ANAEROBIC BIOFILM REACTOR MODELING FOCUSED ON HYDRODYNAMICS

Abstract

This work deals with an experimental and theoretical investigation of anaerobic biofilm reactors for treating wastewaters. Bioreactors are modeled as dynamic (gas-solid–liquid) three-phase systems. The anaerobic digestion model proposed by Angelidaki et al. (1999) was selected to describe the substrate degradation scheme and was applied to a biofilm system. The experimental setup consists of two mesophilic (36°±1°C) lab-scale anaerobic fluidized bed reactors (AFBRs) with sand as inert support for biofilm development. The experimental protocol is based on step-type disturbances applied on the inlet substrate concentration (glucose and acetate-based feeding) and on the feed flow rate considering the criterion of maximum efficiency. The predicted and measured responses of biological and hydrodynamic variables are investigated. Experimental data were used to estimate empirical values of biofilm detachment coefficients. Under the evaluated operating conditions, the proposed model for biofilm detachment rate, assumed as a first-order function of the energy dissipation parameter, is appropriate to represent the interaction between biofilm systems and fluidization characteristics in non-highly disturbed flow conditions. Model validation was carried out using the experimental data reported by Mussati et al. (2006). The results do not differ from those above. This seems to indicate that the proposed AFBR model is able to reproduce the main biological and hydrodynamic successes in the bioreactor.

Keywords:

• Biofilm detachment
• Fluidized bed bioreactor
• Process dynamics
• Hydrodynamics

Acknowledgments

The authors acknowledge financial support from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional para la Promoción de la Ciencia y la Tecnología (ANPCyT), and Universidad Nacional del Litoral of Argentina.

Notes

See Nomenclature for notation.

^a Suggested by Perry and Chilton (1973) for smooth rigid spheres.

^b Authors suggested the equation reported by Shieh and Chen (1984) to calculate the expansion coefficient n.