Microbial cells, such as biofilms can be defined as a complex coherent structure of cells and cellular products, like extra-cellular polymers, which either form spontaneously as large, dense granules. The rates and extent of transport of nutrients or metabolites within or through the biofilm are largely dependent on the density and properties of the internal structure. In this study, it has been shown that the biofilm thickness was well developed when the ferrous ion concentration was higher. The higher ferrous ion concentration of butchery waste water make contribution to thick biofilm formation in RBC. Sequencing batch reacter(SBR) studies were carried out in anoxic condition-reduction potential varied from -14 to 17mV for organi matter oxidation with adapted biomass(mixed culture). The well developed thick biofilm sludge showed much higher substrate removal rate than suspended activated sludge. Also, the thick biofilm sludge remove ammonia directly as well as nitrate in anoxic condition. It is supposed to well developed aerobic, anoxic, anaerobic microbial conditions.