Health and sanitation
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Mòdol et al. (2007) described how a large
hospital experienced success in decreasing
the number of positive legionella samples
after initiating CSI. The hospital had
discontinued the use of chlorine in the
hot water system due to difficulties in
maintaining minimum concentrations at
distal points in the building’s premise
plumbing system. It also discontinued
frequent superheating due to pipe damage
and poor compliance with heating and
flushing procedures. Initially, the copper
and silver levels were maintained at 0.1–
0.3mg/L and 0.01–0.03mg/L, respectively.
While the treatment system was under
repair for two months, the percentage of
positive samples for legionella increased
from 20% to 65%. Following the
interruption in treatment, hospital staff
increased copper and silver concentrations
to 0.4 and 0.04mg/L. Legionella samples
taken after the increase were 16% positive.
Blanc et al. (2005) reported that no
significant difference was observed in the
percentage of water and biofilm samples
positive for legionella spp. after CSI
treatment was installed in 1999. The CSI
system electrodes were composed of 8%
silver and 92% copper, and the copper
concentration in the water was 0.3mg/L. A
significant reduction in legionella isolates
was observed after the hot water system
temperature was increased from 50 to 65
degrees C (122 to 149 degrees F) in the
year 2000.
Survey results by Stout and Yu (2003)
showed that of 13 hospitals reporting at
least 30% legionella-positive samples
before CSI treatment began, nine hospitals
reported a sustainable (over a period of
6–9 years) decrease in the number of
legionella-positive samples; five hospitals
reported no positive samples after
treatment. This survey also showed that all
www.plumbingafrica.co.za
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of the hospitals reported cases of hospital-
associated legionnaires’ disease before
CSI treatment, and all but one reported no
cases after treatment.
Lin et al. (2002) studied the effects of pH
and other water quality parameters on
CSI treatment for legionella control using
water from a hospital hot water system. At
pHs of 7.0 and 9.0, copper ions achieved
a 6-log and 1-log (99.9999 and 90%)
reduction, respectively, in the number of
L. pneumophila in 24 hours. Silver ions
achieved a 6-log reduction in 24 hours
at all ranges of water quality parameters
tested.
Based on four years of monitoring data,
Kusnetsov et al. (2001) reported that
legionellae were no longer detected in the
circulating warm water of a hospital water
system after CSI treatment was employed
and silver concentrations were increased
to levels greater than 3µg/L. However,
water samples collected from taps and
showers that were not used on a regular
basis showed that even a high silver
concentration (55µg/L) did not prevent
growth of legionella.
Rohr et al. (1999) indicated that CSI had
an initial impact on legionella occurrence
in the hot water system of a German
university hospital, where 100% of
sampling sites were positive for legionella
before treatment and 55% of sampling
sites had positive results one year after
treatment was initiated. Over the next
three years, 75–78% of samples were
positive for legionella. However, Lin (2000)
disagreed with Rohr et al.’s (1999) results
that the CSI system did not effectively
control legionella in this system. Lin (2000)
pointed out that the CSI system was not
effective because it did not maintain an
adequate concentration of copper and
silver ions in the treated premise plumbing
system (200–400µg /L of copper and 20–
40µg /L of silver was crucial). Lin (2000)
also noted that Rohr et al. did not provide
evidence for the development of legionella
resistance to copper or silver. Rohr (2000)
responded to Lin’s (2000) comments, and
explained that the purpose of the study
was to evaluate control of legionella using
a CSI system that met German regulations
limiting silver ion concentrations to a
maximum of 10µg/L.
States et al. (1998) reported that CSI
treatment was successful in reducing the
percentage of samples testing positive for
legionella from 100% to less than 17% on
average over a two-year period.
Lin et al. (1996) found that L. pneumophila
serogroup 1 was completely inactivated
(6-log (99.9999%) reduction) within 2.5
hours using copper ions at concentrations
of 0.1mg/L without silver ions, and more
than 24 hours was needed to achieve
a similar reduction using silver ions at
concentrations up to 0.08mg/L without
copper ions. When both copper and silver
ions were used, inactivation was achieved
at copper and silver concentrations of
0.04mg/L.
Based on laboratory studies with filtered
well water (pH 7.3), Landeen et al. (1989)
determined that copper ions (at 0.4mg/L)
and silver ions (at 0.04mg/L) can achieve a
3-log (99.9%) reduction in L. pneumophila
at room temperature when the contact time
is at least 24 hours. PA
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The National Environmental Methods
Index (https://www.nemi.gov/home/) “is a
searchable database that allows scientists
and managers to find and compare
analytical and field methods for all phases
of environmental monitoring.”
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May 2017 Volume 23 I Number 3