Principles Of Ozone Effluent Treatment

Ozone was first discovered by the Dutch philosopher Van Marun in 1785. In 1840, Schonbein reported and named ozone from the Greek word ozein, meaning to smell. The earliest use of ozone as a germicide occurred in France in 1886, when de Meritens demonstrated that diluted ozonized air could sterilize polluted water. In 1893, the first drinking water treatment plant to use ozone was constructed in Oudshorrn, Holland. Other plants quickly followed at Wiesbaden (1901) and Paderborn (1902) in Germany. In 1906, a plant in Nice, France, was constructed using ozone for disinfection. Today, there are over 1,000 drinking water treatment plants in Europe utilizing ozone for one or more purposes. In the United States, the first ozonation plant was constructed in Whiting, Indiana, in 1941 for taste and odor control.

Over 100 years ago it had been demonstrated that ozone (03), the unstable triatomic allotrope of oxygen, could destroy molds and bacteria and by 1892 several experimental ozone plants were in operation in Europe. In the 1920s, however, as a result of wartime research, during World War I, chlorine became readily available and inexpensive, and began to displace ozone as a purifier in municipalities throughout the United States. Most ozone studies and development were dropped at this time, leaving ozonation techniques, equipment, and research at a primitive stage. Ozone technology stagnated, and the development and acceptance of ozone for water and wastewater treatment was discontinued. In addition to the popular use of chlorination as a wastewater disinfectant and the consequent technology lag in ozonation research, there was a third impediment to ozone commercialization: the comparatively high cost of ozonation in relation to chlorination. Ozone's instability requires on-site generation for each application, rather than centralized generation and distribution. This results in higher capital requirements, aggravated by a comparatively large electrical energy requirement. Ozone's low solubility in water and the generation of low concentrations, even under ideal conditions, also necessitates more elaborate and expensive contacting and recycling systems than chlorination.

In spite of such obstacles there is interest from time to time in the use of ozone, particularly for wastewater treatment. The technology for the destruction of organics and inorganics in water has not kept pace with the increasingly more sophisticated water pollution problems arising from greater loads, new products, and new sources of pollutant entry into the environment and increased regulation. The growing trend toward water reuse and the fact that some highly toxic pollutants may be refractory to conventional treatment methods has spurred investigation into new treatments, including ozonation.

A significant impetus from time to time for developing new methods is dissatisfaction with chlorination. Chlorine affects taste and odor and produces chloramines and a wide variety of other potentially hazardous chlorinated compounds in wastewaters. It seriously threatens the environment with an estimated 1,000 tons per year of chlorinated organic compounds discharged into U.S. waters (chloramines are not easily degradable and pose a hazard to the environment) and is questionable as a drinking water viricidal disinfectant. Ozone's development, on the other hand, could parallel a greater environmental awareness and a resulting demand for higher-quality effluents, as its potential for overcoming these problems is possible.

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