Modeling variations of medium porosity in rotating drum biofilter

Area of Science:

• Environmental Engineering
• Biotechnology
• Chemical Engineering

Background:

• Rotating drum biofilters (RDBs) with polyurethane sponge media demonstrate high efficiency for volatile organic compound (VOC) removal.
• Biomass accumulation in RDBs dynamically alters filter bed porosity, complicating performance prediction and control.

Purpose of the Study:

• To investigate the temporal and spatial changes in porosity within a multi-layer RDB bed.
• To develop a diffusion-reaction model accounting for biofilm growth and decay at the pore scale.
• To assess the relationship between porosity variations and biofilter performance.

Main Methods:

• A diffusion-reaction model was developed to simulate porosity changes in RDBs, considering biofilm dynamics.
• The model incorporated pore-scale biofilm growth and decay, assuming porosity is a function of biofilm thickness.
• Numerical methods using MATLAB were employed to solve the model, with toluene as the model VOC.

Main Results:

• Biofilter porosity decreased over time, with increased toluene loading, and decreased gas empty bed contact time (EBCT).
• Outer medium layers exhibited lower porosity than inner layers due to biomass accumulation.
• Model-calculated porosities and toluene removal efficiencies showed good correlation with experimental data.

Conclusions:

• Porosity variation in RDBs is influenced by operational parameters like loading and EBCT.
• Porosity changes dynamically and spatially within the biofilter bed.
• Porosity variation can serve as a predictive indicator for biofilter performance in VOC removal applications.