235
distribution system for up to one year. However, according to these authors, to
use of UV lamps alone does not ensure the control of
Legionella
in coolingwaters
due to the absence of residual action and to the existing turbidity in the water.
Several studiesprove that ultraviolet lightmust beused togetherwithanother
disinfection process (hyperchlorination or hot water rinsing) in order to ensure
the control of the population of
Legionella
in water distribution systems. This
process causes only local disinfection and does not ensure the disinfection of the
water all along the entire distribution network, as colonies of
Legionella
can be
located in biofilms along the pipes and in places where water is stagnated (Kim
et al
., 2002; Lin
et al
., 1998; Liu
et al
., 1995; Lin
et al
., 1998; Franzin
et al
., 2002).
Lin
et al
. (2011) and Liu
et al
. (1995) state that the use of ultraviolet radiation,
together with pre-filtration, can prevent the presence of
Legionella
in the water
of hospitals for months, provided that a hot water rinsing was previously applied
and that the lamps are installed close to the point of use of thewater. Other studies
also recommend also that the lamps are installed close to the points of use of the
water, as showers and faucets (Franzin
et al
., 2002; Kim
et al
., 2002).
According to Liu
et al
. (1995), the advantages of using ultraviolet radiation
include the easy installation, low cost of operation and no adverse effects to
the water or the pipes. However, these authors mention that the filters must be
installedbefore the lamps are reachedby thewater inorder toavoid the formation
of incrustationsonthemto thenensure their efficiency inthedisinfectionprocess.
The recommendation of the installation of filters was evidencedwhen it was seen
that after one month since the disinfection in the water distribution system there
were colonies of
Legionella
in thosedistribution systemswithout filters, but it took
five months for them to appear in the systems with water filtration system. This
disinfection process of the water is also inefficient in water distribution systems
where there are biofilms (AWT, 2003).
