Download 10 YEARS` INNOVATION AND QUALITY THE BASICS OF Ozone O3

10 YEARS’ INNOVATION AND QUALITY
THE BASICS OF Ozone
INTRODUCTION
Ozone is a gas formed when oxygen is exposed to either a high ultraviolet light
intensity (as occurs in the atmosphere upper layers) or a high power field (known as
corona discharge) able to separate both of the atoms of which it is composed and lead
to a new oxygen triatomic molecule. Ozone is a powerful oxidizing agent, disinfectant
and deodorizer.
It has a very peculiar odor, after which it was named (from the Greek word ozein =
smell). This odor is particularly evident in lightning storms or specific lightning
discharges.
The high instability of the ozone molecule makes it necessary to generate it in situ.
Its high reactivity is exceeded only by fluorine. However, within the commonly used
chemical compounds, ozone takes the lead as regards oxidation potential. As a result,
this compound is one of the most powerful oxidizing agents ever known.
Compound
O3
HOCl
Cl2
NH2Cl
Power (mV)
-2.07
-1.49
-1.36
-0.75
Ozone most interesting properties are its solubility in water and its stability in both liquid
and gaseous media, since these enable ozone to be applied as a disinfectant.
OZONE GENERATION
There are several technologies that lead to ozone generation, among which the two
technologies mostly applied are: UV radiation and Corona Discharge. The latter, which
has been adopted by FG ingeniería, is the one that achieves greater ozone
concentration in either air or oxygen and therefore, the most convenient one in
industrial generators.
In the generation process, gas containing oxygen (for example, dry air) is circulated
through a space where a strong electric field will be applied. Such energy leads to
oxygen dissociation, which recombines with new molecules in order to generate ozone.
Generation
Cooling water and ground electrode
(stainless) steel
O2 / Air
O3
High voltage electrode
Dielectric
(glass)
10 YEARS’ INNOVATION AND QUALITY
OZONE SOLUBILITY
When referring to ozone solubility in water, it is very important to distinguish between
saturation solubility and the solubility that can be operationally accomplished in a water
treatment system. In short, the important thing will be to achieve enough concentration
for the intended treatment. This value will generally be well below saturation.
Ozone final concentration in water depends on the concentration in the gas phase, gas
pressure, water temperature and the gas/liquid exchange technology. The first one
depends on the technology used in the generation and the carrier gas (air or oxygen).
FG ingeniería designs the contact towers in order to optimize the exchange, producing
an equipment unit of limited dimensions.
Contact towers developed by FG ingeniería are made of 304L / 316L stainless steel
and have sanitary features.
Usual concentrations in water treatment systems range from 0.3 to 1.5 ppm.
The value of C x t is the parameter for controlling micro-organisms, endotoxins and
pyrogens. It has been experimentally proved that a value of C x t = 3 kills a wide range
of bacteria with a concentration of 5 x 10³ CFU/ml total bacterial count. Even so, values
of C x t = 6 ensure complete destruction of bacterial flora, pyrogens and endotoxins.
Mechanisms of action on different types of micro-organisms.
Effects on bacteria: Ozone seems to attack the membrane first (Giese and
Christensen 1954, Christensen and Giese 1954), or through the glycoproteins or
glycolipids (Scott and Lester 1963), or through certain amino acids such as tryptophan
(Golstein and McDonagh1975).
Ozone also interrupts the bacterial enzymatic activity, acting on the sulfhydryl groups in
certain enzymes. Bacterial death may result directly from the changes in cellular
permeability (Murria et. al. 1965), and it is likely to be followed by cellular breakage.
Since oxidation and inactivation reactions always occur rapidly, Bringmann (1954)
considered that ozone acted differently from chlorine. He thought that chlorine acted in
a selective manner by oxidizing certain enzymatic systems while ozone acted as a
“general oxidizing agent”.
Ozone acts on nuclear material; Christensen and Giese (1954) and Scott and Lesher,
(1963) showed that ozone affects purines and pyrimidines in nucleic acids.
