[Measurement of the effective diffusion coefficient of dissolved oxygen by microelectrodes]

Mass transfer of oxygen inside biocarrier is a key factor determining the performance of simultaneous nitrification and denitrification. Measurement of the effective diffusion coefficient of dissolved oxygen (DO) in a spherical biocarrier was introduced. Based on a diffusion-reaction model, the effective diffusion coefficient of dissolved oxygen (DO) was calculated by curve-fitting the depth distribution of DO measured by microelectrode. At the filling rate of 25%, simultaneous nitrification and denitrification is achieved in the continuous flow reactor with organic removal loading of 5.6 kg/(m3 x d). The effective diffusivity coefficient of DO is calculated to be 0.017 2 m2/d, which means the turbulence diffusion prevailes against the molecular diffusion inside the biocarrier.