Ozonator for sterilizing, decontaminating, disinfecting,...

Details Ozonator for sterilizing, decontaminating, disinfecting,... Ozonator for sterilizing, decontaminating, disinfecting,...

2001-08-24

2004-03-30

Mayekar, Kishor (Department: 1753)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

With means applying electromagnetic wave energy or...

C422S186070, C422S186150

Reexamination Certificate

active

06713027

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains generally to apparatus for sterilization of objects such as dental instruments and more particularly to such sterilization using ozone generation.
2. Background Art
Unlike sanitizing or disinfection, where certain contaminants can be selectively destroyed, sterilization requires that the viability of not some, but rather all, living contaminants is destroyed. The use of ozone treatment and ozonators to disinfect and sanitize is not per se unique. Both have a long history of use for these purposes. Ozone is used to purify drinking water, disinfect bottled water, treat industrial waste, deodorize air and sewage gases, and to further extend the life of perishables preserved by cold storage (ozone remains a strong disinfectant even at temperatures below −150° F.). However, hitherto, the complete sterilization of surgical instruments has not been achieved through ozone treatment.
Ozone, O
3
, or triatomic oxygen is a naturally occurring molecule. It is produced in the low pressure stratas of earth's atmosphere as the result of the action of ultra violet radiation upon the O
2
molecule and, otherwise, as the result of electrical discharges which naturally occur in the earth's atmosphere. O
2,
the more stable molecular form of oxygen, is split into atomic oxygen when bombarded with either electrons or electromagnetic radiation, like UV light, having energy sufficient to split the O to O double bond of O
2
(6 eV to 7 eV). The highly reactive single atomic oxygens then bond with other O
2
molecules to form O
3
(3O
2
(g)+Energy=2O
3
(g)). Near the Earth's surface the concentration of this trivalent oxygen molecule in rural atmosphere is usually about 0.002-0.003 PPM (parts per million).
The German chemist Christian Friedrich Schonbein first discovered O
3
in 1839. He named the molecule ozone, from the Greek ozein “to smell”, as ozone has a readily identifiable acrid odor which can be recognized by olfaction at fewer than 0.015 PPM in atmosphere and becomes rather unpleasant above 0.1 PPM in atmosphere. It appears as a bluish hue at 5 PPM in atmosphere.
With the validation of the germ theory of disease, after Pasteur's ground breaking U tube experiments reported in the
Annales des Sciences Naturelles,
4th series, Vol. 16 (1861), the germicidal action of ozone was quickly recognized. O
3
is a highly unstable molecule, which readily reacts with other matter to form O
2
by losing one of its constituent atomic oxygens to the reaction. Both O
3
and O are highly reactive. Both have oxidizing potentials which are greater than that of hypochlorous acid, a bleaching and chlorinating agent and disinfectant, which itself is recognized as a very strong oxidizing agent. The germicidal power of Cl (chlorine) is dependent upon the release of free hypochlorous acid. Yet, the oxidizing potential of HClO is only 1.36 V. The oxiding potential of O is 2.07 V. The oxidizing potential O
3
is 1.67 V. O
3
is second only to F (fluorine) and O in electronegative oxidation potential, with F being the most electronegative of the elements on the Pauling Scale.
O
3
is highly reactive with hydrocarbons and other unsaturated molecules. On contact, this strong oxidant reacts with the hydrophobic fatty acid tails of the phospholipids which form the phospholipid bilayer of bacterial cell membranes. This chemical reaction cleaves the double bonds in these unsaturated fatty acids. This, in turn, alters cell permeability, thus lysing the cells and, thereby, achieving a bactericidal effect. O
3
also cleaves the double bonds in the functional groups of the polypeptide chains forming the protein capsids of viruses, thus compromising these barriers and, thereby, achieving a biocidal effect. O
3
is proved to kill on contact pathogenic bacteria of the genuses Escherichia (meningitis), Salmonellas (typhoid fever), Legionella (Legionnaire's disease), Streptococcus (bacterial pneumonia, septicemia, endocarditis, scarlet fever) Vibrio (cholera), influenza viruses, polio viruses, various fungi and other parasites, like the amoebas and other protozoans and their cysts (malaria, sleeping sickness), including crypto sporidium. O
3
is known to kill parasites as large as nematodes or round worms, including enterobius vermicularis (pin worms) and
Trichinella spiralis
(trichinosis). O
3
eliminates pathogenic bacteria and viruses from water 3,125 times more rapidly than Cl (chlorine). Moreover, unlike Cl, O
3
does not leave carcinogenic residues that impart a characteristically unpleasant taste and odor to the water.
The city of Nice, France built the first plant for purifying municipal water supplies by ozonation in 1906. Some 2000 such water treatment plants now exist worldwide. They are particularly common in land scarce Western Europe where unlike in the U.S., large acreages are not available for the simpler and less costly sand filtration of waste water during its tertiary treatment for reuse as potable supply. The first ozone plant to control sewage odors was built in New York City in the 1930's.
The basic problem with achieving the sterilization of objects through ozone treatment is no different than the basic problem with achieving sterilization through other antimicrobial agents like moist heat, dry heat, ethylene oxide (normally mixed with CO
2
or rare gases to minimize explosion hazard) and other gases, and liquid chemicals. The problem is one of distribution. To be a sterilant, the agent must be distributed in lethal quantity to all inoculum on the object to be sterilized. In limited circumstance, this problem has been overcome with moist and dry heat and ethylene oxide gas.
For example, moist heat at 250° F. will kill even the hardy
B.stearothermopilus
endospores in less than 1 hour. The destruction of these heat resistant spores is a gold standard for evaluating the effectiveness of heat sterilizers. If these endospores, the most heat resistant of all known microbes are killed, it can be assumed that all other bacteria and the much smaller viruses (including HIV and Hepatitis) are also dead. Given sufficient time, continuously generated moist heat will distribute to all inoculum by forced convection and thermal conduction. With steam, these distribution methods are aided by condensation and release of the latent heat of vaporization. Steam with a temperature of at least 250° F. can be generated under pressure in an autoclave. After approximately 30 minutes, heat from the 250° F. pressurized steam will distribute to all inoculum on an oven's contents, including
B.Stearothermopolis
endospores, and kill them. After several hours, often overnight treatment, the sporicidal chemical ethylene oxide gas, sometimes under pressure and/or at slightly elevated temperature (120° F. to 140° F.), will distribute to all inoculum on a chamber's contents, including
B.Stearothermopolis
endospores, and kill them.
The problem with distributing ozone to sterilize has not been so easy to resolve, even in limited circumstances. This highly unstable molecule quickly breaks down in atmosphere to form O
2
. O
3
is subject to unimolecular reaction. An ozone molecule O
3
, which is energetically excited by, for example, molecular collision, absorbing a photon, or heating, spontaneously decomposes to dioxygen and atomic oxygen. At room temperature, surface reactions appear most responsible for the decomposition of O
3
. The half life of the O
3
molecule, even in dry atmosphere, is a mere 20 to 100 minutes, normally about 30 minutes, and this short half life is quite adversely affected by moderately increased temperature and humidity. Thermal decomposition of O
3
has been extensively studied within a range of 80-500° C. O
3
(g) rapidly decomposes at temperatures above 100° C. As little as 0.02-0.03 mg H
2
O per liter of air impairs O
3
yields. The presence of water vapor in an ozone generating cell stimulates the production of nitric acid HNO
3
in lieu of O
3
, thereby, decreasing O
3

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