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Water: What are some ways to obtain safe drinking water?

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  1. Water: What are some ways to obtain safe drinking water? Mercer University School of Engineering Professional Practices, Dr. Davis J. Walsh

  2. What’s wrong with our water today? • Some contaminants of our water today: • Lead • Radon • Nitrates • Parasites • Traditionally, chlorine has been used to eliminate these contaminants • Problems with chlorine: • It reacts with decaying organic matter • This causes cancer causing chemical byproducts

  3. One way the Army is providing water to its soldiers • New technology being tested by the Army • Turns exhaust in Humvees to drinking water • Five part system: • Catalytic converter-device in all modern vehicles that oxidizes the toxic organic compounds not combusted by the engine • The army has enlarged its surface area so it takes longer for the fumes to pass through it • This makes it cleanse the fumes more • Heat exchanger • Refrigerates fumes and causes them to condense • Treatment tanks • Bed of six activated-carbon and ion-exchange filters the liquid goes through

  4. Exhaust to drinking water • Water-Quality Sensor • Checks cleanliness of the water • Storage Tank • Chlorine is added to purify water • Held in a 5 gallon tank on rear • Water comes through a spigot • Water goes through air conditioning unit to chill and remove chlorine taste

  5. Two ways to purify water: UV and desalination • UV light • Currently 3000 to 5000 systems • Useful in wastewater • Few official regulations exist for performance-related criteria for UV units for drinking water

  6. UV light continued • How it works: • Proteins, phenols and humic material that contaminate water absorb the rays and die • Destroys all bacteria and viruses • Made of multiple standard high-quality UV lamps, sealed within quartz tubes or sleeves Photo courtesy of Islandnet.com

  7. Two methods of desalination: reverse osmosis and electro dialysis • Reverse Osmosis-membrane process for desalting water • Uses hydrostatic pressure to drive water through a semi permeable membrane, which means only selected things can go through the membrane • Pure water comes out at near atmospheric pressure • Waste is at original pressure • The figure below illustrates how this system works

  8. Desalination techniques continued: Electro dialysis • Electric energy is used to transfer ionized salts from feed water through membranes, leaving behind purified product water • Salts are ionic, so cation and anion-selective membranes are placed, alternately between two electrodes • This means the salt particles have a charge and they are attracted to the electrodes so they can be removed • Three elements: • Supply of pressurized water • Membrane stack • DC power supply • A rectifier converts alternating current to direct current • Used on membrane stack • Energizes ions and causes them to move through selective membranes

  9. How can UV light and desalination be useful? • UV light • It is an environmentally safe, nonchemical, physical process that produces no toxic side effects • The equipment is easy to operate and maintain • There can be no overdosing • No residue left • Very quick; only a few seconds while chlorine takes ¼ to ½ and hour • Desalination • Uses no chemicals • Enables salt water to be harvested for fresh drinking water • Also no overdosing or residue left

  10. References http://www.islandnet.com/~tiger/Tiger/UV/UV_pics/Trojan/diagram.jpg Keats, J. (2006, January 16). Converting tailpipes into water fountains. Popular Science. Retrieved March 16, 2008, from http://www.popsci.com/scitech/article/2006-01/converting-tailpipes-water-fountains Masschelein, W. J. (2002). Ultraviolet light in water and wastewater sanitation. Boca Raton: CRL Press LLC. Montgomery, J. M. (1985). Water treatment principles and design. Canada: John Wiley & Sons, Inc. 225-235. Spellman, F. R. (1999). Choosing disinfection alternatives for water/wastewater treatment. Lancaster, PA: Technomic Publishing Company, Inc. 108-113. Worshop, R. L. (1994, February 11). Water quality: should safety standards for drinking water be tougher in the US? CQ Researcher, 4, (6).