Tehran University of Medical Sciences Journal of Air Pollution and Health 2476-3071 1 2 2016 05 29 69 76 EN Amirreza Talaiekhozani Department of Civil and Environmental Engineering, Jami Institute of Technology, Isfahan Mohammad Talaie Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran Mohamad Fulazzaky Institute of Environmental and Water Resources Management, Water Research Alliance, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bharu, Malaysia 2016 05 29 2016 05 29 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. https://japh.tums.ac.ir/index.php/japh/article/view/37 https://japh.tums.ac.ir/index.php/japh/article/download/37/10