Membranes in Water Treatment

Membrane technology, using reverse osmosis to treat drinking water, is a promising alternative to conventional treatment. The method is now being used for desalination in a growing number of U.S. applications, including the world's largest desalination plant that recently went on line in Yuma, Arizona. Other well-established membrane methods are nanofiltration and electrodialysis, although these techniques are just beginning to be used in the U.S. Ultrafiltration is another membrane technology that is just emerging. All are described, along with their appropriate applications for treating drinking water. There are also different types of membranes; their characteristics, such as molecular weight cutoffs, are defined. Advantages are listed, principal among them that fewer chemicals are needed. The method generates less sludge, reducing disposal problems. They also offer potential for reducing treatment plant size and thus cutting costs. A major drawback is that membranes can become fouled with materials such as iron manganese, clay, and other organic substances that physically plug the surfaces, reducing efficiency. Nonetheless, costs are becoming competitive with conventional methods and much research is now being conducted that will make membrane technology even more attractive.