Variation of superficial velocity of a submerged module (YEF) by module size and aerator types

The superficial velocity of a submerged module (YEF) was investigated to design better air distribution system. Air from the aerator tends to channel more to center part as the module becomes bigger. A 3-way aerator showed more uniform distribution of air bubbles among the fibers. Therefore, the 3-way aerator was selected as an optimized aerator for modules with 500 and 1000 mm diameters. In tissue suspension filtration, the critical fluxes of 500A and 1000A. Submerged modules were 30 LMH (L/m2/h) and 15 LMH, respectively. In kaolin suspension tests, different flux declining trend of the modules was observed. The flux decreased with the increase of kaolin concentration and with the decrease of air flow rate. An optimum air flow rate to maintain a critical flux existed. Cake resistance decreased as the air flow increased, but did not decrease further over a certain air flow rate.

The superficial water velocity of larger submerged module was getting lower than that of smaller modules, because the air from the aerator tends to channel more into the center section as the module becomes larger. A 3-way type aerator showed the most uniformly distributed air bubbles among the fibers. In tissue suspension filtration, the critical fluxes of 500A and 1000A modules were 30 and 15 LMH, respectively. In the kaolin suspension test, the flux decreased with an increase of the kaolin concentration and with the decrease in the air flow rate. An [1] Simon Judd, The MBR Book, Elsevier Publisher, 2006. [2] Y. Shimazu, K. Uryu, Y.-L. Okuno and A. Watanabe, Cross flow microfiltration of activated sludge using submerged membrane with air bubbling, J. Ferment. Bioeng., 81 (1) (1996) 55–60. [3] P. Le-Clech, B. Jefferson and S.J. Judd, A comparison of submersed and sidestream tubular membrane bioreactor configurations, Desalination, 173 (2005) 113–122. [4] Z.F. Cui, S. Chang and A.G. Fane, The use of gas bubbling to enhance membrane process, J. Membr., Sci., 221 (2003) 1–35. [5] A. Yeo and A.G. Fane, Performance of individual fibers in a submerged hollow fiber bundle, Water Sci. Technol., 51 (2005) 165–172. [6] S. Chang and A.G. Fane, Characteristics of microfiltration of suspensions with inter-fibre two-phase flow, J. Chem. Technol. Biotechnol., 75 (2000) 533–540. [7] O.S. Kwon, Hydraulic characteristics of YEF (Yonsei End Free) hollow fiber membrane module for scale-up, Master, dissertation, Dept. Environ. Engin., Yonsei Univ. (2003). [8] M.Y. Chisti, Airlift Bioreactors, Elsevier Publisher, 1989. [9] T. Ueda, K. Hata, Y. Kikuoka and O. Seino, Effects of aeration on suction pressure in a submerged membrane bioreactor, Water Res., 31 (3) (1997) 489–494. [10] R. Liu, X. Huang, C. Wang, L. Chen and Y. Qian, Study on hydraulic characteristics in a submerged membrane bioreactor process, Process Biochem., 36 (2000) 249–254.