Specific activity of nitrifying biofilm in water nitrification process

The effect of the accumulation of fixed biomass on the specific activity of nitrifying biofilm was studied in a continuous flow reactor. The specific activity of nitrifying biofilm was described by the specific removal rate of ammonium-N (qobs). The observed relationship between qobs and the film thickness was apparent to an inverse V-shaped curve. The maximum specific activity of biofilm was attained at a film thickness in the range 15–25 μm, at which a steady state was established in the liquid phase for different influent ammonium-N concentrations (S0). Beyond such a range, the specific activity began to decline significantly with the additional accumulation of biofilm. It was demonstrated from both experimental and theoretical approaches that reduction in the specific activity of biofilm was closely related to the ratio of active biomass to the accumulation of inactive materials within the biofilm.