Biofilm loss in anaerobic immobilized fixed bed reactor system

An anaerobic immobilized fixed bed bioreactor system was studied for treatment of herbal-based pharmaceutical wastewater. The biofilm loss rate (R(S)), shear stress (sigma), biofilm thickness (Lf) and biomass concentration (X,) were investigated for various flow rates applied to the bioreactor during the experimental studies. Some relationships applicable to a fixed bed reactor were obtained between biofilm loss rate, shear stress, biofilm thickness and specific flow rate (Q) with good accuracy. It was evident that shear stress and biofilm loss rate increased with increase in biofilm thickness. A similar trend was also observed with an increase in flow velocity. It was found that shear stress plays a major role in the biofilm detachment mechanism. The biofilm thickness determined in the present investigation was in the range of 0.5 mm to 5.5 mm, and the biofilm loss rate was estimated in the range of 1.7 x 10(-4) to 7.8 x 10(-4) kg COD m(-2) d(-1) at flow rate ranging between 5.0 and 50 1 d(-1).