Ozone as a disinfectant

The application of O3 in drinking water treatment is prevalent because of its capability of disinfection and oxidation. Ozone, as a disinfectant, is unstable in water and undergoes reactions with water components, whereas O3 decomposes to OH so that advanced oxidation occurs. Unfortunately, undesired oxidation/ disinfection by-products (DBPs) can be formed from... 

Sheldon BW, Brown AL (1986) Efficacy of ozone as a disinfectant for poultry carcasses and chill water. J Food Sci 51(2) 305-309... 

The actual ozone dose utihzed at a water treatment plant is determined by the quaUty of the raw water (i.e., how much ozone demand will be exerted) and what is the ultimate objective for using ozone. Plants using ozone for iron and manganese oxidation will need to apply a different dose than plants using ozone as a disinfectant for inactivation of protozoans such as Cryptosporidium. 

Disinfeetion. Chlorine, as gaseous chlorine or as the h5rpochlorite ion, is widely used as a disinfectant. However, its use in some cases can lead to the formation of toxic organic chlorides, and the discharge of excess chlorine can be harmful. Ozone as an alternative disinfectant leads to products that have a lower toxic potential. Treatment is enhanced by ultraviolet light. Indeed, disinfection can be achieved by ultravifflet light on its own. 

Ozone is used extensively in Europe to purify water. Ozone, a moleeule eomposed of 3 atoms of oxygen rather than two, is formed by exposing air or oxygen to a high voltage eleetrie are. Ozone is mueh more effective as a disinfectant than... 

Ozone was discovered in 1840 and the structure of the molecule as triatomic oxygen was established in 1872. The first use of ozone was reported at the end of the 19th century—as a disinfectant in many water-treatment plants, hospitals, and research centers such as the University of Paris where the first doctoral thesis on ozonation was presented [36]. Although the number of water-treatment plants using an ozonation step... 

Ozone is a powerful oxidizing agent. In the atmosphere near the surface of the Earth, it is irritating and injurious in concentrations greater than two parts per million. It can be used as a disinfectant and a bleach. 

As indicated in all the previous reactions, an intermediate O is first produced. This is called nascent oxygen and is the one responsible for the potent property of ozone as a strong oxidant and, hence, as a strong disinfectant. 

As illustrated, many surface water schemes employ ozonation as a pre- and/or post-treatment to GAC adsorption (in some instances, the ozonation process is supplanted by chlorination). Ozonation as a pretreatment to carbon adsorption achieves two basic objectives 1) ozone applied in first stage ozonation, as in the Mulheim and Choisy-le-Roi cases described in Table 2, serves as a disinfectant, a dissolved oxygen (D.O.) input to raw waters of low D.O., and as an aid to more efficient flocculation, which means greater removals in the sedimentation step and 2) ozonation has been shown to convert a rmmber of organic compounds which are otherwise resistant to treatment into forms which can be effectively removed in GAC beds, either by direct adsorption or by bio-oxklation [10 ]. A number of other pretreatments have been found to lengthen carbon... 

The quantity of ozone necessary for disinfection of a water supply depends on the quality of the water, in particular its content of substances readily oxidized by ozone. As a rule this quantity should be established by preliminary tests, during which it is ensured that for the few minutes necessary to complete destruction, the ozone content of the water goes no lower than 0.2 mg. per liter. 

Ozone is a strong oxidising agent and it has been used for many years as a disinfectant in drinking water production. Bott [1990] has compared chlorine and ozone in cooling water treatment. Edwards [1983] compares the oxidising power of some common water treatment chemicals and he concludes that ozone is the most powerful. Table 14.12 gives the comparison. Bott and Kaur [1994] have reviewed the use of ozone in water treatment. 

Ozone is used as an oxidizing compound, as a disinfectant for air and water, for bleaching waxes and oil, and in organic synthesis. It occurs in the atmosphere at sea level to about... 

Bromate is a disinfection by-product that is produced from the ozonation of source water that contains naturally occurring bromide, whereas chlorite and chlorate are produced as a result of using chlorine dioxide as a disinfectant. Recently, bromate has become the most important inorganic oxyhalide by-product, and its concentration in drinking water has to be controUed. Another chaUenge is seawater, which represents a vay difficult matrix for the analysis of trace ionic constituents, because chloride, sulfate, and sodium are the primary ions and they are presort at extremely high concentrations. " ... 

Ozone is a strong oxidant used for water treatment and disinfection purposes. In many applications, it replaces chlorine it has the main advantage of avoiding the formation of tmwanted chlorinated byproducts. An increasingly important O3 application is its use as a disinfectant in purified water loops for the pharmaceutical and electronic industries, where extreme standards of purification are needed. Today for most... 

Ozone can be made in the laboratory by passing oxygen gas between high-voltage electrodes. It is used as a disinfectant for air and water and as bleach for textiles. 

Disinfection of water supplies commonly uses oxidizing agents such as chlorine or ozone to kill microbial pathogens (bacteria and viruses). Chlorine gas forms chloric(i), HOCl, acid in water. The chlorate (i) ions, CIO, formed in water are responsible for its germicidal properties. Use of chlorine as a disinfectant is of concern due to its ability to oxidize other species, forming harmful by-products (for example, trichloromethane, CHCI3). 

Chlorine dioxide is a selective oxidant and a powerful primary disinfectant. It does not combine with ammonia, like chlorine, so it is useful as a disinfectant when ammonia is present. The use of chlorine dioxide instead of chlorine results in fewer chlorinated by-products. And it does not form bromate like ozone. It does, however, produce chlorite as a reaction product, and this substance is regulated (maximum contaminant level [MCL] 1.0 mg/L). Therefore, the dosage of chlorine dioxide is controlled (maximum residual 0.8 mg/L), thus limiting producing chlorite from this source. 

Ozone is sometimes used as a disinfectant in place of chlorine, particularly in Europe. Figure 13.10 shows the main components of an ozone water treatment system. Basically, air is filtered, cooled, dried, and pressurized, then subjected to an electrical discharge of approximately 20,000 volts. The ozone produced is then pumped into a contact chamber, where water contacts the ozone for 10-15 minutes. 

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