When added to drinking water, it helps destroy bacteria, viruses and some types of parasites that can make people sick, such as Cryptosporidium parvum and Giardia lamblia. The Environmental Protection Agency EPA regulates the maximum concentration of chlorine dioxide in drinking water to be no greater than 0. Chlorine dioxide chemistry is used in a wide variety of industrial, oil and gas, food and municipal applications:.
Food and Beverage Production Chlorine dioxide can be used as an antimicrobial agent in water used in poultry processing and to wash fruits and vegetables.
Paper Processing Chlorine dioxide is used to chemically process wood pulp for paper manufacturing. Medical Applications In hospitals and other healthcare environments , chlorine dioxide gas helps to sterilize medical and laboratory equipment, surfaces, rooms and tools. Researchers have found that at appropriate concentrations, chlorine dioxide is both safe and effective at helping to eliminate Legionella bacteria in hospital environments.
Chlorine dioxide is not a cure or treatment for medical ailments, including but not limited to autism, HIV, malaria, hepatitis viruses, influenza, common colds, and cancer. The U. Chlorine dioxide solution is a diluted version of sodium chlorite. When citric acid is added, the mixture becomes chlorine dioxide a powerful bleaching agent. Both sodium chlorite and chlorine dioxide are the active ingredients in disinfectants and have additional industry uses.
They are not meant to be ingested. They are often referred to as MMS. Additionally chlorine dioxide does not produce large amounts of aldehydes, ketons, keton acids or other disinfection byproducts that originate from the ozonisation of organic substances. Drinking water treatment is the main application of disinfection by chlorine dioxide.
Thanks to its adequate biocidal abilities, chlorine dioxide is also used in other branches of industry today. Example are sewage water disinfection, industrial process water treatment, cooling tower water disinfection, industrial air treatment, mussel control, foodstuffs production and treatment, industrial waste oxidation and gas sterilization of medical equipment. How does chlorine dioxide disinfect?
Chlorine dioxide disinfects through oxidation. It is the only biocide that is a molecular free radical. It has 19 electrons and has a preference for substances that give off or take up an electron. Chlorine dioxide only reacts with substances that give off an electron. Chlorine, oppositely, adds a chlorine atom to or substitutes a chlorine atom from the substance it reacts with.
How does disinfection by chlorine dioxide work? Substances of organic nature in bacterial cells react with chlorine dioxide, causing several cellular processes to be interrupted. Chlorine dioxide reacts directly with amino acids and the RNA in the cell. It is not clear whether chlorine dioxide attacks the cell structure or the acids inside the cell. The production of proteins is prevented. Chlorine dioxide affects the cell membrane by changing membrane proteins and fats and by prevention of inhalation.
When bacteria are eliminated, the cell wall is penetrated by chlorine dioxide. Viruses are eliminated in a different way; chlorine dioxide reacts with peptone, a water-soluble substance that originates from hydrolisis of proteins to amino acids.
Chlorine dioxide kills viruses by prevention of protein formation. Chlorine dioxide is more effective against viruses than chlorine or ozone.
Can chlorine dioxide be used against protozoan parasites? Chlorine dioxide is one of a number of disinfectants that are effective against Giardia Lambia and Cryptosporidium parasites, which are found in drinking water and induce diseases called 'giardiasis' and 'cryptosporidiosis'. The best protection against protozoan parasites such as these is disinfection by a combination of ozone and chlorine dioxide.
Can microorganisms become resistant against chlorine dioxide? Chlorine dioxide as a disinfectant has the advantage that it directly reacts with the cell wall of microorganisms. This reaction is not dependent on reaction time or concentration. In contrast to non-oxidizing disinfectants, chlorine dioxide kills microorganisms even when they are inactive.
Therefore the chlorine dioxide concentration needed to effectively kill microorganisms is lower than non-oxidizing disinfectant concentrations. Microorganisms cannot built up any resistance against chlorine dioxide. Can chlorine dioxide be used against bio film? Chlorine dioxide remains gaseous in solution. The chlorine dioxide molecule is powerful and has the ability to go through the entire system. Chlorine dioxide can penetrate the slime layers of bacteria, because chlorine dioxide easily dissolves, even in hydrocarbons and emulsions.
Chlorine dioxide oxidizes the polysaccharide matrix that keeps the bio film together. During this reaction chlorine dioxide is reduced to chlorite ions. These are divided up into pieces of bio film that remain steady. When the bio film starts to grow again, an acid environment is formed and the chlorite ions are transformed into chlorine dioxide.
This chlorine dioxide removes the remaining bio film. What are the disinfection byproducts of chlorine dioxide? The reaction process of chlorine dioxide with bacteria and other substances takes place in two steps.
During this process disinfection byproducts are formed that remain in the water. In the first stage the chlorine dioxide molecule accepts an electron and chlorite is formed ClO 3.
