Reverse osmosis scheme

Nomenclature, 17 384-413 basic scheme of, 17 384-385 biochemical, 17 401-402 computerized approaches to, 17 400-401 elastomer, 21 761t enzyme, 10 258-260 for ionic liquids, 26 840-841 glossaries related to, 17 404 inorganic, 17 387-394 macromolecular (polymers), 17 403 404 organic, 17 394-401 polymer, 20 390-395 pump, 21 88 quinone, 21 236-237 reactor technology, 21 358 related to mass transfer, 15 731-737 reverse osmosis, 21 674-676 Society of Rheology, 21 704 spray-related, 23 199t systematic, 17 394... 

Relationship Between Nodular and Rejecting Layers. Nodular formation was conceived by Maler and Scheuerman (14) and was shown to exist in the skin structure of anisotropic cellulose acetate membranes by Schultz and Asunmaa ( ), who ion etched the skin to discover an assembly of close-packed, 188 A in diameter spheres. Resting (15) has identified this kind of micellar structure in dry cellulose ester reverse osmosis membranes, and Panar, et al. (16) has identified their existence in the polyamide derivatives. Our work has shown that nodules exist in most polymeric membranes cast into a nonsolvent bath, where gelation at the interface is caused by initial depletion of solvent, as shown in Case B, which follows restricted Inward contraction of the interfacial zone. This leads to a dispersed phase of micelles within a continuous phase (designated as "polymer-poor phase") composed of a mixture of solvents, coagulant, and a dissolved fraction of the polymer. The formation of such a skin is delineated in the scheme shown in Figure 11. 

Figure 18. Cross-section scheme of a composite reverse osmosis membrane...

Figure 21 Refinery wastewater recycle/zero liquid discharge scheme. Pretreatment and reverse osmosis are used to recycle water, and brine concentrator and crystallizer are used to treat the rejects to achieve zero liquid discharge. (From Ref. 78.)...

Reverse osmosis is a process used by some plants to remove dissolved salts. The waste stream from this process consists of reverse osmosis brine. In water treatment schemes reported by the industry, reverse osmosis was always used in conjunction with demineralizers, and sometimes with clarification, filtration, and ion exchange softening. 

Another scheme proposed for collecting enough concentrate for animal studies is shown in Figure 1. In this scheme for concentrating 135 gal of water to a 5-gal methylene chloride concentrate, reverse osmosis is used to reduce the initial 2000-gal volume of water to 135 gal, and the CLLE is used to further concentrate the retentate to 5 gal for biological testing. The LLE portion of this scheme was simulated in a set of CLLE evaluation experiments. The concentration factor from 135 to 5 gal is 27 1, which was easily attainable with the CLLE units. The water-to-solvent ratio in the extractors was 10 1, and the additional volume reduction was achieved by solvent distillation in the distillation chambers of the CLLE units. 

The cross-, co- and counter-flow schemes are illustrated in Figure 4.17, together with the concentration gradient across a median section of the membrane. It follows from Figure 4.17 that system performance can be improved by operating a module in an appropriate flow mode (generally counter-flow). However, such improvements require that the concentration at the membrane permeate surface equals the bulk concentration of the permeate at that point. This condition cannot be met with processes such as ultrafiltration or reverse osmosis in which the permeate is a liquid. In these processes, the selective side of the membrane faces the... 

Figure 5.22 Flow scheme showing the pretreatment steps in a typical seawater reverse osmosis system [50]...

A simplified flow scheme for a brackish water reverse osmosis plant is shown in Figure 5.24. In this example, it is assumed that the brackish water is heavily contaminated with suspended solids, so flocculation followed by a sand filter and a cartridge filter is used to remove particulates. The pH of the feed solution might be adjusted, followed by chlorination to sterilize the water to prevent bacterial growth on the membranes and addition of an anti-sealant to inhibit precipitation of multivalent salts on the membrane. Finally, if chlorine-sensitive interfacial composite membranes are used, sodium sulfite is added to remove excess chlorine before the water contacts the membrane. Generally, more pretreatment is required in plants using hollow fiber modules than in plants using spiral-wound modules. This is one reason why hollow fiber modules have been displaced by spiral-wound systems for most brackish water installations. 

Figure 5.27 Flow scheme showing the use of a reverse osmosis system to control nickel loss from rinse water produced in a countercurrent electroplating rinse tank...

Ilias and Govind [1993] also used the CFD approach to solve coupled transport equations of momentum and species describing the dynamics of a tubular ultraflltration or reverse osmosis unit. An implicit finite-difference method was used as the solution scheme. Local variations of solute concentration, u ansmembranc flux and axial pressure drop can be obtained from the simulation which, when compared to published experimental data, shows that the common practice of using a constant membrane permeability (usually obtained from the data of pure water flux) can grossly overestimate... 

