SECTION III 

 INTRODUCTION 



DESALINATION PLANTS 



Large-scale desalination plants are commonplace in many tropical 

 and subtropical areas where freshwater is limited. A 1970 world- 

 wide survey by the U.S. Department of the Interior, Office of 

 Saline Water, showed a total of 686 desalting plants of 25,000 

 gallons-per-day capacity or greater. They had a total capacity 

 of 247,166,000 gallons of freshwater per day. The largest plants 

 were at Rosarita, Mexico (7.5 mgd) ; Temeuzen, Netherlands (7.6 mgd) 

 and Schevchenko, Russia (31.7 mgd). The largest plant in the U.S. 

 was the facility in Key West, Florida (2.6 mgd). 



About 98 percent of the desalination plants used the flash distillation 

 process employed by the Key West facility and most were constructed of 

 similar materials. The major difference between the Key West facility 

 and other desalination plants was the source of seawater. The Key 

 West plant obtained its seawater from deep wells rather than from 

 the sea. They benefited from this by eliminating biological fouling 

 problems and obtaining water of uniform, low temperature but were 

 penalized by the corrosive action of hydrogen sulfide present in 

 the well water. 



Within the next five years the Office of Saline Water predicts world 

 capacity for desalination will quadruple (Fig. 1). Desalination plants 

 of one billion gallons of freshwater per day capacity have been designed. 

 The ecological impact of the effluent from these plants requires immediate 

 consideration as engineering plans (including effluent discharge designs 

 and materials for construction) are already nearing completion. Small 

 modifications in outfall design and forethought about the location of 

 these outfalls may make significant differences in the ecological impact 

 of the wastes. Since heavy metals produced by internal corrosion 

 endangers marine biota, careful selection of materials for various 

 portions of the plants can have vital importance on the biological impact. 



In 1968, Westinghouse Ocean Research Laboratory began preliminary surveys 

 on the biological impact of the desalination plant at Key West, Florida 

 (Clarke et al 1970), with support of the Federal Water Pollution Control 

 Administration (now the Environmental Protection Agency). Their findings 

 prompted a more extensive biological investigation to quantify the bio- 

 logical impact and determine which constituents of the effluent were dele- 

 terious. Therefore, in July, 19 70, Westinghouse Ocean Research Laboratory 



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