Submerged hollow-fiber membranes

FIGURE 8.37 Submerged hollow fiber membrane module, (a) Flat sheet and (b) hollow fiber. (From Figures 19a and 21b in Cui, Z.F., Chang, S., and Fane, A.G., J. Membr. Sci., 221, 1, 2003. With permission.)... 

Chang S and Fane AG, Filtration of biomass with lab-scale submerged hollow fiber membrane module Effect of operational conditions and module configuration, J. Chem. Technol. Biotechnol. 2002 77 1030-2212. 

Genkin G, Waite TD, Fane AG, and Chang S, The effect of axial vibrations on the filtration performance of submerged hollow fiber membranes International Congress on Membranes and Membrane Processes, ICCIM, Korea, Seoul, 2005. 

Figure 10.34b shows a vibrating submerged hollow fiber membrane system for filtration applications [81]. In this system, the submerged membrane is vibrated by a mechanical... 

FIGURE 10.36 Schematics of different vibration strategies for submerged hollow fiber membranes, (a) Vertical vibration, (b) transverse vibration, and (c) liquid oscillation. 

P.R. Berube and E. Lei, The effect of hydrodynamic conditions and system configurations on the permeate flux in a submerged hollow fiber membrane system, J. Membr. Sci., 271 (2006) 29-37. 

Chang, S., Fane, A. G., and Vigneswaran, S. (2002). Modeling and optimizing submerged hollow fiber membrane modules. AIChE J. 48(10), 2203-2212. 

The ultrafiltration unit, containing submerged polyvinylidenefluoride (PVDF) hollow-fiber membranes (ZeeWeed by Zenon), is designed to treat 1600 m3/h of wastewater with a COD/h of445 kg and the suspended matter of the treated water is <1 mg/L [21]. 

Figure 16.8 Cross-sections of a (a) pressurized MF or UF hollow fiber membrane module and an (b) submerged hollow fiber MF membrane cartridge.

Fig. 9 Two operating configurations for hollow fiber membranes (A) submerged (or immersed) and (B) sidestream (or cross-flow)...

FIGURE 10.43 Effect of gas velocity on final flux in filtration with submerged membranes. (Reprinted from J. Membr. ScL, 184, Chang, S. and Fane, A.G., The effect of fiber diameter on filtration and flux distribution—Relevance to submerged hollow fiber modules, 221-231, Copyright 2001, with permission from Elsevier.)... 

The early references to submerged membranes came from Japan. Ohkubo et al. (1988) obtained a patent describing hollow fibers in a vertical bundle in a vessel with air scour to vibrate the fibers to remove the cake. The first reported use of submerged hollow fibers in a wastewater membrane bioreactor (MBR) was by Yamamoto et al. (1989), who used fibers in a bundle and air bubbles for aeration, mixing, and induced liquid flow. Permeate was removed by suction. At that time the concept was more of a curiosity, but within a decade the submerged membrane has become the dominant approach for low-pressure membrane processing in the water and wastewater industry. 

The use of bubbly flow has been reviewed by Cui et al. (2003). Figure 10.11 depicts the role of bubbles in the enhancement of filtration by submerged hollow fibers. For submerged flat sheets similar mechanisms apply except for the lack of induced membrane movement. 

In MBRs bubbling also has a role in mixing the reactor contents, presumably through the induced liquid circulation [Eq. (10.11)]. There is some evidence from tracer studies that mixing induced by bubbles may be a httle more effective with submerged hollow fibers than flat-sheet membranes because the latter act as baffles in the vessel (Wang et al., 2008). 

Submerged membranes are operated with the feed in a vessel at atmospheric pressure. To obtain a TMP, the permeate side has to be below atmospheric pressure, and this is achieved by suction provided by permeate pumping. The pressure on the permeate side will be determined by the TMP defined by Eq. (10.3) as well as a presstrre drop due to permeatc-side (lumen) flow, which may be significant for hollow fibers. This situation has been analyzed for vertical submerged hollow fibers closed at the bottom and with suction at the top. The situation is depicted in Figure 10.18a for a clean water feed, and the axial flux distribution can be estimated from (Chang et al., 2000)... 

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