Chemical Engineering September 2010 - 24

Newsfront
SOLAR DESALINATION
W
orldwide, more and more people are obtaining drinking
water either from the sea or from increasingly salty inland
sources. Analysts at Global Water Intelligence, an industry
service, estimated that in 2008, desalination facilities around the
world produced nearly 12-billion gallons of water each day. This
amount is expected to more than double by 2016. The bulk of this
amount is attributable to the Arab countries around the Persian
Gulf. Other countries such as Spain, France, Greece and Italy are
also turning to desalination. While most large desalination plants
are fueled by oil or gas, smaller and medium-sized plants can run
partly or even entirely on renewable energies.
" Often people in these plants don't know how reliable and efficient
solar-powered desalination plants, or wind-powered and,
perhaps someday tidal-energy-driven plants, work, " says Marcel
Wieghaus of the Fraunhofer Institute for Solar Energy Systems
(ISE; Freiburg, Germany; www.ise.fhg.de). The European ProDes
initiative, of which ISE is a member, intends to change that by
conducting a study of examining how renewable energies can be
harnessed more effectively in the future to transform seawater and
brackish water into drinking water.
ProDes, which stands for Promotion of Renewable Energy for
Water Production through Desalination, has established an array
of processes for desalinating seawater and brackish water. Currently
most European desalination plants rely on reverse osmosis,
where high-pressure and semi-permeable membranes separate
water from salt and unwanted organic constituents. Plants operating
on conventional energy forms deliver around 400,000 m3/d
of drinking water. When it comes to desalination plants running on
renewable energy, the spectrum ranges from simple solar distillation
plants with a capacity of a few liters a day to wind-powered
reverse osmosis plants capable of desalinating nearly 2,000 m3.
Ultimately the best technology for the task depends on the salinity
of untreated water, the local infrastructure and the quantity of water
required. " The more remote the location, the more worthwhile and
profitable it is to use plant systems run on renewable energy and
to set up a water treatment operation that is not dependent on an
external energy supply, " explains Weighaus. He and a team of
researchers have installed solar-powered desalination plants on
the Canary Islands of Gran Canaria and Tenerife.
verse osmosis modules with standard
pre-treatment and post-treatment
products, it has the multiple effect of
reducing energy use, reducing costs,
increasing availability through the
use of products that are proven to
work together and shorter schedules
and start up times. "
Brad Biagini, a product manager
with Veolia Water Solutions and
Technologies (Cary, N.C.) agrees that
all-in-one treatment technologies are
efficient solutions. For example, the
Amdro from Veolia, which he says was
initially developed for water treatment
in the phosphate fertilizer industry, is
a reverse osmosis technology operated
in double-pass mode. By combining
the company's Actiflo high-rate clarification
process with filtration, RO and
In a similar vein, IBM (Armonk, N.Y.) and the King Abdulaziz City
for Science and Technology (KACST) (Riyadh, Saudi Arabia) are
collaborating to create a water desalination plant powered by solar
electricity, which could significantly reduce water and energy costs.
A new, energy efficient desalination plant with an expected production
capacity of 30,000 m3/d will be built in the city of Al
Khafji to serve 100,000 people. KACST plans to power the plant
with the ultra-high concentrator photovoltaic (UHCPV) technology
that is being jointly developed by IBM and KACST. This technology
is capable of operating a CPV system at a concentration greater
than 1,500 suns. Inside the plant, the desalination process will
hinge on an IBM-KACST developed technology, a nanomembrane
that filters out salts as well as potentially harmful toxins in water
while using less energy than other forms of water purification.
According to KACST scientists, the two most commonly used
methods for seawater desalination are thermal technology and reverse
osmosis, both at a cost ranging from 2.5 to 5.5 Saudi Riyals
per cubic meter. Combining solar power with the new nanomembrane,
the project may significantly reduce the cost of desalinating
seawater at these plants.
" Currently Saudi Arabia is the largest producer of desalinated
water in the world and we continue to invest in new ways of making
access to fresh water more affordable, " says Dr. Turki Al Saud,
vice president for research institutes, KACST.
Because over 97% of the world's water is in the oceans, turning
salt water into fresh water cost effectively and energy efficiently
offers tremendous potential for addressing the growing worldwide
demand for clean water. One of the most efficient means of desalination
is reverse osmosis. But there are obstacles to unlocking this
reserve - principally biofouling, degradation by chlorine and low
flux challenges. The joint research focuses on improving polymeric
membranes through nanoscale modification of polymer properties
to make desalination much more efficient and much less costly.
" Our collaborative research with KACST has led to innovative
technologies in the areas of solar power and of water desalination, "
says Sharon Nunes, vice president, IBM Big Green Innovations.
" Using these new technologies, we will create energy-efficient
systems we believe can be implemented across Saudi Arabia
and around the world. "
❏
WATER TREATMENT
PROVIDERS
BWA Water Additives
www.wateradditives.com
Dow Water and Process Solutions
www.dowwaterandprocess.com
GE Water and Process Technologies
www.gewater.com
IBM
www.ibm.com/smarterplanet/water
Siemens Water Technologies
www.water.siemens.com
Veolia
www.veoliawaterst.com
ion exchange, the technology generates
high-quality effluent with minimum
pre-treatment requirements.
Similarly, the company's OPUS technology
uses a reverse osmosis process
operated at an elevated pH. By com24
CHEMICAL ENGINEERING WWW.CHE.COM SEPTEMBER 2010
bining a proprietary high-rate chemical
softening process, known as Multiflow
with filtration, ion exchange and
reverse osmosis, this technology generates
high quality water with a low
waste volume.
And GE Water's Propak NA Series,
which was designed for industrial applications
in boiler feed, combines ultrafiltration
hollow-fiber membranes
to take out solids with spiral wound
RO membranes to take out dissolved
salts on a single skid. " Being on one
skid saves on footprint, and because
they aren't buying two separate systems,
it also saves on capital costs. Operational
cost savings can also be had
because the systems are optimized to
work together. "
■
Joy LePree
http://www.ise.fhg.de http://www.wateradditives.com http://www.dowwaterandprocess.com http://www.gewater.com http://www.ibm.com/smarterplanet/water http://www.water.siemens.com http://www.veoliawaterst.com http://WWW.CHE.COM
Chemical Engineering September 2010

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