Determination of diffusion layer thickness on a biofilm

Abstract

This paper has proposed two models to determine the thickness (L_o) of the diffusion layer on the biofilm surface. The first is based on the steady-state organic removal flux in a biofilm reactor, and on the bulk organic concentration when oxygen is not limiting. The model has been verified by the experimental data from a submerged RBC. This mode indicates that organic removal flux increases sharply with a decreasing L_o, especially when it is greater than 50 μm. The second model is developed by establishing a relationship between the average flow shear velocity (U) along the biofilm surface and the L_o value. This model provides a simple way for L_o determination since it only requires the measurement of the U value. A comparison of this model is made with other reponed formulas in the literature. Whenever the U value is above 3 cm/s it has the same trend as reported ones. However, at a lower U, it gives a much gradual increase of L_o as compared to others.