Abstract
A geometric model is proposed herein to quantify relationship between diffusion coefficient within biofilm and dry density of biofilm. This model describes a tortuosity structure of porosity in biofilm consisting of either bacillary cells or spherical cells. Nitrite diffusion coefficients in seven kinds of particles layers, which consisted of glass beads or vinylon fibers, were measured for verification of the model proposed. The results of the experiment gave good agreement with the theoretical values estimated by the model. The diffusion coefficient in the particles layers estimated from the model was affected neither by particle size nor by the difference in shape between spherical and bacillary at a porosity above about 0.3. The model predicts that diffusion coefficient within biofilm decreases with increasing biofilm density, leading to about 80% of that in water when the dry density is 25g·l-1.
