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Until now, several measures have been mentioned to try to control
the presence of
Legionella
spp. in water distribution systems. However, the
contaminationby
Legionella
canalsooccur in cooling towers, andpeople can
be contaminated by inhaling the aerosols generated during their operation
(Mouchtouri
et al
. 2010). A possible methodology that can be applied to
reduce the population of
Legionella
in this type of equipment consists of the
following steps (AWT, 2003): I) to turn off the fans of the cooling tower;
II) to maintain the intake valves of replacement water (make up) open and
the circulating pumps in operation; III) to close all the external air intakes
located within a range of 30m from the cooling tower; IV) to add a chlorine-
based disinfectant until reaching a free residual chlorine concentration of
50mg∙L
-1
; V) to add a dispersant agent to the water after 15minutes from the
addition of the disinfectant and then to keep the concentration of residual
free chlorine equal to 10 mg∙L
-1
per 24 hours; VI) to drain the system, re-fill
it and then repeat the steps IV and V for at least one more time in order to
remove all the algae films attached to the surfaces of the equipment; VII)
by using a brush and a hose, to scrub thoroughly all the components in
contact with water, including the sprinklers; VIII) to circulate the water
with free residual chlorine concentration of 10 mg∙L
-1
per one hour and
then rinse the system until noting the absence of sediments; IX) replenish
the system with clean water and restart the operation. Mouchtouri
et al
.
(2010) observe that this process can be executed either in one hour, in case
the Step V described above uses a concentration of free chlorine equal to
50 mg∙L
-1
, or in two hours, by using a concentration of free chlorine equal
to 25 mg∙L
-1
. Also, according to Mouchtouri
et al
. (2010) the disinfection
process of the cooling tower can be considered successful if after 2 to 7 days
the
Legionella
spp. population is below 103 UFC∙L
-1
and the counting of
