So lets ask, what are the disinfection applications of chlorine dioxide?
The biochemical effect on bacteria and viruses, is based on causing damage to the cell membranes and disrupting and/or interrupting metabolic processes.
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. As well as a range of sodium chlorite products for the home!
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 (ClO3). In the second stage chlorine dioxide accepts 4 electrons and forms chloride (Cl-). In the water some chlorate (ClO3), 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 1950'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 (ClO2-), 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.