STEADY-STATE AND TRANSIENT-BEHAVIOR IN MICROBIAL METHANIFICATION .2. MATHEMATICAL-MODELING AND VERIFICATION

Since in the Upflow Anaerobic Sludge Bed (UASB) system the biocatalyst is flocculated, it was found that a model additionally incorporating this facet of the reactor set-up could explain the steady-state data very well. By using the parameters generated from steady-state data and data from butyric acid step change, a very good agreement between predicted and observed data was found. International Mathematical and Statistical Libraries (IMSL) and Upjohn's NONLIN library combined with various root-finding and integrating subroutines were used for parameter estimation. The model thus described was used to predict the response of the UASB system when acetic acid and propionic acid influent concentrations were stepped-up/down. The agreement between the predicted and observed data was found to be excellent in each case during the step-up schedule. During the step-down the data seemed to indicate that the UASB system, like any other chemostat, responded faster than predicted.