Mathematical modelling for supporting scale-up of an anaerobic wastewater treatment in a fluidized bed reactor

Abstract

The paper deals with a mathematical model for anaerobic treatment of waste water from sugar industry which has been developed for supporting the scale-up of a fluidized bed reactor. The dynamic model is based on material balance equations for substrates and products in gas and liquid phase. The effects taken into account are the biological degradation steps including chemical equilibria and mass transport between gas and liquid phase as well as convection and dispersion. Axial gradients of pH-values are calculated from a charge balance. Simulation results show reasonable agreement with measured gradients of substrates and pH in a 10 m3 fluidized bed reactor. For a new 500 m3 fluidized bed reactor simulations are performed to study the effects of increased hydrostatic pressure and increased ratio of feed to recirculation rate on the pH-values at the bottom of the reactor. The results indicate that for high COD-loading rates stationary pH-gradients may have significant influence upon the outcome of the process.