Figm-e 32.7 shows the scheme of the solution proposed by the authors for treating radioactive liquid wastes from RIA laboratories. Since part of the radioisotope is in ionic form [5], reverse osmosis can be used for radioisotope removal. But before the application of reverse osmosis, a pretreatment is required. It consists of the following two stages ... 

Figure 32.11 shows a scheme of the RO plant for the treatment of the Cs-contaminated liquids. It was equipped with two kinds of spiral wound reverse osmosis membranes high-pressure (HP) and low-pressure (LP) membranes. Before flowing through the membranes, the feed was pretreated using 5 pm sleeve hlters and 0.45 pm cartridge hlters. 

Most of the earth s water resides in the oceans, as seawater. For some regions, this is the nltimate source of fresh water for public and commercial use. Conversion of seawater to fresh water requires the separation of more-or-less pure water from an aqueous solution containing dissolved solute species. About 65% of such conversion is currently done by distillation schemes. But another 30% is effected by reverse osmosis. Central to an understanding of osmotic separations are the concepts of osmotic equilibrium and osmotic pressure, the topics of this section. 

In practice, pressure differences significantly greater than FI are used to effect osmotic separations. For example, seawater lias an osmotic pressure of about 25 bar, but working pressures of 50 to 80 bar are employed to enhance tlie rate of recoveiy of fresh water. A feature of such separations is tliat tliey require mechanical power only, for pumping the solution to an appropriate pressure level. Tliis contrasts with distillation schemes, where steam is tlie usual source of energy. A brief overview of reverse osmosis is given by Perry and Green.- ... 

Seawater is to be desalinized by reverse osmosis using the scheme indicated in Fig. P2.74. Use the data given in the figure to determine ... 

For dilute feeds, consider options for preconcentrating the feed to reduce the volumes of feed and solvent that must be handled by the extraction operation. Consider evaporation or distillation of a high-volatility feed solvent or the use of reverse osmosis membranes to concentrate aqueous feeds. (See Hybrid Extraction Processes under Commercial Process Schemes. )... 

A variety of control schemes can be incorporated in the design of a reverse osmosis plant. However, this subject is beyond the scope of this manual. 

Scheme 40 describes the second part of the Hoechst Marion Roussel process of 7-AC A (129) manufacture - the first enzymatic transformation has already been described in Scheme 6. Glutaric acid derivative 20 is now subjected to treatment with immobilized Pseudomonas sp, cu-amidodicarboxylate amido-hydrolase (recombinant in Escherichia coli). The enzyme catalyzes the chemo-and stereoselective hydrolysis of the amide and gives the free amine 129 in reasonable yield and optical purity. The whole process has also been established in several other companies, with minor modifications. Anbics, for example, is presently setting up a fermentation process with its subsidiary Bioferma Murcia in Spain for the production of 7-AC A. A typical isolated yield of 82% has been reported for 129, which can be further optimized to >85% by applying techniques such as reversed osmosis on the production scale [115].

As the population of the Sunbelt areas of the United States increases, more demand will be placed on the limited supplies of fresh water there. One obvious source of fresh water is from the desalination of seawater. Various schemes have been suggested, including solar evaporation, reverse osmosis, and even a plan for towing icebergs from Antarctica (remember that pure... 

While membrane processes have infiltrated many process schemes, prohahly the most extensive replacement has been in the area of water treatment. For example, reverse osmosis has largely replaced distillation/evaporation for the production of drinking water from seawater [41,42]. Clearly, with the right mix of material properties, efficient process designs, and economic drivers, energy-efficient membrane processes can replace conventional thermally driven separation processes. Later in this chapter, desalination will be a featured example. 

Scheme of an integrated membrane process for the production of concentrated fruit juices. UF = ultrafiltration RO = reverse osmosis OD = osmotic distillation. 

Integrated membrane process scheme for cheese whey treatment. MF = microfiltration UF = ultrafiltration NF = nanofiltration RO = reverse osmosis. 

The flow scheme of these facilities is very similar to the one of a conventional water supply facility which treats surface water (in spite of the very different use). It usually consists of a physicochemical treatment (to reduce pollution associated with the colloids that escape from the secondary clarifiers of the WWTF) and a disinfection unit (to remove pathogens and prevent health issues related to the wastewater reuse). The first treatment follows a four-stage scheme coagulation, flocculation, clarification, and filtration. Membrane technology (i.e., reverse osmosis or electrodialysis) is sometimes proposed... 

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