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high, can be mentioned: there may be precipitation of salts that cause temporary
hardness to the water and the consequent formation of scales in the surface;
people can suffer burns if touching the surfaces being treated by this method; the
thermal process ensures only a temporary disinfection; it is difficult to guarantee
full effectiveness over the entire surface that is being treated, because when the
temperatureof thewater is reducedtovaluesbelow50°C, therecolonizationof the
surface can occur again within weeks or months (Triassi
et al
., 2006, AWT, 2003,
Sabria andYu, 2002). Triassi
et al
. (2002) verified that awater distribution system
submitted to a treatment withwater at 65 °C for 3 hours presented recolonization
of
Legionella
after one month from the application of the thermal treatment.
Another point that several authors point out in the use of hot water rinsing is
the fact that the eradication of
Legionella
fromwater distribution systems is only
achieved by keeping a continuous flush of the water, at temperature above 60 °C,
along the entire system, including the farthest point fromthehotwater generating
source.
Cristino
et al
. (2012) underline that it is very difficult to keep the water at
the ideal temperature in order to control the multiplication of
Legionella
in the
entirewater distribution systemand therefore there is noguarantee that the entire
system will not have this microorganism. The authors also emphasize that it is
practically impossible to eliminate
Legionella
from a water distribution system
that is already contaminated by this microorganism.
Though the heating of the water at temperature above 60 °C is the process
to control
Legionella
that is indicated by many researchers as being the most
efficient one and so the most widely used, other processes can be employed for
this purpose, such as: ultraviolet radiance; the use of chemical biocides such as
chlorine, chlorine dioxide, chloramines, ozone or iodine; or yet by ionization of
copper and silver (Triassi
et al
., 2006, Hosein
et al
., 2005, O’Neill andHumphreys,
