Disinfection - Bayrol PoolManager Chlorine User Manual

11.2

Disinfection

Alternatively, there are three water disinfection variations available for
PoolManager :
®
Disinfection with active chlorine
(Measurement and control of redox potential)
Disinfection with active bromine
(Measurement and control of redox potential)
Disinfection with active oxygen
(Automatic dosing with temperature compensation)
11.2.1 PoolManager PRO
®
INFO
This section applies for the PoolManager
model only.
For the PoolManager ® PRO, disinfection can be performed with active
chlorine or active bromine. Both of these disinfectants can be
measured and controlled with PoolManager
measuring cell.
PoolManager ® PRO's potentiostatic chlorine measurement directly
records the portion of free chlorine / bromine in the pool that is
effective for disinfection. This is the hypochlorous acid HOCl.
Depending on pH value, only a certain portion of free chlorine is
present as HOCl; please refer to the section Correlation pH value and
disinfection.
11.2.2 Redox value
(Disinfection with chlorine or bromine)
INFO
This section applies for the models PoolManager
and PoolManager ® Br only.
The redox value of the pool water represents an electric potential
(electrical voltage) that can be measured using a corresponding
electrode (redox electrode).
The redox potential is a measure for the water's oxidation potential,
and therefore for the current disinfection effectiveness.
The redox value is a sum parameter that can be influenced by
numerous substances in the pool water.
Oxidizing substances (disinfectants) raise the redox value

Hypochlorous acid HOCl for disinfection with active chlorine

Hypobromous acid HOBr for disinfection with active bromine
Reducing substances (contaminants) lower the redox value

Inorganic and organic contaminants

Chloramines, oils, carbamide, sweat, germs, bacteria, algae,
leaves, etc.
Due to these numerous influences, it is not possible to determine the
exact chlorine / bromine level in the pool directly from the redox value
measured. It is, however, possible to set the desired chlorine / bromine
value in the pool and then to calculate the associated redox value.
IMPORTANT NOTICE!
Determining the correct redox value
For different pools with the same chlorine value or
bromine value, the redox value may be widely different.
For example, a chlorine value of 0.8 mg/l can lead to a
redox value of 720 mV in one pool, while in another
pool, it can lead to a redox value of 780 mV.
 Do not rely on values seen in the past. Rather,
determine the correct redox value for each pool
individually.
The determined redox value for the desired chlorine / bromine value is
configured as a setpoint in PoolManager
that the redox value remains consistently on level with the configured
setpoint.
As long as there are no significant changes in other influential
variables, the consistent redox value simultaneously provides for a
constant chlorine / bromine level in the pool, thereby ensuring reliable
disinfection.
11.2.3
PRO
®
The basic prerequisite for reliable and stable disinfection with chlorine
® PRO's potentiostatic
and bromine is a constant and optimally adjusted pH value in the pool.
There are two significant reasons for this:
For high pH values over 7.5, the proportion of free chlorine present as
hypochlorous acid (HOCl) drops dramatically. Since, however, only
hypochlorous acid is effective for disinfection, disinfection
effectiveness reduces in the same dimension. Sufficient disinfection is
no longer ensured.
Free chlorine measurement, and also the redox signal measured, are
not dependent upon the level of all available free chlorine, but rather
influenced only by the hypochlorous acid, which is effective for
disinfection. If, however, the proportion of hypochlorous acid changes
due to a fluctuating pH value, then that will necessarily lead to a
® Cl
fluctuating redox value. Stable and reliable disinfection is then no
longer possible.
The so-called dissociation curve shows the correlation between pH
value and the proportion of hypochlorous acid HOCl among all free
chlorine. At a pH of 6.5, ca. 95% of the free chlorine is present as
HOCl. At a pH of 7.8, however, that number is only 30%.
If control measurements are performed using the DPD method, then it
is important to know that the DPD measurement is always performed
at a pH value of ca. 6.2. That value is attained with an integrated pH
buffer in the DPD reagents. Thus, a DPD measurement always
measures all free chlorine independently of the actual pH value in the
pool. Therefore, a DPD measurement may not be significant for the
real disinfection effectiveness, especially, if pH is above ca. 7.5.
® . The control system ensures
Correlation pH value and disinfection
INFO
This section applies for the models PoolManager
PoolManager ® Br and PoolManager
® Cl,
® PRO only.
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