In the second stage chlorine dioxide accepts 4 electrons and forms chloride Cl -. In the water some chlorate ClO 3 , which is formed by the production of chlorine dioxide, can also be found.
Both chlorate and chlorite are oxidizing agents. Chlorine dioxide, chlorate and chlorite dissociate into sodium chloride NaCl. Can chlorine dioxide be used to disinfect drinking water? In the 's the biocidal capability of chlorine dioxide, especially at high pH values, was known. For drinking water treatment it was primary used to remove inorganic components, for example manganese and iron , to remove tastes and odors and to reduce chlorine related disinfection byproducts.
For drinking water treatment chlorine dioxide can be used both as a disinfectant and as an oxidizing agent. It can be used for both pre-oxidation and post-oxidation steps. By adding chlorine dioxide in the pre- oxidation stage of surface water treatment, the growth of algae and bacteria can be prevented in the following stages. Chlorine dioxide oxidizes floating particles and aids the coagulation process and the removal of turbidity from water.
Chlorine dioxide is a powerful disinfectant for bacteria and viruses. The byproduct, chlorite ClO 2 - , is a weak bactericidal agent. In water chlorine dioxide is active as a biocide for at least 48 hours, its activity probaly outranges that of chlorine.
Chlorine dioxide prevents the growth of bacteria in the drinking water distribution network. It is also active against the formation of bio film in the distribution network.
Bio film is usually hard to defeat. It forms a protective layer over pathogenic microorganisms. Most disinfectants cannot reach those protected pathogens.
However, chlorine dioxide removes bio films and kills pathogenic microorganisms. Chlorine dioxide also prevent bio film formation, because it remains active in the system for a long time.
The result is the replication of the complete virus until the cell bursts; releasing many additional viral particles into the surrounding medium. In the presence of these acidic nucleic acids; the CLO 2 molecule becomes unstable and releases nascent oxygen into the medium.
It is the sequence of these four units along the chain that makes one segment of DNA differs from another. RNA differs chemically from DNA in that the base thymine is replaced by the base uracil U ; representing a very subtle biochemical difference. There is also a subtle difference in the sugar deoxyribose. The release of nascent oxygen from chlorine dioxide CLO 2 in an acidic environment. The base guanine; found in both RNA and DNA; is very sensitive to oxidation; forming 8-oxoguanine as the oxidation product [4].
The release of CLO 2 results in the oxidation of the guanine residue with the formation of 8-oxoguanine; thereby disallowing the replication of the viral nucleic acid by base pairing. Although the replication of the protein coat may continue; the formation of a complete functional virus has been blocked by CLO 2 oxidation.
These bacteria survive only in the absence of oxygen and include many pathogenic organisms. With the appearance of algae; carbon dioxide; present in large proportion in the primordial atmosphere; was converted by algae to carbohydrates; generating oxygen as a by product. At first; oxygen reacted with iron salts in the primitive oceans to generate extensive deposits of iron oxide iron ore. When soluble iron in the oceans became exhausted; oxygen concentration in the atmosphere began to rise. Some bacteria were able to survive the increased levels of oxygen in the atmosphere by any of three paths.
The presence of oxygen in the atmosphere resulting from algae and other plants containing the green pigment chlorophyll; allowed the development of the wide range of life forms both in the ocean and on land known today as animals.
Some anaerobic bacteria took up residence in oxygen-free environments within the bodies of animals; notably; the intestines. Other anaerobes solved the problem of oxygen toxicity by evolving metabolic ways to cope with its universal presence. These include the development of the enzyme superoxide dismutase SOD ; which in its most primitive form; contained iron [5]. Later refinements included the incorporation of manganese in mitochondria and finally; a combination of copper and zinc.
It is widely believed that still another solution to oxygen toxicity lay in the development of organisms that have the ability to utilize oxygen in their metabolism.
These organisms are known today as the aerobes or aerobic bacteria. One form of these organisms may have been the precursor of an inclusion organism found in many animal and human cells known as the mitochondria; having its own circular DNA.
It is well known that cultures of many bacteria become acidic; typically generating lactic; acetic and other simple carboxylic organic acids. The acidic medium surrounding many bacteria triggers the decomposition of CLO 2 and the subsequent liberation of nascent oxygen. Nascent oxygen is a particularly potent oxidizing agent for anaerobic organisms because it is essentially a free radical seeking not one; but two electrons. Anaerobic organisms have not developed adequate defences against the onslaught of oxygen; particularly nascent oxygen; and quickly succumb to its lethal action.
This association is equivalent to the formation of hydrogen — chlorine H — Cl covalent bond. Because of the single electron deficiency of the chlorine atom; only one covalent bond is permitted at any one time. Since the H — Cl bond is stronger the H — O bond of water is almost the strongest bond known than the existing O — Cl covalent bond; the O — Cl bond is disrupted by the ejection of nascent oxygen. This leads to the dissociation of the acidic proton from chlorine and the formation of the hypochlorous ion ClO- and sodium hypochlorite NaOCl and the release of nascent oxygen from chlorine dioxide in an acidic environment.
