Membrane and Desalination Technologies - TCE Moodle Website

Desalination of Seawater by Thermal Distillation and Electrodialysis Technologies 531
In this chapter, the thermal distillation and ED (EDR) processes for desalination are
presented and the working mechanisms and recent advance of the same are illustrated. RO
process is also briefly presented. A comparison of these desalination technologies is given.
Other important issues, such as pre- and posttreatment processes, energy, and environmental
aspects are discussed.
2. THERMAL DISTILLATION
2.1. Introduction
Distillation is a thermal process. It is the oldest and most commonly used method
of desalination. A simple distillation process for desalination is illustrated in Fig. 12.3. The
world’s first desalination plant was operated in the mode of a multiple-effect distillation with
a capacity of 60 m 3 /d. This was installed in Curaçao, Netherlands Antilles, in 1928. Furthermore,
commercial development of the seawater distillation units took place in the late 1950s
(10). Distillation relies on the technology developed for industrial evaporation operation.
MSF, MED, and VC processes have successfully led to the widespread use of distillation to
desalinate seawater.
Product water recoveries by distillation range from 15 to 45% depending on the
operation. The water is nearly mineral free, with very low TDS content. TDS of less
than 25 mg/L is quite common and it normally rangesfrom5to50mg/L.However,this
water must be subjected to proper posttreatment, as it is too corrosive to meet the
Plastic sheet
Stove
Steam
Pure water
Vent for excess steam
Weight
Condensed water droplet
String holding plastic sheet
Small pot
Weight
Steam
Cooking pot
Fig. 12.3. Illustration of simple distillation for desalination.