1989 Volume 25 Pages 209-220
For rational design and operation of biofilm reactor for treatment of water and wastewater it is necessary to clarify the mechanism of biofilm formation and detachment and to estimate biomass hold-up retained within the reactor. In this study a relationship between the adhesive strength of cells, the biofilm detachment rate and the content of extracellular biopolymer was quantified to investigate what factors govern the phenomenon of biofilm detachment. Experimental biofilm which consisted of denitrifying microorganisms were established on inner surface of tubes. The critical value as Bingham fluid for biofilm which corresponds to adhesive strength between cells was much higher than fluid shear stress acting on biofilm surface. Therefore not only extrinsic factors like fluid shear stress but also intrinsic factors of biofilm physiological conditions may take a important role in biofilm mechanical structure and detachment. The high correlation between biofilm loss rate and biofilm mass per unit area was observed. With an increase in biofilm mass per unit area, the content of extracellular biopolymer decreased, whereas gas content within biofilm increased. The magnitude of biofilm detachment seemed to be attributable to the content of extracellular biopolymer and gas production.
