Modeling and simulation of a biofilter

Treatment of air streams contaminated with volatile organic compounds in a biofilter under transient and steady-state conditions of operation is descr ibed with a mathematical model. The model incorporates convection and dispe rsion in the gas phase, partial coverage of the solid support, interphase m ass transfer between the gas and the aqueous biofilm with an equilibrium pa rtition at the interface followed by diffusion, direct adsorption to the ex posed uncovered solid adsorbent media, transfer between the biofilm and the solid support, and biological reactions in both the biofilm and the adsorb ent. The model equations were solved numerically by the method of orthogona l collocation using a MATLAB computer code. The effects of pollutant disper sion in the gas phase, specific surface area available for mass transfer, t hickness of the biofilm, and adsorptive capacity of the solid support on th e biofilter performance were investigated in detail. The steady-state remov al efficiency appears to be nearly independent of gas-phase dispersion of t he pollutant in the normal industrial range of operations. Results also ind icate that the biofilter performance is a strong function of specific surfa ce area for mass transfer and biofilm thickness. Simulation results further suggest that higher adsorptive support media are capable of handling load fluctuations irrespective of the rate of reaction in the adsorbed phase.