The decomposition of sodium chlorite to nascent oxygen and sodium hypochlorite in an acidic environment. Figure 3 The formula for decomposition of sodium chlorite to nascent oxygen and sodium hypochlorite in an acidic environment]. During World War I; this instability of chlorite ion was exploited by Alexis Carrel —; Nobel laureate ; best known for his prolonged culture of chicken heart cells at Rockefeller University; New York.
Carrel sucessfully administered a crude solution topically to war casualties having embedded shell fragments [6]. The anaerobic organisms responsible for gas gangrene in these wounds were quickly quenched; saving many soldiers that would have otherwise perished [7]. There are only a small number of basic biological substances found in living organisms.
These include proteins; lipids; carbohydrates and nucleic acids. The ability of nucleic acids in the form of viruses to activate chlorine dioxide and then nascent oxygen has been discussed previously. Lipids and carbohydrates are both neutral substances; carrying neither an electric charge nor acidic groups. The possibility of proteins activating CLO 2 is discussed below.
Many proteins; particularly those that are soluble and found free in both the blood and in the medium surrounding tissues; contain on their surfaces organic groups; both acidic and basic alkaline in nature. In most soluble globular proteins either one or the other of these two types of groups predominate. Proteins in which the acidic groups outweigh the basic groups are acidic proteins and those in which the basic groups predominate are known as basic proteins.
A technique has been developed to determine; for a given protein; in which category it may lie. Either acidic or basic proteins migrate under the influence of an applied electric field. This laboratory technique; known as electrophoresis; has been used to determine the acidity or basicity of proteins.
As the pH of the surrounding medium into which a protein has been solubilized is changed; the protein will migrate either in one direction or the other. When a pH is found that will result in no migration; the protein is said to be at its isoelectric point. The pH value at which this occurs for a given protein is known as the isoelectric point of that protein. The isoelectric points of most proteins are not far from 7 or neutrality. Such proteins are not capable of activating CLO 2 to decomposition; partly accounting for low toxicity.
Fungi are considered as plants without chlorophyll and lack the ability to generate carbohydrates from sunlight and carbon dioxide. They were probably derived in an oxygen-free atmosphere but some have developed the ability to tolerate low levels of oxygen. Most fungi prefer an oxygen-poor environment and live best under these conditions. They obtain their energy requirements from the decomposition through enzyme activity of existing organic matter and; in this light; may be considered as parasitic.
Because of their low tolerance for nascent oxygen and the acidic medium in which they thrive from the liberation of organic acids ; fungi in the mycelial form are sensitive to the destructive action of CLO 2.
One example of a human pathogenic fungus is Candida albicans; invading finger and toenails. From all of the above considerations; it is apparent that CLO 2 is essentially activated only by viruses; acidic bacteria and fungi. Another agent also providing active oxygen is hydrogen peroxide; which has been used in the treatment of arthritis; cancer and other metabolic diseases.
Hydrogen peroxide is commercially available in low concentrations for the treatment of topical microbial infections. Found to be more effective as a sporicide than as a bactericide; hydrogen peroxide is bacteriostatic at concentrations greater than 0. This bonding is unstable; decomposing to acetic acid and one atom of oxygen is being made available as bactericidal; fungicidal or virucidal. Peracetic acid exhibits rapid activity against spores and yeasts [8]. An anti-microbial agent having chemical similarity to CLO 2 is sodium hypochlorite NaOCI in which only one atom of oxygen is bound to halogen rather than two.
Solutions containing ppm were found effective within 30minutes in decontaminating objects which had been massively contaminated by both gram-positive and gram-negative bacteria and fungi. Drinking water heavily contaminated by a polymicrobial suspension became sterile in 30 minutes by a solution containing 10 ppm of sodium hypochlorite [9].
Still another oxidizing agent having increased application is ozone. Ozone is an unstable gas and is not commercially available but must be generated as required. It has been shown that ozone selectively inhibits the growth of human cancer cells [10].
Under specified conditions cancer cell growth was inhibited more than 90 percent while control cells were inhibited less than 50 percent [11]. These results indicate that cancerous cells; because of their altered oxygen metabolism; are less able to handle the oxidative stress presented by ozone than normal cells. Ozone has also been shown to inactivate polio virus with an effect noticeable after only 0.
Ozone is being used both in Europe and the U. Proof that CLO 2 is cytotoxic to bacteria; fungus and virus clinically is shown by data indicating its effectiveness as a disinfectant outside the body. The chemically related compound sodium per iodate NaIO4 inhibited the virulence; decreased the respiration of and increased the sensitivity to phagocytosis of the common pathogen Listeria monocytogenes [16]. The solution gave complete kill of Staphylococcus aureus; Pseudomonas and Candida albicans spores within 10 minutes.
If used in an ultrasound cleaning device complete killing occurred in less than five minutes [17].
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