Kinetics of growth and substrate uptake in a biological film system.

The rates of growth and substrate uptake in a biological film continuous-flow reactor were studied. The experiments were performed with high fluid velocities to bring the reactor operation to the reaction-controlled regime, thus avoiding external diffusional resistances. The glucose uptake experiments were performed with small film thicknesses so that full substrate penetration within the entire film thickness could be obtained. In this way, the catalyst effectiveness factor was 1.0 and the observed rate was the true, or intrinsic, rate. The results of the experiments indicate that both the intrinsic rate of substrate uptake and the rate of film growth are independent of the substrate concentration remaining in the reactor (zero-order reactions). However, the value of the initial substrate concentration when the film is in the early stages of growth defines the magnitude of both the rate of uptake and growth. This effect of the initial substrate concentration follows a saturation-function pattern.