Modeling of fluidized bed bioreactors for treating wastewaters: evaluation of mass transfer and flow condition hypotheses

FUENTES MORA, MAUREN; AGUIRRE, PÍO; SCENNA, NICOLÁS

Buenos Aires, Argentina

Congreso; XII Interamerican Congress of Chemical Engineering and V Argentinean Congress of Chemical Engineering; 2006

Asociación Argentina de Ingenieros Químicos (AAIQ)

The main purpose of this paper is modeling mass transfer phenomena and hydrodynamics in anaerobic fluidized bed reactors (AFBRs) for treating wastewaters. The Anaerobic Digestion Model No. 1 (ADM1) is selected to describe the substrate degradation scheme and is applied to a biofilm system. Simulated responses from four versions of the AFBR model are compared to analyze the adequacy of some hypotheses related to: (a) the hydrodynamic behavior of anaerobic bioreactors, which is sometimes assumed as two-phase solid-liquid systems, because of the minimal amount of generated gas; and (b) a totally developed flow condition, since fluidized beds are considered “high rate” systems. The results from a heterogeneous model of the three-phase (gas-solid-liquid) and one-dimensional dynamic system are considered as a reference point. All model versions simultaneously compute the phases and components dynamics, including the effect of biofilm growth in the fluidization characteristics and interaction among them in biological transients. For the evaluated study case, predictions from model version based on hypothesis (a), regarding biofilm concentration and thus, biogas production and chemical oxygen demand (COD) removal efficiency, differ in 5% with the three-phase model ones. Model simplification considering totally developed (complete mixture) flow is acceptable for describing high rate fluidized bed reactor performance, and errors less than 2% are obtained in the predicted values of the main macroscopic variables.