Disinfection means destruction or inactivation of pathogenic micro-organisms that
can be achieved by UV irradiation at wave lengths
between 200 and 300 nm. UV radiation proves to be
a fast, reliable, effective, economical and environmentally
friendly disinfection method being successfully applied
world-wide for several years.
Micro-organisms possess a repair mechanism
meaning that even after destruction
of their DNA (desoxyribonucleic acid) they
are capable of reactivation. This process
can be influenced by light and time
expressed in terms of photo-reactivation.
Medium pressure lamps, which not only
destroy the DNA with their range of wave
length but also the cell components such
as proteins and enzymes, are preferable in
these cases. Reactivation is prevented.
SELECTION OF THE UV SYSTEM
The following criteria dictate the selection
of the appropriate UV system:
- Type of micro-organisms to be destroyed
- Water flow rate to be treated
- Type of lamps (low pressure or medium pressure)
- UV dose (= UV-fluence; energy absorbed by micro-
organisms)
- Water temperature
- Requested rate of disinfection
- Transparency of UV light in a liquid, expressed
by the following parameters:
- Transmission T10, T50,
T100 or
- SWC Spectral Weakening Coefficient or
- SAC Spectral Absorption Coefficient
In addition, the water to be treated needs to meet specific requirements in order
to achieve maximum disinfection. Chemical-physical
influences such as turbidity, water hardness, the
level of suspended solids, iron, manganese as well
as humic acid are important. The different substances
in the water reduce the transmission value and may
foul the UV system or even lead to deposits on the
quartz sleeves.
Siemens Water Technologies specialists will be pleased
to advise you concerning other influencing factors
to be considered depending on the respective applications.
Next:  Wide disinfection
spectrum through different types of lamps
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