Effects on Viruses: The first place where ozone acts is undoubtedly the viral
envelope, especially the proteins that form it. Ozone seems to change those places in
the viral envelope that are used by the virus to bind to cell surfaces.
DISSOLVED OZONE STABILITY
Once inside the liquid, ozone must remain there for a certain period in order to achieve
its oxidizing effect. Dissolved ozone mean life is usually longer than such a
requirement.
The decomposition of ozone in water (given the absence of pollutants) is accomplished
by ozone self-recombination, after which it becomes oxygen once again. Such
decomposition will be dependent on:
10 YEARS’ INNOVATION AND QUALITY
Temperature
Effect of UV rays
pH of the media
In neutral water and at temperatures close to 18ºC, ozone will have a 20-minute mean
life.
In the case of disinfection of hemodialysis distribution circuits, this allows cleaning up
the system at the end of the working day so that it will be found sterile and free from
ozone the following day. After a short rinse time, the system will be appropriate for its
operation; even if there are any deficiencies in the rinsing procedures, ozone is selfdegradable within a short period, only oxygen being left as waste.
FG ingeniería’s equipment ensures ozone degradation at the time of distribution to
hemodialysis rooms through water treatment with UV radiation, which accelerates
ozone degradation and removes every trace of it.
DISINFECTANT PROPERTIES
Ozone is highly effective at very low concentrations. In vegetative forms, E. Coli is one
of the most sensitive bacteria while Gram-positive cocci, Gram-positive bacillus and
mycobacteria are more resistant. Anyway, there is no great difference in the sensitivity
of all of them, since they are all very sensitive to inactivation through ozone.
For example, in trials carried out with E. Coli, 99.99% reductions (4 logs) were
measured in 1 minute and with 9 micrograms/ liter.
Very similar results were achieved with Staphylococcus sp. and fluorescent
Pseudomonas. In the case of Enterococcus faecalis (formerly known as Streptococcus
faecalis), 2 minutes were needed for the same effect, while in the case of
Mycobacterium tuberculosis 6 minutes were needed.
The disinfectant effect can be quantified according to C x t (concentration in ppm times
ozone-water contact time in minutes) values. Although such values are affected by
temperature and pH, among other factors, we are able to state globally that a value of
C x t = 2 ppm.min for ozone produces the same effect that a value of 500 ppm.min for
chlorine, 100 000 for peracetic acid in the removal of highly-resistant organisms.
Specifically in the case of endotoxins, ozone has shown excellent reductions (> 99%)
with values of C x t = 6. This represents a definite advantage since other disinfectants
do not even have the ability to remove endotoxins.
BENEFITS OF OZONE
In the traditional system of hemodialysis water treatment, ozone starts to take up a
leading position within its layout since it has several advantages, which are not only
chemical but also operational:
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Its disinfection rate is a thousand times higher than that of chlorine.
It effectively removes bacteria, mycobacteria, viruses and endotoxins.
It removes fungi, algae and spores.
It oxidizes organic and biological compounds without leaving unwanted byproducts.
It is very easy to rinse from cleaned up systems.
10 YEARS’ INNOVATION AND QUALITY
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It prevents risky handling of other chemical products.
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It does not require dilution calculations or maneuvers.
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It is absolutely convenient in relation to its operating cost (only the electric
power involved).
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It is self-degradable within short periods, leaving oxygen as waste.
OZONE APPLICATIONS
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Hemodialysis water treatment.
Disinfection of tanks and pipes.
Water for human consumption.
Water in cooling towers and swimming pools.
Ultra-pure water for pharmaceutical processes.
Effluent treatment.
Our equipment units intended to be applied to hemodialysis have brought together all
those advantages and qualities of ozone, taking into consideration the operational
requirements and requests of an hemodialysis center.
Much remains to be said about this noble product. Therefore, our company places at
your hemodialysis center’s disposal all the additional technical information available to
answer any specific inquiries or doubts that may eventually arise.
Eng. Hernán Yannuzzi
fg ingeniería
Bibliography:
Ozone in Water Treatment – Cooperative research Report 1991