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was
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not
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always
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cleaned
...
before
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each
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trial
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was
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run.
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After
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cleaning
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the
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flow
...
rate
...
was
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close
...
to
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the
...
expected
...
trend
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(figure
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3).
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{float:border=2px solid black|width=600px}!Chlorine2.gif|width=600px! h5. Figure 3 {float} |
Initially
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the
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chlorine
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flow
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rate
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matches
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the
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expected
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flow
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rate,
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but
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as
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the
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available
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head
...
increases
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the
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flow
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rate
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is
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unable
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to
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reach
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the
...
expected
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maximum
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flow
...
rate.
...
This
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problem
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was
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also
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seen
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in
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the
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CDC
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tubing
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and
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can
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easily
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be
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fixed
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by
...
shortening
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the
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FCM
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tubing
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and
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therefore
...
decreasing
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the
...
head
...
loss
...
in
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the
...
system.
...
This
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data
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also
...
stresses
...
the
...
importance
...
of
...
cleaning
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the
...
system
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to
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obtain
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an
...
accurate
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chemical
...
dose.
...
Conclusions
The chlorine residual should last at least 15 hours if the turbidity is under 26 NTU. The turbidity going to the distribution system should always be below 10 NTU so this condition should always be met. The FCM needs to be kept clean to ensure the correct dose is being given. Additionally the FCM hosing should be shortened to decrease head loss and increase the maximum flow rate.