Ozonator: An ozonator generates ozone, a colorless gas, and diffuses it into the air or water. The chemical reaction that occurs when ozone is created helps to remove pesticides, bacteria, odors, and inorganic and organic compounds from the surrounding environment. As a result, ozonators are commonly used for purification techniques, or to improve the smell or taste of water. Water ozonators are also called ozone generators.
Oxygen and ozone: Oxygen is a chemical element; it is also a gas with no color, taste, or smell. In its most stable form, oxygen's two atoms combine to make dioxygen or O2. Oxygen is much more stable than ozone.
Ozone, also called O3 trioxygen, or activated oxygen, is made up of three oxygen atoms. Ozone exists high in the Earth's atmosphere and absorbs solar radiation. On the planet's surface, however, this same substance is so unstable that there is no effective way to store it. Therefore, ozone reverts quickly back to oxygen once it has been generated. Ozone is harmful in large concentrations, most notably causing damage to the respiratory systems of humans and other living creatures.
Ozone is created when oxygen comes into contact with a high-energy source, such as electricity. Once this contact occurs, the two oxygen molecules are separated. Single oxygen molecules then attach to other double oxygen molecules to create trioxygen, or ozone. For example, ozone may form when solar ultraviolet (UV) radiation interacts with dioxygen in the atmosphere.
Ozone may only last for up to 30 minutes in uncontaminated water and for much shorter time periods in contaminated water. When ozone self-destructs, it releases energy.
Ozone is a powerful oxidizing agent because it gives up oxygen easily. Oxidation occurs when oxygen combines with a substance and triggers a chemical reaction. Oxidation may be used to create fertilizers and cleaning products and also to disinfect substances or to eliminate contaminants. Ozone is 50% more powerful than chlorine when it's used as an oxidizing agent.
The process of producing ozone with electricity is called electrical discharge; it involves sending high-voltage electricity across a small, narrow space that contains filtered air or pure oxygen. A process called "corona discharge" is typically used in larger areas: This method creates a tiny, controlled lightning strike in an enclosed area.
History: The use of ozone to treat drinking water dates back to the late 1800s, when it was first introduced in the Netherlands. Today, ozone is commonly used to treat water in Europe. In the United States, ozone was first used to treat drinking water to improve its color, odor, and taste. After the Surface Water Treatment Rule was passed in 1998, the use of ozone to disinfect water became more widespread.
General use: Ozonated water has a number of industrial and household uses.
Municipal use: Ozone is commonly used in place of chlorine to eliminate bacteria in public water supplies.
Industrial use: Ozone is used to disinfect laundry in many facilities, such as hospitals and nursing homes. It may also be used to clean fruits, vegetables, and other foods, and to clean and disinfect municipal drinking water, spas, pools, and fabrics. Ozonated water is commonly used in aquariums and other aquatic environments. It is also used in a number of chemical processes, such as the making of fertilizer and the manufacture of various cleaning products. Bottlers (e.g., those who sell bottled water or beer) also use ozone as a disinfectant to keep caps, bottles, and related bottling equipment clean.
The U.S. Food and Drug Administration (FDA) has approved ozone for use as a food additive. According to the FDA, ozone is safe to use as an antimicrobial agent in the treatment, storage, and processing of certain foods; these foods include meats, seafood, and vegetables when they are processed under specific, prescribed conditions.
Water in swimming pools at the 2008 Summer Olympic Games in Beijing, China was treated with ozone technology instead of chlorine; chlorine is a chemical that may be harmful to the lungs, eyes, and skin. Ozone from ambient air and pure oxygen was metered into the water to disinfect it.
Household use: Ozonated water may be used to sanitize clothing, foods (such as vegetables and meats), drinking water, and surfaces like kitchen counters. It is also used to eliminate bacteria in hot tubs and personal spas. There is currently no standard to help consumers understand the power or level of ozonation necessary when buying a water ozonator. Manufacturers state that the power of the unit and the level of ozonation depends on the consumer's planned use (i.e., which substances the consumer is trying to eliminate).
Manufacturers also promote household devices that purify the air by emitting ozone. Some companies claim that these emissions cleanse and sanitize both the air and various surfaces in homes. However, the U.S. Environmental Protection Agency (EPA) states that this process may not effectively kill viruses or strip the air of chemicals, unless it is done at levels that are hazardous to humans.
Medicinal use: Reports of using ozone for medicinal purposes date back to the late 19th Century. In modern times, ozone therapists have used different forms of ozone to treat a wide variety of conditions. There has been little scientific study, however, of ozone therapy in humans. Some marketers claim that ozonated water may kill bacteria that cause bad breath. They also claim that their devices may be used to add ozone to oils (such as safflower and olive oils): These ozonated oils may help to ease skin inflammation and heal skin disorders when they are used topically.
