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Last modified
1/26/2010 2:49:32 PM
Creation date
10/12/2006 3:14:49 AM
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Template:
Water Supply Protection
File Number
8210.110.60
Description
Colorado River Water Users Association
Basin
Colorado Mainstem
Date
12/12/1968
Author
CRWUA
Title
Proceedings of the 25th Annual Conference
Water Supply Pro - Doc Type
Annual Report
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<br />WATER RECLAMATION AND REVERSE OSMOSIS <br /> <br />By DANIEL C. M, CRABBE <br />E.l. du Pont de Nemours & Company, Inc. <br /> <br />NOTE: SLIDES USED IN THIS PRESENTATION HAVE BEEN OMITTED FROM PROCEEDINGS. <br /> <br />Water desalination and purification has received much attention through the ages. Until re- <br />cently, this attention has been concentrated upon pumping water out of the oceans, purifying it, and <br />in this way supplementing the world's water supply. The glamour of the project obscures the issues <br />and solutions to today's growing water problems. Government officials, Congressmen, newspapers and <br />others have been caught up in the drama of desalting the sea, but much of the population might bene- <br />fit sooner if water could be used more times rather than transported from the ocean. <br /> <br />The most optimistic figures still show a high cost of desalting sea water when compared to <br />that of treating waste water for reuse. This country and many other countries of the world are going to <br />live and work for decades-to-come, cleaning up waste streams not only to curb the pollution of our <br />lakes and rivers, but also for use in industry, for farm irrigation and for drinking. <br /> <br />Reverse osmosis is receiving increased consideration in the purification of water supplies for <br />both municipal and industrial consumption. Further down the road, agriculture may benefit from this <br />process. Present economics prohibit the use of desalted water for irrigation. However, as these costs <br />are reduced and better information on the true costs of using brackish water for irrigation is received, <br />the farm communities will benefit from reverse osmosis. <br />(SLIDE I) <br /> <br />The principles of osmosis and reverse osmosis are well known. If water containing a high a- <br />mount of dissolved material is placed in a container on one side of a suitable membrane and water <br />with a low amount of dissolved material is placed on the other side, an osmotic flow will develop and <br />the water containing the less dissolved material will flow through the membrane until the head pres- <br />sure becomes equal to the difference between the osmotic pressures of the materials. <br /> <br />Reverse osmosis is the process by which a force in excess of the osmotic force is placed on the <br />more saline water, and water with a small amount of dissolved material flows through, or permeates, <br />the membrane. The dissolved materials which cannot pass through the membrane are, therefore, con- <br />centrated. <br /> <br />For any membrane, the rate at which reverse osmosis occurs is dependent upon the area, <br />thickness and water pressure. Consideration of the membrane configuration leads to the conclusion <br />that the use of very small hollow fibers which are inherently strong, provides a maximum transfer area <br />per unit volume. <br /> <br />. <br /> <br />(SLIDE 2) <br /> <br />For a reverse osmosis process, Du Pont has developed small, hollow, cylindrical fibers. Magni- <br />fied many times, these fibers look like small tubes. <br /> <br />(SLIDE 3) <br /> <br />These fibers which are about one-third the thickness of human hair have outside diameters of <br />50 microns, and inside diameters of 25 microns. <br /> <br />(SLIDE 4) <br /> <br />In order to be useful, the fibers must be incorporated into a practical device. We have selected <br />a shell and tube configuration, similar to a single-end heat exchanger. At one end the fibers are potted <br />in a special epoxy resin which serves as the tube sheet. Inlet water enters the shell side near the head of <br />the equipment, which we call a "Permasep" permeator, and the reject or concentrated waste stream <br />exits from the other end. Water with a small amount of dissolved material flows through, or permeates <br />the membrane and travels in a counter-current direction to the concentrated waste stream. <br /> <br />(SLIDE 5) <br /> <br />-11- <br />
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