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<br />w <br />0) <br /><::> <br />c..., <br /> <br />-~ <br /> <br />II. <br /> <br />DESALTING COMPLEX UNIT (STUDIES UNDERTAKEN) <br /> <br />With 'the direction provided by Publ ic Law 93-320 to construct a desalting <br />plant as the permanent solution, a number of studies were required to pro- <br />vide data for design. The unprecedented size and need for high reliability <br />lead to intensive studies by the Government as well as consultants, These <br />studies included process selection, operating experience, field testing, <br />opti~fzation of available equipment, and definitive size requirements, <br />In aqdition, questions of power supply and reject stream replacement had <br />to be addressed. The more important studies are summarized below. <br /> <br />A. ~Desalting Process Selection <br /> <br />All major desalting processes were considered for the Yuma Desalting <br />Plant. Considerations for process selection were based on Colorado River <br />flowiand quality data, salinity concentrations, volume of water to be ; <br />proc~ssed, project criteria, constraints inherent within the desalting . <br />proc~sses themselves, and Public Law 93-320's stipulation to use advanced. <br />technology commercially available. <br /> <br />Broaq categories of available desalting processes include distillation, <br />crystallization, ionic, and liquid-liquid extraction. The distillation <br />category includes multiple-effect evaporation, multiple-stage flashevap- <br />oration, vertical tube evaporation, solar, vapor compression, and super~ <br />critical distillation, The crystallization processes include freeze <br />sepa~ation and hydrate separation. Ionic processes are ion ex~hange, <br />electrodialysis, reverse osmosis, transport depletion, piezodialysis, <br />electrochemical, and biological systems. <br /> <br />- ./ <br />,c <br /> <br />!~ <br /> <br />; <br /> <br />:i <br /> <br />Few Qf the processes have been commercially applied, and since this was <br />a basic criteria for the selection of the desalting process, the list of <br />app11cable processes was reduced to: <br /> <br />,1, Distillation Processes - multiple-effect, multiple-stage flash <br />:(MSF), vertical tube evaporation (VTE), and vapor compression (VC); <br />,and <br /> <br />2, Ionic Processes - ion exchange (IX), electrodialysis (ED), and <br />reverse osmosis (RO), <br /> <br />Process Performance Requirements <br /> <br />Public Law 93-320. in Section 101.(b}(2), specifies a daily treatment <br />capabty of approximately 129 million gallons, not le,ss than a 70-percent <br />prod~ct water recovery ratio, and not less than a 90-percent reduCtion of <br />the dissolved solids in the feed water. The water quality differential <br />requ~rement stipulated in 'Minute No. 242 is a factor which must be met <br />throllgh the operational capability of a manufacturer's equipment. <br /> <br />9 <br /> <br />:J.' _~ <br /> <br />