233
According to Liu
et al
. (1994), the advantages of the use of copper and
silver ions to eradicate
Legionella pneumophila
in water distribution systems
include the relatively low cost, the easy maintenance, the absence of toxic
by-products, the presence of residual disinfectant action and stability at high
temperatures, differently from chlorine and ozone which degrade under
high temperatures. Another advantage indicated by the authors is that the
use of copper and silver ions retards the recolonization of the surfaces for 6
to 12 weeks. As disadvantages that can mention are: the excessive presence of
silver ions that can cause the darkening of the water and porcelains used in
sinks and toilets; and the concentration of ions present in the water that can
oscillate over time and must have the concentrations regularly monitored by
atomic absorption. According to Lin
et al
. (2011), copper concentrations must
be monitored weekly, and silver concentrations must be controlled twice a
month. For these authors, also, it is worth mentioning the fact that ionization
has a longer efficiency, adding a greater margin of safety, contrasting with
new installations, lower concentrations are efficient to eradicate
Legionella
spp, with copper concentration between 0.2 and 0.4 mg∙L
-1
, and between 0.02
and 0.04 mg∙L
-1
for silver.
Table 1
– Distribution of positive samples for
Legionella
in terms of the copper
concentration in the water (Leoni
et al
., 2005).
Microorganism
<10
Copper (µg·L
-1
)
10-25
25-40
>40
Legionella
pneumophila
64.2
56.4
38.1
29.2
Legionella
spp.
20.3
7.7
28.6
25.0
Positive Samples (%)
