Simulation Of Volatile Organic Compounds Removal In Bio-trickling Filters

Bio-trickling Filters (BTFs) is an effectively control means for volatile organic compounds (VOCs), which utilizes microbe attached on the packing media to capture volatile organic compounds (VOCs) and biodegrade them. It has advantages in some aspects such as low cost, handy operation costs and no recontamination. Additional, the technology can overcome the disadvantages including the short of gas flow, the uneven distribution of organic loading and nutrients in conventional biofilters, and to an extent released the biomass excess accumulation or clogging in the filter bed. It would be important theory and practical significance in the research and application of bioreactors for VOCs removal to simulate the complex processes, such as the BTFs for VOC removal at different operating conditions, the dynamic kinetics of biomass growth, the spatial and temporal changes in biomass distribution, and the biomass accumulation rate.A mathematical model was developed on the basis of mass transport and mass balance equations in a BTF, the two-film theory, and the Monod kinetics. This model took account of mass transfer and biodegradation of VOC in the gas-water-biofilm three-phase system in the biofilter, and could simulate variations of VOC removal efficiency with a changing specific surface area and porosity of the media due to the increasing of biofilm thickness in the biofilter. This model was further simplified by neglecting the water phase due to the small mass transfer resistence. The equations for the biofilm phase, gas phase, and biofilm accumulation in this model were solved using collocation method, analytic method, and the Runge-Kutta method separately. A computer program was written down as MATLAB to solve this model.The results of numerical solutions show that toluene removal efficiency increased with the gas resistence time increased and decreased with the organic loading increased. The porosity of the packing in the inlet decreased with the gas resistence time increased and decreased with the organic loading increased. The biomass accumulation rate in the bio-trickling filter increased with the gas resistence time increased and increased with the organic loading increased. The concentration profile of toluene in bio-trickling filter revealed that the packing layer which is the closest to inlet played the most important role in toluene biodegradation.The dynamic removal efficiencies from this model correlated reasonably well with experimental results for toluene removal in a BTF. It provides the basis for the spreading and application of biofiltration on the waste gas treatment.