1. GENERAL
The disinfection of potable water, swimming pool water and industrial water is usually
achieved by the addition of either chlorine, chlorine dioxide, sodium hypochlorite,
anorganic chlorine compounds or in combination with ozone.
It is very important to dose these disinfectants properly in order to achieve the correct
residual. An insufficient residual of the disinfectant may result in poor disinfection,
whereas an excessive residual may affect the taste of the water unfavourably or cause
corrosion in the water lines.
The DEPOLOX 4 residual analyser may be used for the continuous measurement of
disinfectant residuals such as chlorine, chlorine dioxide or ozone.
With additional equipment the dosage of these disinfectants may be controlled and
recorded.
The unit may also be used to check water which must not contain any disinfectants
(e.g. to check that no ozone is present after the water has passed through a
dechlorination filter).
2. DISINFECTANTS IN WATER - LIMIT VALUES
2.1 CHLORINE (Cl2)
According to current German regulations, potable water must not contain more than
0.3mg/l of effective chlorine. This amount may be increased temporarily up to 0.6mg/l
if required for sufficient disinfection.
A further requirement is that potable water (and water used by the food processing
industry) disinfected with chlorine shall contain at least 0.1 mg/l of free chlorine after
chlorination.
Processed swimming pool water (after flocculation, filtering and chlorination) is required
to contain 0.3...0.6 mg/l of free chlorine in every part of the swimming pool. The water
leaving the pool shall contain at least 0.3 mg/l of free and effective chlorine. If a
treatment with ozone is included in the process, the content of free chlorine in the water
shall be 0.2...0.5 mg/l.
NOTE!
The presence of chlorisocyanurates (chlorine stabilisers) will strongly impair the
measurement of chlorine residual. These chemicals, available in the form of
granules or pills, are not approved for use in swimming pool water and must not
be used in chlorine residual controlled systems.
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