Steady state behaviour of three phase air lift bioreactors - an integratedmodel and experimental verification

Beneckea natriegens growing bath in suspension and immobilised on diatomace ous earth (silica) support particles, in a 3 dm three phase air lift biorea ctor (TPALB), was employed to demonstrate the relationship between substrat e loading rate and immobilised biomass loading at steady state. Sterile con ditions were maintained during the experiments, while the hydraulic conditi ons and the inlet flowrate remained constant. The experiment ran for 12 day s, whilst the inlet substrate (n-propanol) concentration was varied both up wards and downwards between 250 and 750 mg dm(-3). The bulk liquid substrat e concentration and the immobilised biomass loading were found to vary betw een 6-120 mg dm(-3) and 71-159 mg (dry biomass) g(-1) (silica), respectivel y. The experimental results demonstrated that there is a positive relations hip between substrate loading and immobilised biomass loading. A mathematic al model is proposed to calculate biofilm thickness and bulk liquid substra te concentration (for steady state) using the inlet flowrate and the inlet substrate concentration as input parameters. The model was able to predict both biofilm thickness and immobilised biomass loading for the lower substr ate loading rates applied. (C) 1999 Society of Chemical Industry.