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Seawater desalination has been growing rapidly in the past five years, due in partto the many new membranes that are available to designers. These newmembranes have significantly improved performance, which results in lowerpermeate salinity and lower operating pressure. Recently, new low pressureseawater elements have been developed, and the optimum design with theseelements must be carefully considered. This paper analyzes the trade-offs whichexist when choosing these membranes. In cases of lower feed temperatures,which are more common in the Pacific coastal area of the USA, and lower salinities,these lower energy seawater elements can provide sufficiently low permeatesalinity, generally less than 500 mg/l. Alternatively, designers can use hybriddesigns, where higher rejection, higher energy consumption elements are used inthe front of the vessel and lower energy elements are used in the back of thevessel. This approach results in a feed pressure and permeate salinity betweenthe two. Use of these new products can result in as much as 1 kwhr/kgal of energysavings. The advantage of this type of approach is that the lower permeable leadelements will have lower flux, resulting in a more balanced element flux distribution.Alternatively, these new membranes can be used in high area configurations,which have as much as 440 ftsup2/sup of membrane area. The higher area can result inabout $0.1/gpd in capital costs savings. Thus, these new designs offer a variety ofadvantages, but detailed analysis is needed to select the optimum element andconfiguration. Includes 4 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 12File Size: 1 file , 730 KB