Analysis of Trickle Bed and Packed Bubble Column Bioreactors for Combined Carbon Oxidation and Nitrification

Abstract

Biological removal of nitrogen and carbon by combined nitrification-oxidation in gas-liquid trickle-bed reactors (TBRs) and packed bubble columns (PBCs) was analyzed theoretically using a transient two-dimensional model. The model describes TBR and PBC performances at steady state as well as their transient response to a pulse or step increase in inlet methanol and NH4+-nitrogen concentrations. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time-domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the piston-dispersion-exchange model was used to interpret the residence time distribution curves obtained. Gas-liquid mass transfer parameters were determined by a stationary method based on the least-squares fit of the calculated concentration profiles in gas phase to the experimental values. Analysis of steady-state performances showed that under like operating conditions, the TBR outperforms the PBC in terms of conversions. A pulse change in the inlet methanol or NH4+-nitrogen concentration causes a negligible transient change in the outlet methanol concentration and a negligible or high transient change in the outlet NH4+-nitrogen concentration. A step change in the inlet methanol concentration causes the negligible transient change in the methanol outlet concentration and a relatively important transient change in the NH4+-nitrogen outlet concentration. A step increase in the NH4+-nitrogen inlet concentration induces a drastic transient change in the NH4+-nitrogen outlet concentration but a negligible transient change in the methanol outlet concentration

Modeling the effects of biomass accumulation on the performance of a biotrickling filter packed with PUF support for the alkaline biotreatment of dimethyl disulfide vapors in air

“…Further assessment at this scale includes the evaluation of the residence time distribution technique (RTD), which has been used for characterizing the hydrodynamics in biotrickling filters (Iliuta et al 2002;Trejo-Aguilar et al 2005, Sharvelle et al 2008a. It is often considered that the liquid movement through a porous bed occurs by an ideal plug flow pattern.…”

“…To date only few models include liquid dispersion to simulate gas treatment performance in biofilters and biotrickling filters (Zarook et al 1998;Iliuta et al 2002;Sharvelle et al 2008b). Some other include interesting analyses through biomass growth functions to predict its influence on the biofiltration process (Alonso et al 1996;Alonso et al 1998;Iliuta et al 2002).…”

“…Some other include interesting analyses through biomass growth functions to predict its influence on the biofiltration process (Alonso et al 1996;Alonso et al 1998;Iliuta et al 2002). However these models were focused on packing particles with relatively simple geometries.…”

Experimental analysis and evaluation of the mass transfer process in a trickle-bed reactor

“…The theoretical model described here is onedimensional and based upon the concentration of the gas tracer in the gas, liquid, and solid phases during cocurrent operation (Silva et al, 2000a;Burghardt et al, 1990;Ramachandran and Smith, 1979;Iliuta et al, 2002). The model adopted for the gas tracer within these phases is constrained by the following simplifications: (i) the system is isothermal; (ii) the gas phase is modeled as a plug flow; (iii) the liquid phase is modeled taking axial dispersion into account; (iv) the system operates with partial wetting of the bed; (v) there is intraparticle diffusion in the pores of the spherical catalytic particle; (vi) rapid adsorption equilibrium is achieved in the system; (vii) the system operates with a small concentration of the tracer in order to minimize disturbances to reactor conditions.…”

Application of Laplace Transform for a Gas-Liquid-Solid Trickle Bed Reactor by Using the Tracer Technique

“…Those models are based on many assumptions and they are forced to using simplifications to solve the complex equation systems. Mathematical models of TBRs may involve the mechanisms of forced convection, axial dispersion, interphase heat and mass transfers, intraparticle diffusion, adsorption, and chemical reaction [4,5].…”