GAS TREATMENT IN TRICKLE-BED BIOFILTERS - BIOMASS, HOW MUCH IS ENOUGH

The objective of this article is to define and validate a mathematical model that describes the physical and biological processes occurring in a trickle-bed air biofilter for waste gas treatment. This model con siders a two-phase system, quasi-steady-state processes, uniform bacte rial population, and one limiting substrate. The variation of the spec ific surface area with bacterial growth is included in the model, and its effect on the biofilter performance is analyzed. This analysis lea ds to the conclusion that excessive accumulation of biomass in the rea ctor has a negative effect on contaminant removal efficiency. To solve this problem, excess biomass is removed via full media fluidization a nd backwashing of the biofilter. The backwashing technique is also inc orporated in the model as a process variable. Experimental data from t he biodegradation of toluene in a pilot system with four packed-bed re actors are used to validate the model. Once the model is calibrated wi th the estimation of the unknown parameters of the system, it is used to simulate the biofilter performance for different operating conditio ns. Model predictions are found to be in agreement with experimental d ata. (C) 1997 John Wiley & Sons, Inc.