General: Ozone kills bacteria and eliminates other contaminants when its components split up and revert back to oxygen. When ozone breaks apart into three separate oxygen atoms, two atoms join together to form dioxygen; the third atom seeks particles in water (such as bacteria or pesticides) and disintegrates.
Water ozonators are used by municipalities to disinfect drinking water, to eliminate odors, and to ensure that their water has a high-quality taste. Consumers may buy household water ozonators to disinfect foods during meal preparation and to clean kitchen surfaces.
Researchers indicate that some pesticides and synthetic chemicals cannot be removed from water through the ozonation process. In addition, "hard" water (created by the addition of the minerals magnesium and calcium to water) cannot be improved (softened) through ozonation.
Industrial and large-scale use: For large-scale use, ozone may be added to water in three different ways: A turbine may be used to combine ozone with air and to propel this gaseous mixture into the water; a pump may be used as a conduit to bring ozone to the water's source; or ozone may be pumped into the water through a diffuser or air stone. Ozone must be added in specific concentrations and quantities and kept in the water for a sufficient amount of time in order to be effective. The specific amounts depend on the size of the water vessel and the intended goal of ozonation.
Household use: Household water ozonators are available in a range of sizes. Some machines are designed to sit on countertops, while others may be mounted to walls. These devices are intended to ozonate small quantities of water for use in liter bottles or five-gallon tanks. Larger devices may also be connected under the kitchen sink for continual treatment of water as it flows to the kitchen tap. Still-larger devices may be connected to a home's incoming water supply to ozonate all household water.
Water ozonators are powered by electricity. Some ozonators may be small enough to plug into standard electrical outlets within the users' homes.
Water ozonators produce varying amounts of ozone based on their power output. Power is indicated by "ozone output." Smaller or less powerful devices may produce 300 milligrams (mg) of pure ozone per hour. Larger water ozonators that are installed under a kitchen sink for household use may produce 1,800mg of ozone per hour; an ozonator designed to purify all incoming household water may produce up to 5,600mg of ozone per hour.
When a water ozonator is activated, the electricity-powered device turns air into ozone. Some machines use ultraviolet D (UVD) light rays to provide the energy that transforms oxygen to ozone; others use a process called "corona discharge," which is similar to producing a miniature lightning bolt inside the device. Depending on the type of equipment, voltage may be boosted anywhere from 800 to 20,000 volts across a gap. When oxygen passes through the gap, it is "zapped" by the high voltage, becomes ozone and is sent through a tube. The ozone is then pushed out with an injector and a pump (similar to a swimming pool pump), or through a diffusing rock that "bubbles" the ozone into the water through a thin tube into a water container. Water containers are typically sold separately.
The length of time that it takes to purify water depends on the power of the device and on the amount of water to be treated. One manufacturer claims that one of its devices is able to purify a gallon of water in 15 minutes.
Some water ozonators are designed to disinfect water and foods, such as meats, seafood, vegetables, and fruits. For some of these devices, food is placed into a container of water, and ozone is bubbled through the water for a specified amount of time.
Manufacturers often claim that ozonated water may be placed in a spray bottle and used to disinfect and clean surfaces, such as kitchen countertops.
Water ozonators need to be maintained on a regular schedule. For example, some ozonators contain cartridges that dry air as it enters the device; they may also include an air filter. Both the filter and the cartridge need to be changed periodically, according to the manufacturer's instructions.
Experts recommend filtering ozonated water. After ozonation, filtration removes any substances and particulate matter that has been "killed" through the purification process.
Ozonation is commonly used to disinfect public water supplies in Europe, but this purification process is less popular in the United States. The U.S. Environmental Protection Agency (EPA) has reported, however, that the number of ozone-using water treatment facilities in the United States underwent an increase from 40 plants in 1991 to 264 facilities by 1998.
Ozonation is used in the United States to purify commercially-bottled water, and it is used industrially to clean foods, such as vegetables and meats. It is also used to disinfect commercial laundry, to clean boats, buildings, fabrics, swimming pools, spas, wood and paper products, and objects that have been damaged by fire,
Ozonation may be used to remove endocrine-disrupting compounds (EDCs), pharmaceuticals, and personal care products from drinking water. EDCs are a group of chemicals that may affect the hormone functions of humans and wildlife. EDCs that are commonly found in drinking water include atenolol, atrazine, carbamazepine, estrone, gemfibrozil, meprobamate, naproxen, phenytoin, sulfamethoxazole, TCEP, and trimethoprim. Even in very small amounts, these chemicals may threaten ecosystems, aquatic life, and human health.
