Sterilization of water

Ozone can also be used as an oxidizing agent, but because of its instability, it must be generated on-site. It is a powerful oxidant for some organic materials, but others are oxidized only slowly or not at all. Ozone is only suitable for low concentrations of oxidizable materials. A common use is for the sterilization of water. 

Guinvarc h, P. Three years of ozone sterilization of water in Paris. Adv. Chem. Set. 21 416-429, 1957. 

Chlorine occurs mainly in seawater, in which chloride is the most abundant anion (19350 mg kg-1), and as rock salt (halite, NaCl) in evaporites. Elemental chlorine is important in sterilization of water supplies and production of chlorinated plastics such as polyvinyl chloride (PVC), but some chlorine compounds used extensively in the past, such as the insecticide... 

It is interesting to note that ozone is the subject today of many discussions in relation with environmental concerns. However, this gas remains an important chemical reagent in industrial areas like the sterilization of water or the bleaching of wood pulp [1],... 

The product is shipped in tank cars or in glass carboys. The solution must be stored cold and protected from sunlight. It is used for bleaching vegetable fibres, in laundries and textil factories. This hypochlorite solution is also used for the sterilization of water. 

Three Years of Ozone Sterilization of Water in Paris... 

In 1904 the city of Nice, authorized by the French Higher Council of Public Hygiene, adopted ozone, and 2 years later the sterilization of water by ozone was put in practice on an industrial scale for the first time in France. Since then, numerous towns have followed the example of Nice. 

Ozone can be used to replace chlorine for the sterilization of water. Replacement of chlorine is desirable because chlorination increases the salinity of water. The more salt in the water the less value it has for later use in, for example, irrigation of cropland. When used to sterilize water, chlorine reacts with trace organic compounds to form carcinogenic chlorine compounds such as chloroform. The use of ozone to replace chlorine in water treatment will eliminate chlorination-induced salinity and carcinogenic chlorinated organic compounds. Because of its instability, any residual ozone not consumed in purifying the water rapidly decomposes to ordinary oxygen. 

In some cases, reverse osmosis is applied, and this removes almost all the particulates and organic materials, as well as microorganisms and endotoxins. Electrodeionization, which combines ion exchange membranes and resins, removes the last traces of dissolved ions from water under influence of a direct electric current. The last stage of the purification is ozone sterilization of water to inactivate residual microorganisms, as ozone is an efficient disinfectant (UV at 254 nm wavelength is then used to break up the spent ozone). The PW generated is then circulated to each point where it is used (point of use POU). 

Water treatment Desalination of saline water to produce drinking water, removal of nitrate ions from groundwater,21 sterilization of water.22... 

PLASMA CLEANING AND STERILIZATION OF WATER SPECIAL DISCHARGES IN LIQUID WATER APPLIED FOR ITS CLEANING AND STERILIZATION... 

Development of small but sophisticated systems for electrochemical generation of hypochlorite from very dilute solutions of NaCl is of present interest. In recent years, electrochemical synthesis of extra-pure sodium hypochlorite solutions for medical use has received growing attention [84,85]. The electrolytic solution is an isotonic physiological salt solution containing 0.89% NaCl. Another application is the disinfection of drinking water that contains only 10-100 mg NaCl per liter [86,87]. Reviews of onsite generation of hypochlorite for water treatment and of the sterilization of water and wastewater include those of Michalek and Leitz [56] and, more recently, Scott [88]. 

Thus, the created devices allow us to remove impurities from treated water, which belong to different classes in accordance with their dispersion degree, origin, and nature. Finite sterilization of water can be carried out by ultraviolet using bactericidal bulbs of suitable capacity. The different processes of impurities removal through the created devices are illustrated in Figure 8.15. 

The last decade has seen the introduction of a number of small electrolysis cells for the generation of either hypochlorite or chlorine gas in many applications, either type of cell could, in principle, be employed and the choice will then depend on technological factors. In the water and effluent-treatment industry, the common applications of on-site chlorine and hypochlorite cells will include the treatment of sewage (particularly at remote sites), the sterilization of water for food processes and hospital laundries, the treatment of water on board ships and for swimming pools, the treatment of cooling water at coastal power stations to prevent the growth of shellfish and seaweed in the pipes and the enhanced... 

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