Indirect Determination of Ozone Mass Transfer Coefficients

4 Indirect Determination of Ozone Mass Transfer Coefficients 

Oxygen transfer measurements can be used to obtain kLa 03) and sometimes it is the only method available. In such cases, the ratio of the diffusion coefficients from equation 3-29 is employed  

Using experimentally determined values of the diffusion coefficients for ozone (03) = 1.26 10 9 m2 s 1 (Matrozov et al., 1978) and oxygen D(02) = 2.025 10 9 m2 s 1 (St. Denis, 1971) results in the above factor of 0.622 for n = 1. The power can vary from 0.5 to 1.0 depending on the hydrodynamic conditions in the reactor as discussed in Section 3.2, For ozonation in bubble columns, n is generally assumed to be 1.0. The diffusion coefficients are valid for the system lgas/(clean) water at T = 20 °C. 

Other values for D(03) and D(02) can be found in the literature, and depending on which ones are used the factor can vary considerably. For example, using diffusion coefficients for ozone derived from theoretical considerations, e. g. Wilke and Chang (1955) or Scheibel (1958) (cited by Reid et al. (1977), with the same D(02) as mentioned above will result in seriously different factors for D(03)/D(02) (0.864 and 0.899 respectively) and would thus result in different values for kLa(Of). 

Based on these considerations, it is preferable to perform mass transfer measurements using ozone whenever possible. The measurements should be conducted with the same water or waste water and under the same range of operating parameters in which the oxida- 

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