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Heavy metals
, such as copper and silver ions, have bactericidal activity.
So, according to the AWT (2003), water flowing at the interior of a chamber
containing copper and silver electrodes is a process that can be used in the
water disinfection due to the presence of copper and silver ions in the aqueous
stream. Copper ions (Cu
2+
) and silver ions (Ag
+
) positively charged, obtained
in their respective electrodes, interact with some negatively charged sites of
the microorganism wall causing a modification in the permeability of this
structure. This action, together with the protein denaturation, causes the lysis
of the cell and consequently its death (Liu
et al
., 1994, Lin
et al
., 1998, Kim
et al
., 2002, AWT, 2003). According to Stout and Yu, the use of copper-silver
ionization was introduced as an option to the control of
Legionella
to overcome
the disadvantages of rinsing with hot water and hyperchlorination.
Kim
et al
. (2002) mention that the necessary dosages to promote the
disinfection of the water with metal ions range from a few hundreds of µg∙L
-1
of copper, and from a few tens of µg∙L-1 of silver. Liu
et al
. (1994) verified that
with the use of copper and silver concentrations higher than a 0.4 mg∙L
-1
and
0.04 mg∙L-
1
, respectively, it was possible to eradicate
Legionella
from the water
distribution system in three months. Lin
et al
. (1996) obtained a destruction
of 6 log cycles (99.9999%) of
Legionella pneumophila
in 2.5 hours using
copper ions at the concentration of 0.1 mg∙L
-1
. Using only silver ions at the
concentration of 0.08 mg∙L
-1
, 24 hours were required to obtain the same level
of destruction. These authors verified that the copper and silver combination,
with both ions at the concentration of 0.04 mg∙L
-1
, presents synergy effect
and requires time inferior to 2 hours to cause a reduction in the population
of
Legionella
of approximately 5 log cycles. Kim
et al
. (2002) mention other
studies in which there are evidences that the use of copper ions (0.17 mg∙L
-1
)
