Dynamic Mathematical Model for the Biodegradation of VOCs in a Biofilter:  Biomass Accumulation Study

Abstract

Although biofiltration is a firmly established technology for the control of emissions of volatile organic compound (VOCs), more fundamental research is still needed. This work uses a mathematical model describing the dynamic physical and biological processes occurring in a packed trickle-bed air biofilter to analyze the relationship between biofilter performance, biomass accumulation in the reactor, and mathematical description of the packed bed porous media. In this study a biofilter packed with pelletized support media was used to treat toluene achieving removal efficiencies over 99% and 97% for 4.1 and 6.2 kg COD/m3 day toluene loading, respectively. Experimental results showed that as biomass accumulates in the reactor, the available area for the contaminant to diffuse into the biofilm decreases causing a drop in removal efficiency. This effect is specially important for biofilters where there is a high degree of biomass accumulation that significantly affects biofilter performance. In response to these observations, a new approach for the calculation of the biofilm specific surface area of the reactor as a function of biomass growth was developed. Three models of the reactor porous medium were analyzed. The medium was represented as a bed of equivalent spheres in the first model, as an equivalent set of parallel pipes in the second model, and as an equivalent set of flat parallel plates in the third model. The first two models, spheres and pipes, were proven superior in their ability to explain the system performance. The effect of contaminant solubility on biofilter performance was also analyzed.

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

“…From this point on specific area diminishes as consequence of further biofilm accumulation. In this respect, a mathematical representation of a biofilter with specific area dependence on biofilm growth was previously reported (Alonso et al 1998). These authors considered spherical geometry for packing particles and model predictions respecting pollutant removal were in well agreement with experimental data, however the estimated specific area was invariably decreasing since theoretical biofilm development began.…”

“…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.…”

A Fundamental Study of Biofiltration Processes for VOC Removal From Waste Gas Streams

“…More detailed descriptions and discussions of this model can be found in Alonso (1999) and Alonso et al (1997aAlonso et al ( , 1998Alonso et al ( , and 2000.…”

Biofiltration of odorous fume emitted from recycled nylon melting operations

“…In a typical biofilter process configuration, VOC-contaminated gas is humidified and passed through a packed bed containing solid media that support a biologically active layer (Devinny et al, 1999). Biofiltration of gases containing VOCs has proven to be an effective and economical technology (Alonso et al, 1998;Deshusses et al, 1999;Mohseni et al, 1999Mohseni et al, , 2000Mudliar et al, 2010). Under optimum conditions, biodegradable contaminants are rapidly converted to carbon dioxide and water without the accumulation of intermediates or dead-end metabolites.…”