Membrane Type and Configuration

Table 16.2 Typical characteristics of different types of membrane types and configurations.

Membrane treatment plants have recently become more common, with a wide variety of membrane types and configurations being used (Fig. 3). Each membrane system will generally utilize pretreatment to remove large particles, to adjust pH, disinfect, and/or minimize scaling. 

This volume Is divided Into three sections theory, carrier chemistry, and applications. The theory section Includes chapters which thoroughly describe the theory and analysis of various liquid membrane types and configurations (107-110) The carrier chemistry section contains two articles on the use of macrocycles for cation separations (111-112). The applications section begins with a survey article which thoroughly reviews the liquid membrane applications In the literature and discusses both potential and commercial aspects of liquid membrane technology. The remaining articles discuss both gas phase (113-115) and liquid phase transport (116-117). 

Gleaning. Fouling films are removed from the membrane surface by chemical and mechanical methods. Chemicals and procedures vary with the process, membrane type, system configuration, and materials of constmction. The equipment manufacturer recommends cleaning methods for specific apphcations. A system is considered clean when it has returned to >75% of its original water flux. 

Bodzek, M. and K. Konieczny (1998). Comparison of various membrane types and module configurations in the treatment of natural water by means of low-pressure membrane methods. Separation Purification Technol, 14, 1-3, 69-78. 

A wide range of membrane configurations is used with each type having its own unique characteristics. Consequently the choice of the right membrane material and configuration for a specific application can be complex. 

Interestingly, new membrane-type reactor configurations are currently being considered in order to remove H2O in-situ and thereby alleviate somewhat the effects of H2O on activity, as well as decelerate the deactivation rate for these catalysts [36,37]. 

Based on the membrane design and configuration, there are three types of dialyzers available. The design of the membrane is crucial to determine the efficiency of the dialysis (how much and how sufficiently the blood can be filtered). The basic membrane designs for dialyzers are hollow fiber, parallel plate and coil dialyzers, and each one has its own disadvantages and advantages over the other, but all of them ultimately have the same function. 

Diversity of Membrane Eiements and Configurations Currently, all membrane manufacturers offer their own design, size, and configuration of membrane elements and systems. The membrane systems differ by the type of filtration driving force (pressure versus vacuum), the size of the individual membrane elements, the size of the membrane vessels, the configuration of the membrane modules, the type of membrane element backwash, and the type of membrane integrity testing method and other factors. 

TFF membrane systems generally use a common feed distributed among parallel modules with a collection of common retentate and common permeate streams. In some applications, it is also useful to plumb TFF modules with the retentate in series where the retentate flow from one module provides the feed flow to the next module. This type of configuration is equivalent to increasing the length of the retentate channel. Permeate flows may or may not be plumbed together. 

Hollosep High Rejection Type is characterized by Cellulose Tri Acetate (CTA) hollow fiber with dense membrane structure and high salt rejection, and also by the module configuration favorable for uniform flow of feed water through hollow fiber layers (5 ). These features suggest that Hollosep may be operated under the conditions of higher recovery ratio compared to conventional conditions. 

Among the configurations described in that paper, the irradiation carried out on the recirculation batch seems very promising since it allows high irradiation efficiency and high membrane permeate flow rate to be obtained and also it is possible to select the membrane type depending on the photocatalytic process under study. 

The membrane module and design will obviously depend on the type of membrane used. The flat-sheet membranes are commonly constructed in a plate-and-frame configuration or as spiral-wound (SW) modules. F1F/CT/MTmembrane types are commonly manufactured into bundles that are installed in housing units or designed to be unconfined in the fluid, that is, immersed units. The membranes are... 

Figure 16.2 Examples of membrane types (FS and HF) and typical installation/configuration.

In Table 16.2 some of the typical characteristics of the various types of membranes and configurations are given. In MBR systems SW membrane modules are not used as the channels within the spiral are prone to clogging when the feed water has high suspended-solids concentrations. Tubular membrane systems are not common either as they tend to become very expensive due to the low area to volume ratio. Commercial MBR systems today are normally based on immersed FS configurations or H F/CT configurations. 

Process Descriptions Selectively permeable membranes have an increasingly wide range of uses and configurations as the need for more advanced pollution control systems are required. There are four major types of membrane systems (1) pervaporation (2) reverse osmosis (RO) (3) gas absorption and (4) gas adsorption. Only membrane pervaporation is currently commercialized. 

All types of membrane in this configuration are fashioned into mod-nles by potting the ends with a curable liquid (Figs. 22-49 and 22-50). 

The geometry of the membrane reactor and the relative locations and flow directions of the feed, permeate and reientate streams all play important roles in the reactor performance. The simplest, but not efficient, membrane reactors consist of disk or foil membranes with a flow-through configuration [Mischenko et al., 1979 Fumeaux et al., 1987]. The same type of membrane reactor can also be consu cted and operated in the more common crossflow mode. 

Membranes with non-traditional surfaces have been suggested [Gryaznov et al., 1975]. Pd-based membranes in the form of cellular foils were fabricated and used to carry out a hydrogen-consuming and a hydrogen-generating reaction on the opposite sides of the membrane. The foils have oppositely directed, alternate projections of hemispherical or half-ellipsoidal shapes. This type of configuration, in principle, provides uniform... 

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