With such an extensive coastline, desalination may be the answer to the water crisis in South Africa.
Serious about ‘salt’
In principle, everyone supports the idea of desalinating seawater or
sewage wastewater to a potable level, but the real challenge is to
produce it at an economical, affordable level.
By Jacques Laubscher, technical executive at GIBB Engineering & Architecture
I
n South Africa, it seems that
whenever drought starts to bite,
talk of desalination returns to the
national debate.
The Western Cape is only now
emerging from another close scrape,
where the winter rains arrived with the
province’s dams around a dismal 10%
of capacity. Drought conditions have
become such a regular occurrence
that we need to look seriously not
only at water conservation, but at
alternative sources of potable water.
The principle of desalination is as
an ancient process. Through the ages,
sailors at sea boiled seawater and
captured the condensate to provide
drinkable, desalinated water.
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Presently, there are primarily two types
of desalination: thermal desalination,
and reverse osmosis, where saline
water is forced through a membrane
at very high pressure to remove the
saline content. Thermal desalination
is by far the most expensive method,
costing roughly four times more than
reverse osmosis. But even the latter
is still more than twice as costly as
the current conventional treatment of
surface and groundwater.
We live in an arid country — mostly
desert in fact. Our water resources are
stretched to the limit, with our few
water-rich areas being highly localised.
This is an international problem. Only
about 0.08% of the world’s water is
Water Sewage & Effluent September/October 2017
accessible for direct human use, which
means that 2.5 billion people worldwide
live in water-stressed areas.
South
Africa’s
freshwater
resources are virtually fully utilised and
are under heavy stress. It is predicted
that by 2030, freshwater demand will be
0.08%
World’s water is
accessible
for direct human use