A Review of Desalination Processes and Product Water Costs

Abstract

At the present time the Office of Saline Water is conducting research and development in three basic desalination process areas. These are distillation, membrane, and crystallization. Processes within these areas include multistage flash distillation, vertical tube evaporation, vapor compression, reverse osmosis, electrodialysis, and vacuum freezing. The Office of Saline Water has in operation for developmental purposes, plants with capacities up to approximately 2.5 million gallons per day. These plants are located at five major test stations in the United States. On the basis of test results, analytical studies, and supporting investigations, water costs have been reduced significantly over the past five years. Technological developments have resulted in a 25% reduction in water costs for distillation processes desalting seawater and a reduction by a factor of 3 for reverse osmosis processes desalting brackish water considering a fixed plant size. Coupling of improved system technology with increasing plant size results in water costs that are foreseen to be competitive with alternate means of supplying freshwater to major water consuming areas.