EVALUATION OF FORMALDEHYDE REMOVAL FROM CONTAMINATED AIR BY USING A BIOTRICKLING FILTER REACTOR IN A CONTINUOUS CONDITION

Introduction: Formaldehyde is a toxic, mutagen and teratogen chemical, and it is suspected to be carcinogenic to humans. As a result, it can be classified as a noxious air pollutant which must be removed from any formaldehyde-contaminated air stream before releasing to the atmosphere. Biological methods, particularly biotrickling filtration, have recently attracted a great deal of attention due to low operating cost and high removal efficiency. Materials and Methods: In this study, the biotrickling filtration of air stream contaminated by formaldehyde was investigated in a continuous system. The main objective of this study was to investigate formaldehyde biotrickling processes in continuous mode, culminating in the development of a mathematical relation to correlate volumetric mass transfer coefficient versus the Reynolds number of gas flow. During these experiments, formaldehyde removal efficiencies of 97, 97.5 and 96.5% were achieved for the gas flow rates of 90, 291 and 1512 l/h, respectively. Biotrickling filter reactor (BTFR) was employed for this continuous experiment. Results: The results obtained in this study show that the mass transfer from gas phase to the gas-wet biomass interphase is the controlling step, and the reaction rate is not an important factor in this case for a wide range of gas flow rates and gas velocities. Conclusions: The analyses demonstrate that external mass transfer is the controlling step compared to diffusion through liquid phase and bio-reactions. The results also show that using smaller but longer beds resulting in higher velocities enhances the mass transfer rate and hence the removal efficiency.