By Ron Hallett, P.E.

Selecting the right water purification solution to ensure your safety is one of the most critical decisions you’ll ever make. It involves more than just deciding who has the best list of system features and functions. To be absolutely certain of your water safety, the solution you choose must meet accepted industry standards.

Ultraviolet (UV) disinfection has only in recent years been recognized as one of the most effective, least complicated and least expensive technologies to use for effective water treatment. It’s gained supporters due to distinct advantages, i.e., no chemical by-products but powerful disinfection properties. Now, recent innovations in UV technologies and system design for rural residential, commercial and small community water treatment applications are dramatically improving UV water disinfection effectiveness and safety over conventional systems.

The advances in UV treatment that have emerged differ dramatically from conventional UV system design. By turning existing UV system design inside out, water is pumped inside the quartz tube for treatment instead of outside the tube. UV lamps are now mounted outside the quartz tube in the air. Shadowing is drastically reduced since the UV light enters the water chamber from 360 degrees.

Below is a list of things to look for when choosing your system:

New levels of UV efficacy—The technique of mounting the lamps outside the quartz tube has proven to be a very efficient use of UV light. Using two lamps in conjunction with elliptical reflectors provides a higher UV dose than is obtained with only one lamp. UV light is used far more effectively with this design since 95 percent of the UV light will reflect back into the quartz tube for a second or third time. A comparison of efficiencies between the two technologies shows more than double the UV dose for each watt of electrical power consumed.

New lamp location eliminates overheating—Having lamps mounted outside the quartz tube ensures lamp output isn’t dependent on water temperature. Lamps are cooled by natural convection, resulting in the water always being treated at the maximum UV dose from the first glass in the morning until the last one at night. Lamp changing becomes a quick two-minute task requiring only a screwdriver, and the system doesn’t have to be drained simply to change a bulb.

Eliminating quartz fouling—Automatic quartz cleaning devices have been introduced to minimize and, in most cases, eliminate quartz fouling. The unique advantages of passing the water inside the quartz tube make the automatic cleaning device both affordable and effective. By using a built-in mechanical device consisting of a simple central turning shaft and stainless steel wiping blades, the necessity for complicated reciprocating motion used in some conventional systems is eliminated.

Alarms and fail-safe shutoff—A pivotal innovation in UV system design includes the use of multiple sensors capable of monitoring both UV lamp output and water UV transmittance separately. UV sensors are also mounted in air to prevent fouling and the need for high-pressure housings. UV transmittance can be calculated with assistance of a microprocessor to compare sensor readings of one UV lamp out-put with output of the second lamp sensor readings as seen through the water and quartz tube.

Any UV system that’s used to protect people from drinking contaminated water must have a method to detect when the water isn’t being treated with sufficient UV dose. Preferably, the system should incorporate a normally closed electric solenoid valve that shuts off the water if a problem occurs with the UV system. A normally closed valve is one that closes on loss of power. This is called a “fail-safe” valve since its mode of failure is in the safe condition.

Safety first—The dramatic advancements in UV technology described here have made these systems some of the safest and most reliable in the world. They have been tested and certified so their dose and UV sensors meet NSF Standard 55A-Ultraviolet Microbiological Water Treatment Systems.1 In fact, 22 of 54 products listed under Standard 55 have passed the Class A requirements.

Conclusion
Today, UV is the only technology certifiable for microbiological water disinfection. One of the reasons is its effective output is verifiable (via sensors) in real time. Choosing the right system for you and your family is a critical decision. Don’t settle for less.

Reference

  1. Hallett 13, ANSI/NSF Standard 55–Disinfection Performance, Class A (Rated at 13.3 GPM), NSF International, Nov. 12, 2001.

About the author
Ron Hallett, founder of UV Pure Technologies Inc., of Toronto, Canada, is a professional engineer and holds a bachelor’s degree from the University of Waterloo, Canada, in mechanical engineering. He holds memberships in the American Society of Industrial Engineers, the Association of Professional Engineers in Ontario, the American Water Works Association and serves on the NSF-55 Task Force with NSF International, a global certification authority for drinking water safety systems. He can be reached at (416) 208-9884, (416) 208-5808 (fax), email: [email protected] or website: www.uvpure.com

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