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).
| Wiki Markup |
|---|
| Wiki Markup |
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=300px400px}!flowcontrollerschematicflow controller schematic.JPG|width=240px400px! h5. Figure 1: flow control module schematic {float} |
The
...
chlorine
...
flow
...
is
...
driven
...
by
...
available
...
head
...
in
...
the
...
FCM
...
and
...
the
...
dose
...
is
...
changed
...
by
...
increasing
...
or
...
decreasing
...
this
...
available
...
head.
...
Chlorine
...
is
...
added
...
in
...
the
...
plant
...
before
...
water
...
is
...
sent
...
to
...
the
...
distribution
...
line.
...
The
...
residual
...
from
...
this
...
chlorine
...
should
...
guarantee
...
protection
...
from
...
pathogens
...
along
...
the
...
distribution
...
line.
...
In
...
this
...
study,
...
the
...
chlorine
...
residual
...
was
...
measured
...
daily
...
in
...
the
...
storage
...
tank,
...
and
...
three
...
houses
...
along
...
the
...
distribution
...
line.
...
Additionally,
...
samples
...
were
...
taken
...
from
...
the
...
storage
...
tank
...
and
...
the
...
chlorine
...
residual
...
was
...
measured
...
in
...
them
...
over
...
time.
...
The
...
flow
...
rate
...
in
...
the
...
chlorinator
...
was
...
measured
...
to
...
make
...
sure
...
the
...
FCM
...
was
...
delivering
...
the
...
expected
...
dose.
Methods
Chlorine residual was monitored daily in four locations in the distribution system--- The tank, the first house in the distribution line, a house in the middle of the line and the last house in the line. Chlorine residual was measured with a Pentair Pool Products™ Pool and Spa Test Kit which used ortotolidine to detect chlorine. However, in should be noted that the test is a fairly subjective colorimetric test and that the measurements were taken by three different people. Therefore the results only show relative levels of chlorine not exact amounts. To measure how long the chlorine residual lasts at different effluent turbidities water samples were taken from the storage tank and then the residual was measured.
The chlorine flow rate was measured using the same clear PVC piping used for the CDC (See CDC methods section). The actual flow rates were measured before and after cleaned the hosing in the FCM. Each trial was performed three times consecutively and the average of these trials was taken to be 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).
| Wiki Markup |
|---|
h2. Methods Chlorine residual was monitored daily in four locations in the distribution system. The tank, the first house in the distribution line, a house in the middle of the line and the last house in the line. Chlorine residual was measured with a Pentair Pool Products™ Pool and Spa Test Kit which used ortotolidine to detect chlorine. However, in should be noted that the test is a fairly subjective colorimetric test and that the measurements were taken by three different people. Therefore the results only show relative levels of chlorine not exact amounts. To measure how long the chlorine residual lasts at different effluent turbidities. Water samples were taken from the storage tank and then the residual was measured. The chlorine flow rate was measured using the same clear PVC piping used for the CDC (See [CDC methods| Cuatro Communidades Chemical Dose Controller] section). The actual flow rates were measured before and after cleaned the hosing in the FCM. Each trial was performed three times consecutively and the average of these trials was taken to be the flow rate. 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
...
measured
...
flow
...
rates
...
are
...
probably
...
different
...
because
...
the
...
hose
...
was
...
not
...
always
...
cleaned
...
before
...
each
...
trial
...
was
...
run.
...
After
...
cleaning
...
the
...
flow
...
rate
...
was
...
close
...
to
...
the
...
expected
...
trend
...
(figure
...
3).
| Wiki Markup |
|---|
{float:border=2px solid black|width=600px}!Chlorine2.gif|width=600px! h5. Figure 3 {float} |
Initially
...
the
...
chlorine
...
flow
...
rate
...
matches
...
the
...
expected
...
flow
...
rate,
...
but
...
as
...
the
...
available
...
head
...
increases
...
the
...
flow
...
rate
...
is
...
unable
...
to
...
reach
...
the
...
expected
...
maximum
...
flow
...
rate.
...
This
...
problem
...
was
...
also
...
seen
...
in
...
the
...
CDC
...
tubing
...
and
...
can
...
easily
...
be
...
fixed
...
by
...
shortening
...
the
...
FCM
...
tubing
...
and
...
therefore
...
decreasing
...
the
...
head
...
loss
...
in
...
the
...
system.
...
This
...
data
...
also
...
stresses
...
the
...
importance
...
of
...
cleaning
...
the
...
system
...
to
...
obtain
...
an
...
accurate
...
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.