Bleaching Chlorine dioxide is sometimes used for bleaching of wood pulp in combination with chlorine, but it is used alone in ECF (elemental chlorine-free) bleaching sequences. It is used at moderately acidic pH (3.5 to 6). The use of chlorine dioxide minimizes the amount of organochlorine compounds produced.Chlorine dioxide (ECF technology) currently is the most important bleaching method worldwide. About 95% of all bleached Kraft pulp is made using chlorine dioxide in ECF bleaching sequences.Chlorine dioxide is also used for the bleaching of flour. Water chlorination The Niagara Falls, New York, water treatment plant first used chlorine dioxide for drinking water treatment in 1944 for phenol destruction.Chlorine dioxide was introduced as a drinking water disinfectant on a large scale in 1956, when Brussels, Belgium, changed from chlorine to chlorine dioxide.Its most common use in water treatment is as a pre-oxidant prior to chlorination of drinking water to destroy natural water impurities that would otherwise produce trihalomethanes on exposure to free chlorine.Trihalomethanes are suspect carcinogenic disinfection by-products associated with chlorination of naturally occurring organics in the raw water.Chlorine dioxide is also superior to chlorine when operating above pH 7,in the presence of ammonia and amines[citation needed] and/or for the control of biofilms in water distribution systems. Chlorine dioxide is used in many industrial water treatment applications as a biocide including cooling towers, process water, and food processing. Chlorine dioxide is less corrosive than chlorine and superior for the control of legionella bacteria.Chlorine dioxide is superior to some other secondary water disinfection methods in that chlorine dioxide: 1) is an EPA registered biocide, 2) is not negatively impacted by pH, 3) does not lose efficacy over time (the bacteria will not grow resistant to it) and 4) is not negatively impacted by silica and phosphate, which are commonly used potable water corrosion inhibitors. It is more effective as a disinfectant than chlorine in most circumstances against waterborne pathogenic microbes such as viruses[clarify], bacteria and protozoa – including the cysts of Giardia and the oocysts of Cryptosporidium. The use of chlorine dioxide in water treatment leads to the formation of the by-product chlorite, which is currently limited to a maximum of 1 ppm in drinking water in the USA.:4–33 This EPA standard limits the use of chlorine dioxide in the USA to relatively high-quality water[why?], or water that is to be treated with iron-based coagulants (iron can reduce chlorite to chloride).[citation needed] Chlorine dioxide has many applications as an oxidizer or disinfectant. Chlorine dioxide can be used for air disinfection[24] and was the principal agent used in the decontamination of buildings in the United States after the 2001 anthrax attacks. After the disaster of Hurricane Katrina in New Orleans, Louisiana, and the surrounding Gulf Coast, chlorine dioxide has been used to eradicate dangerous mold from houses inundated by the flood water.Because of its unique qualities, chlorine dioxide is an effective disinfectant even at low concentrations. Article From https://en.wikipedia.org/wiki/Chlorine_dioxide#Uses