STRUCTURE OF RBC BIOFILMS

A laboratory-scale model of a rotating biological contactor (RBC) was used to investigate the variations in the structural features of the biofilms formed in the four consecutive compartments of the model during both the early and late stages of the biofilms' development. Microtome sectioning of biofilms showed that, in the early stages of growth, the biofilms were predominantly occupied by non-filamentous bacteria, and some protozoa were present. However, the biofilms in later stages were mostly filamentous. Biofilm porosity was found to decrease with depth in the biofilm and from one compartment to another, and this decrease was associated with a decrease in pore size. The biofilm porosity/density appeared to be a function of the organic loading. In contrast to biofilms in late-formation stages, the areal distributions of both microorganisms and pores in biofilms in the early stages of development were relatively uniform through the biofilm. Scanning electron examination of RBC biofilms revealed that biofilm surfaces possessed some fractal properties.