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interrupt the transmission of
Legionella
in some cases for up to two years,
but the complete eradication using free chlorine and chlorine dioxide is not
commonand still presents a series of disadvantages suchas corrosion, elevated
costs and generation of undesirable by-products. Therefore, the conclusion
fromthe exposed is that there is no consensus concerning the best disinfection
process forwater distribution systems. Lin
et al
. (1998) recommend, whenever
possible, the use of more than one disinfection process, taking into account
that if an operational failure occurs in one of them, the other can still be used
as replacement.
Another aspect that should be considered is the presence of biofilms in
thewater distribution systemand the associationof
Legionella
withprotozoan.
O’Neill andHumphreys (2005) concludedfromseveral reportsof the literature
that once the
Legionella
cells are established in a water distribution system,
the eradication is very difficult to be achieved. This difficulty, according to
these authors, is due to the development in biofilms and to the association
of
Legionella
with certain protozoan, because these two conditions hinder
the disinfection process. Being so, one of the possible measures to avoid the
presence of
Legionella
would be to avoid the formation of biofilms since the
starting of the operations in a water distribution system and to ensure, since
the beginning, the correct dosage of an agent with biocidal properties. Kwaik
et al
. (1998) and Marchesi
et al
. (2011) affirm that there are many strategies
that can be used to try to eradicate or control the presence of
Legionella
in
reservoirs and inwater distribution systems, but they emphasize that it should
begin with the prevention of water contamination by protozoan which would
protect the
legionella
cells from the disinfection processes commonly used.
The Association ofWater Technology (AWT, 2003) insists in highlighting
some points related to the control of
Legionella
: the biocidal agents available
