Immersed membranes

Figure 14.3 Schematic illustration of immersed membrane bioreactor configurations.

In this case the fluid phase is aerated (in the case of aerobic bioreactor) that maintains the turbulent hydrodynamic conditions on the one hand, and prevents the forming of the cake layer on the immersed membrane module, on the other hand. The reactor description is also well known [67], and is not discussed here. 

Choksuchart, P., Heran, M. and Grasmick, A. (2002) Ultrafiltration enhanced by coagulation in an immersed membrane system. Desalination, 145, 265—272. 

Cote, P., Buisson, H. and Praderie, M. (1998) Immersed membranes activated sludge process applied to the treatment of municipal wastewater. Water Science and Technology, 38 (4-5), 437-442. 

Cote, P., et al. (1997). Immersed membrane activated sludge for the reuse of municipal wastewater. Desalination Proc. 1997 Workshop on Membranes in Drinking Water Production, June 1-4, L Aquila, Italy, 113, 2-3, 189-196. Elsevier Science B.V., Amsterdam, Netherlands. 

Buisson, H., et al. (1997). Use of immersed membranes for upgrading wastewater treatment plants. Water Science Technol., Proc. 1997 Int. Conf. on Upgrading of Water and Wastewater Syst., May 25-28, 37, 9, 89-95. Elsevier Science Ltd., Exeter, England. 

Yeager et al. [00] reported diffusion coefficients of water in Nafion 120 membranes containing various alkali-metal cations, determined by radiotracer measurements. In these studies, the diffusion coefficient of water was measured for fully hydrated (i.e., immersed) membranes. The water diffusion coefficient was found to be only slightly dependent on the cation present in the immersed membrane, with a... 

Okada et al. [93] have reported water transport numbers based on a measurement of the potential developed when a differential pressure is applied across a membrane contacting dilute electrolytes. For a crosslinked, sulfonated vinyl copolymer, cation-selective membrane designated CR61 AZL 386, they report a water transference number of 2.3 for the protonic form of the immersed membrane. 

O. D. Basu and P. M. Huck, Integrated biofilter-immersed membrane system for the treatment of humic waters. Water Research 38, 655-662 (2004). 

Heat solution of O.lxSSC plus 10 mM EDTA to boiling, remove from heat source and add SDS to 0.5%. Immerse membrane in the hot solution (about 1 ml/cm ) for about 15 min. 

Most of the measurements were carried out under so-called "standard state" to obtain reproducible results, i.e., the "standard swollen state" is obtained after a half-hour boiling the membranes in water, and the "standard-dry state" is obtained after drying the membranes at 107°C for 18 hrs in vacuum oven. Hereafter the measurements under the standard state are simply designated as "dry" or "swollen" state. Some measurements were carried out under nonstandard states the membranes dried at room temperature are designated as "room-temperature dry" membranes, and the specimens immersed in water at room temperature for a few days are designated as "immersed" membranes. 

The priority for the Seine Aval project is to continue the work on effluent denitrification, ainiing to increase the denitrification capacity to treat 30% of incoming effluent during dry w eather, Denitritication will be ensured by the Biost> r process. Tlie BiosepD immersed membrane bioreactor process will assure the filtration of water coming from treated sludge,... 

Membrane processes for this analysis include SWRO, BWRO, low-pressure RO (LPRO), brine recovery RO (BRO), pressurised MF/UF (pMF/UF), immersed membrane bioreactor (iMBR), cross-flow membrane filtration (XMF) and electrodeionisation (EDI). Membrane process characteristics for water treatment are detailed in Table 5.1. Typical process flow schematics of RO membrane plants are shown in Figures 5.1 and 5.2. RO/NF systems are typically multi-stage and single-pass or multi-stage and double-pass, as shown in Figures 2.21-2.23. 

The photoinitiator may be loaded on the membrane surface by adsorption or may be dissolved in the monomer solution. For example, PET nucleopore membranes were modified using BP dissolved in the monomer solution following UV irradiation of the solution and the immersed membrane (Yang and Yang 2003). It was shown that photografting occurred mainly on the top membrane surface rather than in the membrane pores. This approach is relatively simple however, its main drawback is a low local concentration of BP on the membrane surface because BP moves to the membrane surface only by diffusion. This results in a low grafting efficiency. High bulk BP concentration may cause a side reaction, such as homopolymerization. In addition, the use of monomers that do not have a common solvent with BP is limited BP is almost insoluble in water. 

Figure 5 Frequently applied dialysis setups. (A) Thin layer flow cell, (B) immersion membrane probe, (C) hollow-fiber membrane module, and (D) immersing hollow-fiber membrane probe.

A number of experimental measurement techniques are discussed, with a focus on noninvasive optical techniques such as particle image velocimetry and digital image analysis, as well as a number of academic numerical modeling tools such as discrete particle model and two-fluid model. Not only hydrodynamic aspects, such as the emergence of defluidized zones and solids circulation profile inversion, but also the effect on the bubble size distributions are discussed for wall-mounted membranes and horizontally immersed membranes. 

Background fluidization Background fluidization Background fluidization Figure 4.3 Possible membrane configurations inside fluidized beds, with waii-mounted membranes (A), vertically immersed membranes (B) and horizontally immersed membranes (C). The arrows indicate extraction or addition of gas via the membranes. Reprinted from De Jong et al. (2012c) with permission from Elsevier. 

In another work, De Jong et al. (2013) explain the modification of this setup to include up to 121 horizontally immersed membranes. Via holes in the rear wall, membrane tubes consisting of a porous cylinder with a mean pore size of 10 pm can be inserted. 

The most conspicuous aspect in this graph is the difference in the magnitude of the solid fluxes between the part with immersed membrane tubes and the top part without membranes due to the expansion of the bed in the part with immersed membranes, the sohd flux is significantly smaller than in the upper part of the fluidized bed without membranes. The presence of the membranes results in a significant decrease in the sohd velocity in the immediate vicinity of the membrane tubes irrespective whether the sohds move upward or downward. 

Cross-flow microfiltration membranes can be further subdivided into tubular and immersed-membrane types. Tubular membranes are arranged such that the raw-water source is introduced under pressure in a tube that surrounds the membrane. Typically, the permeate water proceeds from the outside of the membrane into the lumen in the center of the membrane, where the permeate is then conducted back to a manifold for collection. The solids remain on the outside of the membrane in the pressure tube and are periodically blown down from the system. 

Immersed membranes can be placed directly in a process tank where the permeate is removed through the membrane by a suction pump on the permeate collection manifold.This arrangement is possible because of the low transmembrane pressure exhibited by this type of membrane. 

Microfiltration membranes are typically periodically cleaned by backpulsing these membranes. This can be accomplished through a variety of ways, some incorporating air and some using just product water or water containing a small amount of hypochlorite. Some immersed-membrane systems also use diffused air to agitate the membranes and prevent solids from caking on the membrane surface. 

If the size of the obtained polymer-heavy metal binding is suitable, the microfiltration membranes can be applied. For example, As(V) ions have been removed by adsorption onto chitosan in a continuous stirred tank reactor (CSTR) coupled with a microfiltration immersed-membrane unit using 350 hollow organic fibers, with a cutoff of 0.2 xm and a surface area of 0.2 m (Gerente et al,... 

The emergence of immersed membrane technology has made it possible to utilize plant infrastructure, keeping capital costs down. Water treatment plants can be retrofitted with an MIEX process and immersed membranes into the existing infrastructure (Fig. 6.11). 

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