ABSTRACT
Chlorine dioxide is a relatively small, volatile and highly energetic molecule which is also a free radical. There is a lower oxidant demand for chlorine dioxide than for chlorine. This is an indication that chlorine dioxide is more selective and less reactive than chlorine. One can see that chlorine dioxide may be generated by reducing sodium chlorate or by oxidizing sodium chlorite. It is also apparent that the ultimate destiny of any chlorine species is the humble chloride ion, the lowest energy reservoir of all. Chlorine dioxide disinfects by oxidation. The use of chlorine dioxide as a fmal disinfectant is somewhat limited because of its contributions to taste and odor problems when distribution system residuals exceed 0.5 ppm. For drinking water treatment, chlorine dioxide is generated and used only in aqueous solutions. Commercial chlorine dioxide generators for drinking water applications typically produce aqueous concentrations of 3 g/L or below, and treatment levels generally range from 0.1 mg/L to 3.0 mg/L.
