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Desalination: A National Perspective
or MF) pretreatment. Conventional pretreatment technologies based on coagulation and sand filtration cannot always achieve sufficient removal of foulants. Membrane-based pretreatment, particularly UF, can produce water of superior quality with very low fouling potential. Such effective pretreatment is essential for efficient utilization of future high-flux membranes.
Seawater desalination using thermal processes can be cost-effective when waste or low-grade heat is utilized effectively. Location of low-grade or waste heat resources near large water consumers may reduce the cost of heat energy and offset the higher specific energy requirements of thermal desalination when compared to RO. Hybrid membrane-thermal desalination approaches offer additional operational flexibility and opportunities for water production cost savings for facilities co-located with power plants. Thermal desalination technologies are themselves relatively mature; however, additional cost savings could be realized by improvements in materials, process configuration, and optimization of low-grade and wasxte heat resources.
Few, if any, cost-effective environmentally sustainable concentrate management technologies have been developed for inland desalination facilities. Several methods are currently available for concentrate management (e.g., surface water discharge, sewer discharge, deep-well injection, evaporation ponds, land application, and high-recovery/thermal evaporation systems to minimize the volume of waste produced), and each method has its own set of site-specific costs, benefits, regulatory requirements, environmental impacts, and limitations. Low- to moderate-cost inland disposal options can be limited by the salinity of the concentrate and by location and climate factors. Only evaporation ponds and high-recovery/thermal evaporation systems are ZLD solutions, but their costs are high for municipal application.