Modeling of Drinking Water Oxidation

Modeling in drinking water applications is largely confined to describing chemical processes. The mathematical models used in this area are based on the reaction rate equation to describe the oxidation of the pollutants, combined with material balances on the reaction system to calculate the concentrations of the oxidants as a function of the water matrix. As noted above, the reaction rate equation is usually simplified to pseudo-first order. This is based on the assumption of steady-state concentrations for ozone and the radicals involved in the indirect reaction. 

The assumption of a steady-state ozone concentration for the direct reaction is based on the relatively large concentration of ozone compared to the micropollutants, which means the change in the ozone concentration over time is negligible. Several authors have shown that the indirect reaction of OH° with organic compounds is pseudo-first order due to the steady-state concentration of the hydroxyl radicals (e. g. Yao and Haag, 1992 von Gunten et al., 1995). Further assumptions are that the concentrations of the intermediates, e. g. 02°, 0,°-, H0,° and organic radicals, are also at steady-state (Peyton, 1992). 

The pseudo-first order reaction rate coefficient is then  

The concentration of ozone is relatively easy to measure, however, the OH-radical concentration must be calculated. It is for this OH° concentration that a diversity of models has been developed. The concentration is influenced by the water matrix, with its initiators and 

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