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Zeonda™ - Circulation Method
Scientific background
Conventional disinfection methods
Technical criteria for a legionella-safe
system
Basic principles
Features
Special mixer type enables all water to circulate
Other products
Usability
Tested by the Swedish Institute for Infectious
Disease Control
High safety
Installation
Zeonda™ - Circulation Method - practical
application
Practical
application
Scientific
background
After having studied the reports from a
large number of decontamination projects, a group of researchers
at the University of Pittsburgh and the Veterans Administration
Medical Center in Pittsburgh, Pa, USA concluded that there
is only one scientifically proven method of keeping hot water
clear of legionella, namely by continually keeping the water
at a temperature of at least 60°C throughout the water
system.
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Experiments
have shown that free legionella bacteria in water die
in a couple of hours at 50°C, in a couple of minutes
at 60°C and within seconds at 70°C.
When protected by the biofilm, sludge and sediment
found in pipe systems, mixers and showers the bacteria
can survive for 15 minutes or more at 70°C.
The same applies to the bacteria that colonise the
free amoebas always found in this water.
Legionella also survives freezing. |
Conventional disinfection methods
Conventional methods of disinfecting
water systems do not give full and lasting protection.
Flushing with high-pressure hot water and
chlorination are only acute measures and do not give long-term
protection as new legionella bacteria are introduced into
the building’s water system via the municipal water
system. A continuous inflow of legionella bacteria requires
continuous disinfection.
The continuous methods that have been available
until now do not solve the problem.
- They are unable to disinfect the whole
system with lasting effect
- They require trained personnel and careful
monitoring
- Both installation and operating costs
are high
- Environmental risks and secondary health
hazards also exist
Technical criteria
for a legionella-safe system
The technical criteria for a legionella-safe
system are therefore:
- Continuous circulation of both hot and
cold water through the entire water system - nowhere may
water remain stationary or be heated up
- No “pockets” of stationary
water
- Cold water must always be kept below
20°C and hot water above 60°C, killing legionella
bacteria in hot water and preventing growth in cold water
Basic principles
The basic principle of the Zeonda Method
is to permanently keep all parts of the hot water system at
about 60°C and the cold water at under 20°C by ensuring
that the water is circulating continuously all the way out
to the mixer at every tap point. Nowhere must the water remain
stationary and be cooled or heated up. In this way bacteria
in hot water are killed and legionella growth in cold water
is prevented. Moreover, the circulation water is kept at a
temperature of at least 57°C, thus ensuring that there
can be no legionella growth. The heart of the Zeonda™
Circulation Principle is the patented Zeonda™ mixers
and circulation units.
The basic principle is to permanently
keep hot water at least 60°C from the central heating
station and the cold water under 20°C in all parts of
the pipes by ensuring that water is circulating continuously
all the way out to the mixer at every tap point. Circulation
water is kept at 57°C at least. The growth points have
now been dealt with, circulation pipes are in place and the
mixers have been replaced with Zeonda™ mixers.
Features
- Continuous thermal decontamination of
the whole hot water system
- Stop to bacteria growth in the cold water
system
- No increase in operating or maintenance
costs
- Better economy in the operating phase,
lower water consumption, lower heating costs
- No need for specially trained personnel
- Improved comfort because hot or cold
water is delivered immediately when water is drawn
- No running off of lukewarm water, leading
to savings of both water and energy
- When the water system is newly installed
or has been unused for some time (due to repairs, in homes
empty during holidays or hospital wards, etc.) the system
can be decontaminated without extra work effort by letting
water at 80°C circulate through both the cold water
and hot water sides of the system. In such cases users must
be notified in advance.
- Option of using energy-saving shower
heads with small drop size
- The most environment-friendly way
of preventing bacteria growth. Only water and heat are used
and there is no use of chemical additives that involve risks
of harm to people, pipe systems and the environment.
The picture on the left shows a traditional
bathroom. The middle and right pictures the Zeonda™
Circulation Method being used. The middle picture shows a
3-pipe system and the picture on the right shows a 4-pipe
system.
Special mixer
type enables all water to circulate
The heart of the Zeonda™ Circulation
Method is mixers that enable all water to circulate. Because
the mixers are fitted with a circulation attachment, water
circulates right out to and through the mixers. The mixers
are designed so that mixing chambers, shower hoses and shower
heads are drained after every use. This means that no colonies
of legionella bacteria will be able to develop there.
Outline diagram of the Gustavsberg Zeonda™
mixer Gemedic, a shower mixer with recirculation on both cold
and hot water sides and automatic draining.
Other products
Usability
The Zeonda™ - Circulation Method can
be used in all types of water supply systems. In new construction
the method is easy to apply. Major renovation work, such as
pipe replacement, etc., is a good opportunity to apply the
method. However, systems that are particularly sensitive in
terms of legionella such as water systems in hospitals, nursing
homes, elderly and seniors housing and hotels should be renovated
specially in order to install the Zeonda™ Circulation
Method.
Tested by
the Swedish Institute for Infectious Disease Control
The Swedish Institute for Infectious Disease
Control has been commissioned by Zeonda AB to carry out a
test of the performance of the Zeonda system in a test facility.
The test corresponded to a hot water system in a three-storey
multi-dwelling building with four apartments. The test facility
has a primary and a secondary hot water cycle and joint circulation
of hot and cold water in a third circulation pipe at a temperature
of at least about 54°C. This is made possible by using
the Zeonda™ - Circulation Method with the special Zeonda
mixers and Zeonda showers.
Legionella bacteria were added at very high
concentrations on the hot water side to determine reduction
and possible bacteria growth in the test facility. The temperature
was reduced to 37°C while 15 billion legionella bacteria
were added, and the bacteria were allowed to circulate for
an hour. Then the temperature of the flow water was increased
to 66°C with a hot water recirculation temperature for
the Zeonda system of 53-54°C. The results show that there
was no incidence of legionella bacteria at all on the hot
water side after circulation for only one hour and that the
bacteria never reappeared in the pipe system. So the Zeonda™
Circulation Method achieves good safety.
High safety
The results of the tests carried out by
Swedish Institute for Infectious Disease Control in the test
facility show that the around 15 billion legionella bacteria
were killed off in less than an hour and that they never subsequently
returned to the pipe system. To simplify checks on the water
system the plant can be fitted with Zeonda™ biofilm
chambers. The biofilm chambers are connected to the system
using fast couplings so that they can be removed easily without
special tools and be sent to a laboratory for analysis.
When a facility is newly installed or if
it has not been used for a long period, for instance during
holidays or renovations, the Zeonda™ - Circulation Method
enables total decontamination with the circulation of water
at a temperature of 80°C through the whole system. The
procedure is controlled from a sub-station and requires no
extra work out in the system.
Installation
Download installation PDF
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