A Feasibility Study - Aaltodoc - Aalto-yliopisto

5 Desalination
The importance of desalination is well illustrated by the former US president John F.
Kennedy: “If we could ever competitively, at a cheap rate, get fresh water from
saltwater, this would be in the long-range interests of humanity [and] really dwarf any
other scientific accomplishment” (UNDP 2006, p. 149). Presently, desalination is
producing vast amounts of pure drinking water, but it is currently not a universal
solution to the global water crisis. Desalination has progressed with huge leaps during
the past decades and is also continuing to do so (Birkett 2011). The future might well
see the vision of President Kennedy – cheap fresh water from salt water – coming to
life.
The production of fresh water from seawater can be achieved through many different
technologies, but they all have some common features. A simplified presentation of the
process is expressed in Figure 12. In general the purpose of a desalting device is to
separate saline water to fresh water (with a low level of dissolved salts) and to brine
(water, with a high level of dissolved salts). The device requires energy to operate.
Depending on the separation technology the energy needed can be thermal, mechanical,
electrical, or a combination of these (Buros 2000).
Figure 12. A simplified presentation of a desalting device (Buros 2000).
This Chapter will present the current major technologies of seawater desalination,
starting from the more traditional thermal methods and ending with the increasingly
popular reverse osmosis technology, the main membrane method. Reverse osmosis
currently has roughly 60 % of the desalination markets. From each technique, the
general operating principle will be presented, as well with some key figures of their
operation and some examples of operational facilities. The end of the Chapter will dwell
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