Hydrodynamics and mass transfer inthree-phase airlift reactors for activated Carbon and sludge filtration

Document Type : Research Paper


1 Department of Chemical Engineering, University of Guilan

2 Msc, Department of Chemical Engineering, Guilan University, Rasht, Iran


A bioreactor refers to any manufactured or engineered device that supports a biologically active environment. These kinds of reactors are designed to treat wastewater treatment. Volumetric mass transfer coefficient and the effect of superficial gas velocity, as the most important operational factor on hydrodynamics, in three-phase airlift reactors are investigated in this study. The experiments for the external airlift reactor were carried out at a 0.14 downcomer to riser cross-sectional area ratio, and for the internal reactor at 0.36 and 1. Air and water were used as the gas and liquid phases, respectively, as well as activated carbon/sludge particles as the solid phase. Increasing the superficial gas velocity resulted in greater liquid circulation velocity, gas hold-up, and volumetric mass transfer coefficient; increasing the suspended activated carbon particles resulted in a decreased concentration of activated sludge, downcomer to riser cross sectional area ratio, liquid velocity, gas hold-up and volumetric mass transfer coefficient. The maximum gas hold-up was 0.178 which was attained in the external airlift reactor with a 1 Wt. % of activated sludge at a gas superficial velocity of 0.25 (m/s). The maximum volumetric mass transfer coefficient was 0.0485 (l/s) that was observed in the external airlift reactor containing activated carbon with a 0.00032 solid hold-up. A switch was observed in the activated sludge airlift reactor flow regime at gas velocities higher than 0.15 (m/s) and 0.18 (m/s) in the activated carbon airlift reactors.


Main Subjects

[1] Bentifraouine, C., Xuereb, C., Riba, J. P. (1997). An experimental study of the hydrodynamic characteristics of external loop airlift contactors. Journal of chemical technology and biotechnology, 69(3), 345-349.
[2] García‐Calvo, E., Letón, P. (1996). Prediction of gas hold‐up and liquid velocity in airlift reactors using two‐phase flow friction coefficients. Journal of chemical technology and biotechnology, 67(4), 388-396.
[3] Bakker, W. A. M., Van Can, H. J. L., Tramper, J., De Gooijer, C. D. (1993). Hydrodynamics and mixing in a multiple air‐lift loop reactor. Biotechnology and bioengineering, 42(8), 994-1001.
[4] Muroyama, K., Mitani, Y., Yasunishi, A. (1985). Hydrodynamic characteristics and gas-liquid mass transfer in a draft tube slurry reactor. Chemical engineering communications, 34(1-6), 87-98.
[5] Merchuk, J. C., Gluz, M. (2002). Bioreactors, Air-lift Reactors. Encyclopedia of Bioprocess Technology, Wiley Online Library.
[6] Jin, B., Leeuwen, J. H. V., Doelle, H. W., Yu, Q. (1999). The influence of geometry on hydrodynamic and mass transfer characteristics in an external airlift reactor for the cultivation of filamentous fungi. World journal of microbiology and biotechnology, 15(1), 73-79.
[7] Nikakhtari, H., Hill, G. A. (2005). Hydrodynamic and oxygen mass transfer in an external loop airlift bioreactor with a packed bed. Biochemical engineering journal, 27(2), 138-145.
[8] Jin, B., Yin, P., Lant, P. (2006). Hydrodynamics and mass transfer coefficient in three-phase air-lift reactors containing activated sludge. Chemical engineering and processing: Process intensification, 45(7), 608-617.
[9] Freitas, C., Teixeira, J. A. (2001). Oxygen mass transfer in a high solids loading three-phase internal-loop airlift reactor. Chemical engineering journal, 84(1), 57-61.
[10] Yang, F., Bick, A., Shandalov, S., Brenner, A., Oron, G. (2009). Yield stress and rheological characteristics of activated sludge in an airlift membrane bioreactor. Journal of membrane science, 334(1), 83-90.
[11] Al Taweel, A. M., Idhbeaa, A. O., Ghanem, A. (2013). Effect of electrolytes on interphase mass transfer in microbubble-sparged airlift reactors. Chemical engineering science, 100, 474-485.
[12] Kilonzo, P. M., Margaritis, A., Bergougnou, M. A., Yu, J., Ye, Q. (2007). Effects of geometrical design on hydrodynamic and mass transfer characteristics of a rectangular-column airlift bioreactor. Biochemical engineering journal, 34(3), 279-288.
[13] Krichnavaruk, S., Pavasant, P. (2002). Analysis of gas–liquid mass transfer in an airlift contactor with perforated plates. Chemical engineering journal, 89(1), 203-211.
[14] Lu, W. J., Hwang, S. J., Chang, C. M. (1995). Liquid velocity and gas holdup in three-phase internal loop airlift reactors with low-density particles. Chemical engineering science, 50(8), 1301-1310.
[15] Kadic, E. (2010). Survey of gas-liquid mass transfer in bioreactors.
[16] Clarke, K. G., Correia, L. D. C. (2008). Oxygen transfer in hydrocarbon–aqueous dispersions and its applicability to alkane bioprocesses: A review. Biochemical engineering journal, 39(3), 405-429.
[17] Benyahia, F., Jones, L. (1997). Scale effects on hydrodynamic and mass transfer characteristics of external loop airlift reactors. Journal of chemical technology and biotechnology, 69(3), 301-308.
[18] Bai, F., Wang, L., Huang, H., Xu, J., Caesar, J., Ridgway, D., Moo-Young, M. (2001). Oxygen mass-transfer performance of low viscosity gas-liquid-solid system in a split-cylinder airlift bioreactor. Biotechnology letters, 23(14), 1109-1113.