Measurement of the Activity of a Biofilm: Effects of Surface Loading and Detachment on a Three-Phase, Liquid-Fluidized-Bed Reactor

A method to measure the fraction of biofilm bacteria active in respiration was developed and applied to a three-phase fluidized-bed biofilm reactor. The substrate flux (J) and the biofilm detachment coefficient (b_s) were controlled independently. The experimental results showed that the amount of biofilm per unit of carrier surface area (X_fL_f) was controlled by J and b_s. However, the biofilm's active fraction was proportional to J, but independent of b_s for these experiments with relatively large b_s values. When J was increased, the biofilm had less inactive biomass, because the substrate concentration was higher and allowed the cells to maintain a higher growth rate. Accompanying the increased activity were an increase in the observed biomass yield and a decrease in the oxygen consumption. These results provide a tool to control bioparticle fluidization, oxygen consumption, and sludge production.