Engineering Clean Water

Professor Elimelech and his student, McGinnis, next to the Forward Osmosis system at Yale. Photo courtesy of Professor Menachem Elimelech.

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We face a critical global challenge for meeting adequate and safe drinking water needs. Currently, one-third of the world’s population lives in water-stressed areas. Adding to the issue of water scarcity is that available water is often not potable. One billion people lack access to safe drinking water and two billion people lack adequate sanitation. Each year, over two million deaths result from unsafe drinking water, mostly due to preventable, water-borne diseases. For developing countries, building piped infrastructure for safe water transport to remote communities is a considerable cost. Rapid urban growth disrupts planning for and construction of new water and sanitary infrastructures. Scientists are searching for simple and low-cost inventions at the household and community levels to improve the quality of drinking water.

Elimelech explains, “To address the global water problem for all regions in the world, we need sustainable technologies that consume less energy and chemicals and have lower impact on the environment.” For twenty years, Elimelech has been working on advanced technologies for the removal of contaminants from water. His research is now going beyond the laboratory and into the global market. Oasys Water, a Yale spinoff company capitalizing on Elimelech’s research, will commercialize a new technology for desalinating water by forward osmosis.

The technology behind Oasys Water takes advantage of Elimelech’s research on forward osmosis, a low-energy osmotically-driven desalination process. Seawater is introduced across a semi-permeable membrane from a draw solution. The draw solution has a high concentration of solute and therefore a higher osmotic pressure than seawater. As a result, water flows from the seawater into the draw solution. Following this membrane-based separation procedure, the solutes in the draw solution are removed and recycled. The remaining product is clean and desalinated water.

A diagram of the forward osmosis process. Photo Courtesy of professor Menachem Elimelech.

In his laboratory, Elimelech and his students continue to study governing mechanisms for water permeation in the forward osmotic system, interfacial membrane transport phenomena, and fouling of the forward osmosis membrane.

This new forward osmosis technology has the potential to cheaply and effectively promote a sustainable global water supply. Estimates suggest that forward osmosis requires 70 to 85 percent less electrical energy than other advanced seawater desalination systems, such as reverse osmosis. The new technology would serve a crucial function not only in developing but also in developed countries. Reuse of wastewater and use of energy efficient seawater desalination in the developed world will augment water supply worldwide. In Israel, Singapore, and California, where water supplies are scarce, advanced water technologies are already being employed. Elimelech remarks, “Investors were attracted by our forward osmosis desalination technology because of the potential to desalinate seawater using much less electricity than current advanced desalination technologies.” Oasys Water, based in Boston, intends to start selling the technology in 2012.

Elimelech maintains that the future of engineering clean water is “more robust and energy efficient…membrane-based processes.” Membrane-based processes already dominate the treatment of surface waters in many parts of the world, but Elimelech anticipates expansion of the technology to wastewater recycling and seawater desalination. Recent advances in nanotechnology may be crucial to the development of more efficient technologies. Although we are not on target to achieve the goal of global access to safe drinking water, forward osmosis and other new technologies will substantially accelerate our progress towards a clean and sustainable worldwide water supply.