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NMSU researcher creates innovative method for purifying water

A New Mexico State University chemical engineering professor is developing a low-cost method for removing salt from water that will be tested at the Tularosa Basin National Desalination Research Facility.

Shuguang Deng, assistant professor of chemical engineering at New Mexico State University, is developing a low-cost method for removing salt from water. His technology could help New Mexico convert its large deposit of salt water in the Tularosa Basin to

Because much of New Mexico's water contains salt, the need for an effective, low-cost desalination process is crucial.

Shuguang Deng's project, "Integrated Reverse Osmosis and Membrane Distillation for Brackish Water Desalination," offers the promise of a low-cost process that will overcome several problems associated with current desalination methods. The project is funded by WERC: A Consortium for Environmental Education and Technology Development at NMSU.

Currently, reverse osmosis is the method of choice for removing salt from water. Reverse osmosis uses pressure to force saltwater through a membrane. Salts are left behind, producing fresh drinking water. Though cost-effective, reverse osmosis is not powerful enough to treat water with a high salt concentration and can use a lot of energy.

Thermal distillation is another process of water purification. Here, water is boiled to create water vapor and the vapor is cooled to create pure water. This process of desalination uses a lot of energy to boil the water, so it is expensive.

Deng's project combines reverse osmosis with a new technology called membrane distillation. Essentially, membrane distillation involves the transport of water vapor through a membrane, separating two liquid solutions. Because the membrane is hydrophobic, it rejects liquid water and does not let it pass through. The water is heated to create water vapor, which passes through the membrane, leaving the salts behind. The water reverts to liquid form on the other side as condensation occurs at a cooler temperature. The unit will treat one gallon of salt water per minute.

The project uses low-grade energy sources and requires significantly less energy than thermal distillation. It utilizes the advantages of reverse osmosis and membrane distillation to produce high-quality fresh water, overcoming the lack of efficiency in reverse osmosis while reducing energy and costs.

"This process is energy saving," Deng said. "We don't need to spend a lot of money and we don't need a large space."

A scale model is being developed at NMSU and then the project will be applied on a larger scale using water provided by the Tularosa Basin National Desalination Program. The Tularosa Basin National Research Facility promotes the study and development of desalination technologies to establish an effective process to produce an abundant supply of freshwater. The Tularosa Basin has a large deposit of saltwater, making the area a prime site to test the reverse osmosis-membrane distillation process.

"Most of it (the model) is done and it is promising, so we're going to scale it up and use water from the Tularosa Basin," Deng said.

With improved technologies, the abundance of saltwater in New Mexico could potentially be purified and used as a freshwater supply for residential, agricultural and industrial uses.

The WERC consortium consists of New Mexico State University, the University of New Mexico, the New Mexico Institute of Mining and Technology, Dine College and Los Alamos and Sandia National Laboratories. WERC's mission is to develop human resources and technologies that assist various levels of government and private sector companies in addressing environmental issues. For more information about WERC, visit www.werc.net or call (505) 646-2038.

"Eye on Research is provided by New Mexico State University. Today's feature was written by Cindy Remy, a communications intern at WERC. Future articles will focus on other NMSU research activities.