Reverse osmosis design considerations

Design Considerations for RO Reverse osmosis plants are typically assembled onto carbon steel or stainless steel frames using permutations of components from the hundreds of individual standard stock items commonly available, including a wide range of membranes, each with their own range of design features and applications. 

Considerable activity has been generated on composite reverse osmosis membranes by Japanese researchers. Patent applications were recently published, for example, covering research at Teijin Ltd. on interfacially formed membranes prepared from polydiallylamines (17) and from amine adducts of trls-(glycidyl) isocyanurate (18). Both types of membranes were formed on micro-porous polysulfone supports. Kurihara and coworkers have developed a composite membrane, designated PEC-1000, which is formed by an... 

The considerations above have been utilized by various manufacturers in designing efficient ultrafiltration and reverse osmosis equipment. 

To ensure the successful design of a reverse osmosis process, several factors should be considered. These considerations encompass the feed solution, the membrane module, and the use of other processes in the pre- and post-treatment processes. A thorough knowledge of the feed stream and its components is essential to the prevention of membrane damage and product impurities. Once the feed stream is characterized and the process objective is defined, design can be initiated. 

Wild, P. M., G. W. Vickers, and N. Djilali (1997). Fundamental principles and design considerations for the implementation of centrifugal reverse osmosis. Proc. Inst. Mechanical Engineers, Part E J. Process Mechanical Eng. 211, E2, 67-81. MEP, London. 

Membrane installations generate secondary wastes that have to be taken into consideration before plant design. Reverse osmosis produces permeate, which can be discharged after radioactivity control, and retentate that can undergo further processing. Usually the retentate is not suitable for solidification and further volume reduction is necessary. 

The ionic concentration to be treated is an overriding consideration governing the cost of plant of a given design and therefore for very high ion concentrations it is foreseeable that membrane pretreatments such as reverse osmosis and electrodialysis will continue to fulfil an important role as might a more widespread revival of continuous countercurrent ion exchange. 

Bartels CR, Will M, Andes K, and long J, Design considerations for wastewater treatment by reverse osmosis. Water Science and Technology 2005, 51(6-7), 473-482. 

R. Bradley, Design considerations for reverse osmosis systems, in Z. Amjad (Ed.), Reverse Osmosis, Van Nostrand Reinhold, New York, NY, 1993, pp. 104—138. 

In practical reverse osmosis with a positive (AP — Atc), there is considerable flow of solvent from the feed to the permeate. However, the membrane is designed to reject the solute species. Thus, from the feed solution next to the membrane, solvent is continuously withdrawn through the membrane, whereas the solute species is not. This leads to a build-up of solute concentration near the membrane-feed solution interface (Figure 3.4.7) in excess of the bulk feed solute concentration C,y This phenomenon is called concentration polarization. The feed-membrane interface is now exposed to a solute concentration instead of Cif < Cfji). Consequently, the solvent and solute flux expressions in the solution-diffusion model for one solute in a solvent system are changed to... 

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