Transcript Slide 1

SustainableEngineering@Edinburgh
Group 7: DESALINATION - A SUSTAINABLE OPTION?
By:
Matthew
Harvey
(0679153);
Richard
Lea
(0569383.);
Callum
Kerr
(0561778);
Gary
Britton
(0789271)
INTRODUCTION
IMS3/MSFM3 Sustainability Module, March 2008
Since the 1950’s the world’s population has doubled but at the
SUSTAINABILITY PROBLEMS
same time the amount of fresh water hasn’t changed.
This problem is only set to worsen as population continues to rise
and climate change affects the amount of fresh water available
each year. Regions of the world will no longer be able to rely solely
on fresh water sources to provide drinking water.
Desalination has been a
source of fresh water
since the 1950’s in the
Middle East. But is
desalination a sustainable
option
for
countries
around the globe as water
scarcity becomes a bigger
problem?
INSTITUTE’S
POLICY
DESALINATION METHODS
Reverse Osmosis.
Uses semi-permeable
membranes
to separate fresh water in
one chamber from brine.
Applying pressure in
excess of the osmotic
pressure to the brine,
fresh water will pass in the
reverse direction, i.e. out
of the brine.
Impingement and entrainment of organisms at the sea water intake of
large volume plants.
 High energy use required for plants, especially plants using thermal
methods. Energy usually comes from fossil fuels which is a finite
source.
 Disposal of high concentrate brine solution, post-process. Brine is
double salinity of normal sea conditions. Which can seriously affect
the marine environment.
Distillation.
Involves evaporating saline water to
obtain pure water by condensing the
vapour.
 R.O uses 4kWh/m3 (site specific) compared to 13kWh/m3 for
MSF (distillation).
 R.O has a unit cost of $0.5/m3 making it close to matching
cheaper water recycling and re-use alternatives.
 R.O is becoming the leading desalination method due to it’s
lower energy use making it the more sustainable method.
“While seawater desalination is
already a well-established water
source in these regions [Middle
East], the era of large-scale
desalination projects is only about
to start in other parts of the
world.”
ENERGY PROBLEMS
All desalination methods require a large
energy input, historically coming from
fossil fuels. With sources diminishing
across the globe future plants will need to
look at sustainable alternatives. Possible
sources are:
Wind power
Photovoltaic
Nuclear (good for large scale plants)
Tidal
FUTURE DEVELOPMENT
Australia – 2 year drought has forced
Government to consider desalination.
Projects in Perth and Sydney combine plants
with renewable energy sources.
America – Florida, Texas and California all
implementing desalination. Florida has the
Tampa Bay plant with a 25mgd capacity.
Spain - Looking to double its already large
desalination capacity within the next year.
Have a large influence
on industrial and
public support. The
EU:
 Recognise the need
for alternative water
sources
 Have a weak stance
on fresh water as a
basic human right.
 Has expensive
safety checks for
intake water
preventing large scale
desalination.
 Influence from WWF,
who sway public
opinion by taking a
stance against
desalination.
 Institute support
would allow greater
research into
desalination as a
sustainable water
source.
SUSTAINABLE SOLUTIONS
Co-location with power plants.
 Desalination Plant located by power plant
 Uses existing water intake infrastructure of
power plant
 Brine discharged into power plant outflow,
diluted due to large volume of water flowing
through out-take.
 Other solutions are using long pipes to
discharge brine into deep sea areas away from
the coast.
CONCLUSIONS
1. Desalination is on the rise around the
world.
2. Need proper measures for planning and
running of large scale desalination plants
3. Process still requires high energy input, so
often relies on fossil fuels.
4. New desalination plants will need to
incorporate sustainable energy sources.
5. Research is needed into the impact of brine
disposal on the marine environment.
REFERENCES
S. Lattemann, T. Höpner (2008) “Environmental impact and impact
assessment of seawater desalination” Desalination 220 1-15.
American Water Works Association(2006) Desalination of Seawater and
Brackish Water, Denver
Rachel Einav, Kobi Harussi, Dan Perry (2002)
“The footprint of the desalination processes on the environment”,
Desalination 141-154