Roughly 47% of desalination plants use
thermal desalination, with the balance
being reverse osmosis plants. Thermal
desalination is mainly used in the
Middle East, where fossil fuel energy
sources are easily available to drive
power plants.
One of South Africa’s hopes for a
large-scale desalination plant would
be a desalination plant linked to the
Koeberg nuclear power plant, where
the water used in the plant’s cooling
process can be repurposed as a
source for desalination.
At present, Koeberg returns its
coolant water to the ocean, with it
being about 10 degrees warmer than
the ocean.
The economics of desalination
involve a supply cost, usually made
up of capital costs; operation and
maintenance costs; environmental
costs; and transportation costs.
Besides the Koeberg option,
reverse osmosis desalination has been
the process of choice in South Africa.
Currently there are a small number of
operational desalination plants, with
the largest in Mossel Bay supplying
about 10Mℓ a day to the municipality
and another 5Mℓ a day to PetroSA.
To contextualise, Cape Town
recently brought its water consumption
down to 685Mℓ a day.
One of South Africa’s hopes for a large-scale
desalination plant would be a desalination plant
linked to the Koeberg nuclear power plant, where
the water used in the plant’s cooling process can be
repurposed as a source for desalination.
Water Sewage & Effluent September/October 2017
23
Water produced
by Mossel Bay
desalination plant
Desalination options
10Mℓ p/d
50% higher than current levels. Water
is intimately linked to our economy: a
decrease of only 1% in the quality and
the usability of water in South Africa
may cost 200 000 jobs, nearly 6% in
disposable income per person, and 5%
or R1.8-billion in government spending.
Our national water resource
strategy says that the national water
deficit by 2025 will be more than
240 000Mℓ per year. This is the shortage
that desalination seeks to fill.
Jacques Laubscher, GIBB
technical executive: Integrated
Infrastructure Services Sector.
Already, Cape Town is looking to the
private sector. Koeberg, if it gets on
stream, could eventually provide
anything from 150 to 450Mℓ/day —
up to two-thirds of Cape Town’s daily
water needs.
eThekwini is looking at building a
100Mℓ/day plant, combining seawater
with wastewater, which is a sensible
thing to do. Other coastal communities
are also looking at reverse osmosis
desalination plants.
Seawater
desalination
can
increase and sustain a country’s
coastal freshwater supply and
thereby sustain economic growth.
The capacity for seawater reverse-
osmosis desalination is growing at
approximately 14% per year, though it
still accounts for only 1% of the world’s
freshwater supply.
Unfortunately, technology has not
yet caught up with demand, despite
significant investments in research
and development around reverse-
osmosis technology.
I trust that science will be able
to develop a viable solution, though.
Then it will be up to the policy experts
to come up with a cross-subsidisation
model that makes water affordable to all.
The leader at this stage in desalination
is Israel, now desalinating around
582 000Mℓ of water a year. But
technology everywhere is catching
up. Government recently announced
a partnership with Iran to develop
desalination plants near coastal
communities to boost water supply.
A South African-based global
desalination company in Cape Town
recently submitted a white paper to
the city at the height of its drought,
proposing the rolling out of mobile 20Mℓ
reverse-osmosis desalination plants
within four months, and in parallel
developing a larger desalination plant
that could deliver 450Mℓ per day in a
public-private partnership.
Desalination
technology
has
improved, and the associated energy
costs have decreased to the point
where it must be taken seriously. The
question is no longer ‘Is desalination
feasible?’ but ‘Is it feasible not to
use desalination?’ u