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<br />w <br />en <br />o <br />CO <br /> <br />Operational Design Parameters Considered <br /> <br />1. Feed Water Salt Concentration <br />2. Feed Water Temperature <br />3. Product Water Quality <br />4. Energy <br />5. Feed Water Source <br />6. Reject Disposal <br />7. Site Location <br />8. Environmental Factors <br />9. Pl ant Investment and Operating Costs <br /> <br />Process Selection Conclusions <br /> <br />Based on the preceding parameters and co~parisons, the ion exchange process <br />is not considered applicable to the'Yuma'TDesalting Plant. Specifically, <br />feed water salinities are excessive, as are chemical disposal requirements <br />by comparison with distillation and membrane processes. It is further <br />concluded that distillation processes would be more expensive than the <br />membrane processes. Electrodialysis and reverse osmosis processes are, <br />therefore, technically and economically preferred for the Yuma Desalting <br />Plant, ' <br /> <br />B, Membrane Plant Operating Experience <br /> <br />During the past several 'years, the number of membrane desalting facilities <br />in commercial operation has grown tremendously. The Office of Water <br />Research and Technology's "Desalting Plants Inventory Report No, 5" lists <br />a total of 370 membrane plants having a capacity of 25,000 gallons or more <br />per day worldwide as of January 1, 1975, i/ <br /> <br />On May 16, 1974, DSS Engineers, Inc., was authorized by the Office of <br />Water Research and Technology, under Contract No. 14-30-3275, to review, <br />analyze, and summarize the design, operation, and maintenance of 11 com- <br />mercial membrane desalting plants. These plants ranged in size from <br />2,500 gal/d to 2.0 Mgal/d and included four electrodialysis and seven <br />reverse osmosis installations. In the concluding report, emphasis is <br />placed on operating experience and problems, including brackish water <br />supply and pretreatment, membrane scaling and fouling, equipment and <br />material failures, and field modifications. Information on six of the <br />larger plants includes performance and production 'cost analyses over <br />extended operating periods. <br /> <br />Several operating plants were visited and analyzed by Government personnel <br />during preliminary investigations for the Yuma Desalting Plant. Conclusions <br />extracted from the DSS report were generally corroborated by visits by <br />Government personnel, <br /> <br />11 This has increased to over 700 plants as of thebeginnin9 of 1977. <br />10 <br />