We need to innovate. We need to
change the paradigm. We can’t just keep on
doing what we’re doing.
That was Dr. Menachem Elimelech, who leads a Yale University team working on a forward osmosis pilot plant that has reported at ACS national meetings. Imagine a membrane
with seawater on one side and a highly concentrated solution of dissolved ammonia and
carbon dioxide gases on the other. The ammonia and CO create osmotic pressure that
2
draws the water on the other side through the membrane. Freshwater can then be recovered from the draw solution by heating it to about 136 °F so that ammonia and carbon
dioxide bubble out. They are captured and recycled to the next batch.
Greener Desalination
In addition to offering potential savings on energy, forward osmosis produces less brine
than existing desalination processes. Desalination brine is about 1. 5 times as salty as seawater, and has raised environmental concerns. The challenge to chemists and other scientists:
Forward osmosis requires membranes that are very thin, very porous, and resistant to highly
alkaline water.
Scientists are pursuing many other solutions to the energy and environmental drawbacks
of desalination. Solar energy, for instance, could substitute for fossil fuel. And the environmental impact of returning brine to the ocean can be reduced by planning and smart desolation plant placement. One approach: Locating desalination plants near wastewater treatment
or electric power plants so that brine can be diluted in the outfall streams from those plants
before entering the ocean.
Mark Shannon, Ph.D.
Meeting the Demand
These solutions will be more crucial in the future as water shortages intensify demand for
desalinated water. Dr. Wolfram Kloppmann, of French Geological Survey BRGM, described
future demand for desalination in a paper in June in Environmental Science & Technology on
fingerprinting of desalination-derived freshwater in the environment.
Julie Beth Zimmerman, Ph.D.
“Over the next decade, we will probably double desalination capacity worldwide, with
the most steep increase in the Mediterranean area and in the Middle East with a growth
rate of more than 100 percent in the Mediterranean countries.”
The challenge of meeting that demand is fostering new ways of thinking and encouraging
new approaches. Dr. Mark Shannon and his colleagues have presented some of those at ACS
national meetings, and Shannon emphasized it in an address at the U.S. Department of State
in June and to Global Challenges:
“We need to innovate. We need to change the paradigm. We can’t just keep on doing what
we’re doing. I even invoked Einstein, ‘Doing the same thing again and again and expecting a
different outcome is the definition of insanity.’ We do the same thing over and over again to
try and solve the world’s problems — and it’s not getting better. Let’s think of something else.”
Conclusion
Yes, let’s think of something else. Let’s think of these and other 2008 research advances in
chemistry paying off in the years ahead. Paying off in ways that foster a 21st-century rewrite
of Samuel Taylor Coleridge’s script. Water, water, everywhere … and every drop to drink.
Please join us at ACS for the next chapter in this ongoing saga of chemistry for life. In our
next special Global Challenges podcast, we’ll examine solutions to global warming. Today’s
podcast was written and edited by Michael Woods.