U.S. Food and Drug Administration (FDA) regulations now allow the use of ozone to kill microbes and to sanitize foods, such as vegetables, seafood, and meats. Using an ozone water wash on foods may help to keep fruits (such as oranges, pears, apples, grapes, and berries) fresh for an extended period of time. Also, some findings suggest that cleaning seafood with ozonated water may help to keep these products fresh for an additional five days. This preservation effect occurs when ethylene is oxidated, slowing the ripening process; the process also causes the destruction of microbes.
In 2002, researchers investigated the possible use of ozone as a germicide for harvested foods and in food processing, with the goal of making foods safer for consumers by reducing pathogens. Researchers concluded that ozone may be an effective sanitizer for surfaces, such as counters and mats for food processors. They noted that it may take multiple rinses or applications of ozonated water for the complete sanitization of some pathogens. It was suggested that a safe level of ozone in water may be 0.1-2.0 parts per million; exceeding this amount may result in excessive off-gassing (gas that is released into the air as a result of chemical use). Off-gassing may be harmful to food processing workers.
Ozonated water may be used in combination with other purification processes (such as the application of ultraviolet C light) to sanitize vegetables in the food processing industry.
In 2007, researchers tested fresh water from a Swiss lake to compare the effectiveness of different cyanotoxin removal methods; cyanotoxins are toxic materials created during algae blooms, which may be lethal to humans and animals. Ozone was best able to oxidize all three investigated cyanotoxins. The researchers also noted the presence of harmful byproducts that were associated with the chlorine treatment of water.
A major benefit to the ozonation of water is that it significantly reduces the amount of chlorine needed for the disinfection process. Viruses and microbial agents may be wiped out by much smaller amounts of ozone than chlorine, without the associated health risks. Consuming water with specific amounts of chlorine has been shown to lead to developmental and reproductive problems; it may also be associated with an increased risk for cancers of the bladder, colon, and rectum. Chlorine levels in public water supplies must be carefully monitored, and must not exceed safety levels set by the U.S. Environmental Protection Agency (EPA).
Research conducted in 2009 documented safety issues that may result from the ozonation of municipal drinking water; specifically, there was concern over the production of the chemical bromate (a common by-product of the ozonation process). Exposure to bromate has been associated with changes in the genes and proteins of rats. In previous research, bromate has also been associated with kidney damage in humans and animals, and with cancer in animals. The EPA requires that water treatment facilities routinely test their water supplies to ensure that bromate levels do not exceed the allowable amount.
Scientists note that a small number of pesticides, organic substances (any substance that contains carbon), and inorganic substances (minerals, for example) may become more toxic or harmful when they are oxidized by, for example, the addition of ozone. Impurities such as bromine in water may also be harmful, but in many cases another treatment process is able to remove them.
Government specified exposure levels for ozone have been set for industrial use: Workers may not be safe when exposed to air that contains more than 0.0002 grams of ozone per cubic meter over an eight-hour shift.
Adequate ventilation must be provided to workers in the food processing industry, so that toxic vapors created by the use of ozone do not collect in a concentrated space.
High concentrations of ozone have been found to burn mucous linings in the human nose. Long-term consequences of this destructive exposure have not been studied.
Drinking ozonated water is considered to be a type of ozone therapy. Some health professionals support these therapies, but many argue that there is no scientific evidence to support the health-related benefits of ozonated water. Experts do not recommend that patients rely on ozone therapies alone to treat potentially-dangerous medical conditions.
FUTURE RESEARCH OR APPLICATIONS
Some water technology companies see the growth of water ozonation as a "green," non-polluting method of cleaning and disinfecting various products. The process may be used in a variety of industries, from commercial laundries to food service.
Manufacturers of ozonated water continue to find new applications for their product; its use is currently being refined in the beverage industries, on fish and seafood farms, in swimming and spa facilities, within commercial laundries, in the agriculture/food processing industries, in the treatment of drinking water, and as part of the treatment of industrially-discharged water.
Studies continue to examine ozonated water washes as an effective way to disinfect food for human consumption without using chlorine. Food industry representatives predict an increase in the use of ozonated water for the disinfection of produce and for the cleaning of food preparation surfaces.
Some experts predict that water regulations will become more stringent. This regulatory environment will, in turn, help to fuel an expanded market for ozonation in the treatment of waste water and drinking water.
Researchers see promise for a new technique that may treat water by combining ozonation with ultraviolet (UV) radiation.
Companies that need to handle or dispose of their wastes and by-products may eventually adopt water-ozonation techniques: In theory, ozonation could handle the job without the use of additional "clean-up" chemicals.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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