August 5, 2011
Solving World’s Water Shortage Will Require Improved Desalination
The need for fresh water is expanding every day and over one-third of the world's population currently inhabit areas struggling to keep up with the demand for water. Researchers estimate that by 2025, that number will nearly double.
Digging deeper or pumping water from further upstream in the water table is only a short-term solution that often leads to disputes between countries and water conservation and reuse projects have only limited effectiveness.
A new study from Yale University and the University of Notre Dame argues that seawater desalination should play an important role in helping combat worldwide fresh water shortage, once conservation, reuse and other methods have been exhausted, providing insight into how desalination technology can be made more affordable and energy efficient.
"The globe's oceans are a virtually inexhaustible source of water, but the process of removing its salt is expensive and energy intensive," said Menachem Elimelech, a professor of chemical and environmental engineering at Yale and lead author of the study, which appears in the journal Science.
"Seawater desalination is an energy-intensive process; desalinating seawater consumes significantly more energy than treating traditional fresh water sources," Phillip said. "However, these traditional sources aren't going to be able to meet the growing demand for water worldwide.
Hopefully, our paper helps provide some of the information needed to inform the decisions of policy makers, water resource planers, scientists, and engineers on the suitability of desalination as a means to meet the increasing demands for water."
In the new study, Elimelech and William Phillip, now at the University of Notre Dame, demonstrate that reverse osmosis requires a minimum amount of energy that cannot be overcome, and that current technology is already starting to approach that limit.
Instead of higher water flux membranes, Elimelech and Phillip suggest that the real gains in efficiency can be made during the pre- and post-treatment stages of desalination.
Phillip is interested in examining how membrane structure and chemistry affect the transport of chemicals across a variety of membranes. Understanding the connection between functionality and property enables the design and fabrication of next generation membranes that provide more precise control over the transport of chemical species.
These material advantages can be leveraged to design more effective and energy-efficient systems. Chemical separations at the water- energy nexus (e.g. desalination) is one area where this knowledge can be applied.
"All of this will require new materials and new chemistry, but we believe this is where we should focus our efforts going forward," Elimelech said. "The problem of water shortage is only going to get worse, and we need to be ready to meet the challenge with improved, sustainable technology."
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