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hyperchlorination, because in thismethod, amalfunctionof the equipment
may cause a rapid recolonization of the pipes by
Legionella
spp. However, it is
pointed out that water that causes incrustation in the electrodes, as well as water
withpHvalues higher than8.0, whichcauses precipitationof copper, can reduce
the efficiency of this disinfection process thus limiting its use (AWT, 2003).
Cachafeiro
et al
. (2007) by reviewing the literature, concluded that: the
use of copper-silver ions is an effective method to control
Legionella
, but one
should have in mind that the eradication is not achieved by using just a single
method of disinfection. These authors recommend the use copper-silver
ionization with hot water to increase the efficiency of the disinfection process.
However, they point out that the levels of these two metals must be kept within
the limits recommended by the regulatory agencies and they propose more
studies to evaluate the economic viability and the efficiency in the long term.
Lin
et al
. (2011) highlight some reports accounting for the appearance of
strains of
Legionella pneumophila
that are resistant to the copper-silver ions in
water distribution systems in hospitals. But this problem can be solved with the
correct control of the concentration of these ions. Lin
et al
. (2001) also report
that hospitals that used hyperchlorination as control method of
Legionella
are now using copper-silver ionization, because of the corrosion problem.
Ultravioletlight
,withwavelengthbetween250and280nm,destroysbacteria,
duetotheproductionofthyminedimersintheDNAwhichsubsequentlyhinders
itsreplication(Liu
etal
.,1995,Lin
etal
.,1998,Franzin
etal
.,2002,Kim
etal
.,2002,
AWT, 2003). Muraca
et al
. (1987) demonstrated that at 25 °C the irradiation
with ultraviolet lamps (30000 µW∙s∙cm-2) causes a reduction in the population
of
Legionella
between 4 and 5 log cycles in 20 minutes. Triassi
et al
.(2006)
showed that by using the radiation with ultraviolet lamps (33000 µW∙s∙cm
-2
)
it is possible to control the presence of
Legionella
spp at the interior of a water
