Abstract:
The origin and continuation of mankind is based
on water. Water is one of the most abundant resources on
earth, covering three-fourths of the planet’s surface.
However, about 97% of the earth’s water is salt water in the
oceans, and a tiny 3% is fresh water. This small percentage
of the earth’s water—which supplies most of human and
animal needs—exists in ground water, lakes and rivers. The
only nearly inexhaustible sources of water are the oceans,
which, however, are of high salinity. It would be feasible to
address the water-shortage problem with seawater
desalination; however, the separation of salts from seawater
requires large amounts of energy which, when produced
from fossil fuels, can cause harm to the environment.
Therefore, there is a need to employ environmentallyfriendly
energy sources in order to desalinate seawater.
Desalination is a process of removing dissolved salts from
seawater to produce fresh water for consumption. After a
historical introduction into desalination, this paper covers a
large variety of systems used to convert seawater into fresh
water suitable for human use. It also covers a variety of
systems, which can be used to harness renewable energy
sources There are two major types of desalination
technologies around the world, namely membrane
desalination and thermal desalination. The former
technology features the use of a special filter (membrane) to
produce desalinated water, whereas the latter technology
involves the boiling/evaporation of seawater to give off
water vapour which, on condensation, yields salt-free liquid
water. Only industrially-tested desalination systems are
included in this paper and they comprise the phase change
processes, which include the multistage flash, multiple
effect boiling and vapour compression and membrane
processes, which include reverse osmosis and electro
dialysis. Reverse osmosis ("RO") is a predominant form of
membrane desalination. For thermal desalination, the most
commonly adopted technologies are multi-stage flash
evaporation ("MSF") and multi-effect distillation ("MED").
RO is currently the most widely used method for
desalination. In 2012, it accounted for 63% of the
desalination production capacity worldwide, followed by
MSF (23%) and MED (8%).The paper also includes a
review of various systems that use for desalination. Finally,
some general guidelines are given for selection of
desalination and the parameters that need to be considered.
Keywords: Desalination, Reverse Osmosis, Membrane,
Multi-Stage Flash Evaporation ("MSF"), Multi-Effect
Distillation ("MED")