ASHRAE Journal - April 2020 - 64

COLUMN HVAC APPLICATIONS

FIGURE 1 Widespread municipal water risks in the

United States.
A

B

A Source water contaminated with pathogens.
B Legionella in municipal drinking water
storage tanks.

Giardia

The EPA's Safe Drinking Water Act requires a 3-log reduction
in Giardia and a 4-log reduction in viruses from the source
water to the finished water leaving the treatment plant.

Legionella

"The EPA believes that if Giardia and viruses are
controlled, Legionella will also be controlled."8

C 29% of cold-water taps
contain Legionella pneumophila.2
D Potable cooling tower makeup water is
frequently contaminated with Legionella
pneumophila from public water supplies.

Most source waters are contaminated
with both Legionella and Giardia.6,7

Statistical analyses were done to establish correlations
between Legionella, Acanthamoeba and temperature as
well as other independent variables like total organic
carbon (TOC), total organic matter (TOM), particle size
and pH. These variables were recorded at the time of
sampling for use in the analysis.
The results of the study indicated that Legionella bacteria were present in 66.7% of the samples; Legionella
pneumophila was present in 33% of samples; and Legionella
pneumophila serogroup 1 was present in 28% of the
samples. In contrast, Escherichia coli (commonly known
as E. coli) and Giardia were undetected. This shows that
while efforts to control E. coli and Giardia work, the efforts
to control Legionella do not. Another important finding:
there was a significant correlation between Legionella
and Acanthamoeba. Legionella bacteria will amplify and
increase its virulence inside amoeba. This further supports a relationship between the two, so the detection
of Acanthamoeba may be used as a potential indicator of
Legionella contamination.
The results of this nationwide study, the first of its
kind, demonstrate that Legionella that is present in the
municipal water system will continue to survive in
drinking water storage tanks in addition to surviving
in large buildings' plumbing systems. This reinforces
the need for anti-Legionella measures at the water treatment plant and distribution system-before the water
gets to water storage tanks where it will then be passed
64

ASHRAE JOURNAL

ashrae.org

APRI L 2020

on to buildings and homes.

Cold Tap Water Study2
The next key study on Legionella levels is the cold water
tap study undertaken by the EPA aimed at determining whether Legionella was present in cold water used by
the general population. This is important because, out
of the 6,868 cases of Legionnaires' disease reported in
2009- 2010, only 2.6% were outbreak events, while the
remaining 97.4% were sporadic.4,5
As with the storage tank study, samples were taken
from diverse regions across the United States. Between
January 2009 and December 2010, the EPA took a total
of 269 samples from 68 residential and commercial
locations in 25 states, one territory and one federal
district.
Researchers sampled cold water from 29 kitchen sinks,
21 bathroom sinks, 17 drinking water fountains and one
refrigerator water dispenser. Of the 68 taps sampled, 66
were from municipal supplies. Samples were taken after
taps were allowed to run for 15 seconds to ensure that
the supply was from the potable water supply and no hot
water was included. No site had secondary water treatment (although the refrigerator had a filter).
A qPCR analysis was carried out and tests were performed to determine levels of Legionella pneumophila and
Legionella pneumophila serogroup 1 (again, the most disease-causing variant). Twenty-nine percent of samples


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ASHRAE Journal - April 2020

Table of Contents for the Digital Edition of ASHRAE Journal - April 2020

Contents
ASHRAE Journal - April 2020 - Intro
ASHRAE Journal - April 2020 - Cover1
ASHRAE Journal - April 2020 - Cover2
ASHRAE Journal - April 2020 - 1
ASHRAE Journal - April 2020 - Contents
ASHRAE Journal - April 2020 - 3
ASHRAE Journal - April 2020 - 4
ASHRAE Journal - April 2020 - 5
ASHRAE Journal - April 2020 - 6
ASHRAE Journal - April 2020 - 7
ASHRAE Journal - April 2020 - 8
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ASHRAE Journal - April 2020 - Cover3
ASHRAE Journal - April 2020 - Cover4
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