Aspects on Methanogenic Biofilm Reactor Modeling

−− A previously developed deterministic steady state module for modeling methanogenic biofilm reactors has been revised to enlarge the model application range and to deal with system dynamics. Two models for the hydrolysis of non-active biomass representing extreme alternatives: without biomass hydrolysis (model A) and with complete and instantaneous hydrolysis of non-active suspended and attached biomass (model B) were investigated. Both models resulted to be suitable for simulating highly anaerobic loaded systems. However, only model B showed good agreement between experimental and calculated values at low organic loading rates. The values of the specific biofilm detachment rate and the specific microbial death rate of the original model were re-estimated for model B based on a set of step-type disturbances on the organic loading rates. At loading rates ranging between 2 to 4 g COD per day per liter of expanded bed applied to a lab-scale fluidized bed reactor, the parameter estimates were 0.0269 Lgd and 0.061 d for the specific biofilm detachment rate and the specific death rate, respectively, with a 95% chi-square confidence level. Keywords−− Anaerobic digestion, biofilm reactor, process dynamics, biomass hydrolysis.