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HEALTH AND SANITATION
Legionella – copper-silver ionization
(CSI) operational conditions
Maintaining copper and silver at the levels recommended by the
manufacturer is a best practice in achieving operation effectiveness.
By Environmental Protection Agency, document EPA 810-R-16-001
PARAMETER CONDITIONS INDICATING
OPERATIONAL EFFECTIVENESS
Note that monitoring typically includes measurement of
the total metal concentration, which includes copper and
silver that are bound up as complexes, as well as copper
and silver ions. The presence of copper and silver ions
is thought to be critical for treatment effectiveness,
so maintaining proper pH and avoiding interfering
materials (e.g. phosphates, chlorides) is also important
(Zevenhuizen et al., 1979).
CSI systems can
be plumbed into
either the cold
water entry
pipe or plumbed
into the hot
water line.
Examples of interferences include:
• In the presence of 20–40 mg/L of chloride ions,
silver ion levels are significantly (60 per cent)
decreased by complexing with chloride (and are
presumably less microbiocidal) (Lin et al., 2002).
• Phosphates, such as those added for corrosion
control, can bind to copper ions as well as silver
ions, reducing their treatment effectiveness
(Zevenhuizen et al., 1979).
The presence of dissolved organic carbon at 2mg/L,
calcium at 100mg/L, magnesium at 80mg/L, and
bicarbonate at 150mg/L did not appear to decrease the
treatment efficacy of copper and silver ions against
L. pneumophila in a laboratory study (Lin et al., 2002).
The impact of pH on the ionic nature (and thus the
microbiocidal action) of copper in solution is also
January 2018 Volume 23 I Number 11
important. At pH levels >6.0, copper forms insoluble
complexes with a number of compounds. While in the
pH range typical of potable waters (pH 6–9), silver ions
are not diminished. In a controlled laboratory study,
Lin et al. (2002) found that at a pH of 7, exposure to
0.4mg/L of copper resulted in a 4-log (99.99-percent)
reduction of L. pneumophila in one hour; however,
at a pH of 9, there was no appreciable decrease in
L. pneumophila over the same period of time with
the same copper exposure. Dziewulski et al. (2015)
demonstrated efficacy of CSI under alkaline water
conditions (pH 8.0-9.8) and found that silver ions
controlled the L. pneumophila serotypes 1 and 6, and
L. anisa.
With regard to the effects of temperature, one study
(Landeen et al., 1989) found no significant difference
in L. pneumophila inactivation rates in experiments
conducted at room temperature (21–23 degrees C, or
69.8–73.4 degrees F) and elevated temperature (39–40
degrees C, or 102.2–104 degrees F) using water with
0.2mg/L free chlorine, with or without 400µg/L of
copper and 40µg/L of silver.
INSTALLATION CONSIDERATIONS
CSI systems can be plumbed into either the cold water
entry pipe or plumbed into the hot water line. Care
should be taken to install devices downstream of any
process that will remove or exchange copper and silver
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