237
aerobic microorganisms is below 105 UFC∙L-1. They also recommend that
during the steps II to VIII, and mainly during the step VII, workers must
use a mask to prevent the inhalation of aerosols contaminated by
Legionella
.
From the review made here, there is no consensus on which is the most
indicated disinfection process to control
Legionella
in water distribution
systems,whichmay indicate that the characteristicsof the systemdo interfere
in the efficiency of the disinfection process. A process that is efficient to
one system may be inefficient to another. Therefore, it is important to
evaluate regularly the efficiency of the process chosen and to replace it as
soon as possible when observing that it is ineffective to control
Legionella
.
The examples presented below show how difficult it can be to choose
the water disinfection process in view of the results obtained in several
field researches. Dareid
et al
. (2002) and Shuval
et al
. (2009) mentioning
multiple authors, states that even though the circulation of hot water at
a temperature above 55 °C seems to be efficient to control
Legionella
and
hence to reduce the risk of outbreaks, it is a hard-working technique and
must be repeated several times during the year. Blanc
et al
. (2005) concluded
that the best procedure to disinfect the water distribution systems is the use
of hot water at a temperature higher than 50 °C. According to the authors,
this procedure was proven to be more efficient than both the ozonation
of water and the use of copper and silver ions. Chenb
et al
. (2008) on the
other hand, confirmed that copper and silver ionization was efficient to
eradicate
Legionella
from both cold water and hot water piping indicating
this disinfection process as an attractive alternative. However, the literature
shows outbreaks caused by
Legionella
even when using this technology,
besides of some reports informing the occurrence of
Legionella
spp. tolerant
of silver ions. Hyperchlorination, according to Chenb
et al
. (2008), can
