Mathematical model for the biodegradation of VOCs in trickle bed biofilters

Abstract

The objective of this work is to develop a fundamental mathematical model that describes the biodegradation of volatile organic compounds (VOCs) in gas phase trickle-bed biofilters, and to estimate the unknown model parameters. The mathematical model considers a three-phase system (biofilm, water, and gas phase), non-uniform bacterial population, and one limiting substrate. Two pilot-scale trickle-bed biofilters were operated to remove the VOC diethyl ether from a waste gas stream. Experimental results from this system were used to estimate the unknown parameters of the steady-state model: the maximum rate of substrate utilization μmXf/Y, the Monod constant, Ks, and the ether biofilm/water diffusivity ratio, rd. While the value of μmXf/Y was uniquely determined, the values of Ks and rd were highly correlated. High values of the Monod constant and the ether diffusivity in the biofilm gave similar predictions to those corresponding to low values of both parameters. Batch studies were used to estimate the value of Ks without mass transfer limitations showing that Ks < 1 mg/L=2.6 mg COD/L. Using this information and biofilter operating data the true values of Ks and rd were determined.