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Aging of Low Pressure Amalgam Lamps on UV Dose Delivery

Aging of Low Pressure Amalgam Lamps on UV Dose Delivery

Schmalwieser, Alois, Harold Wright, Alexander Cabaj, Mark Heath, Erin Mackey, Gunther Schauberger
Published In: 
Journal of Environmental Engineering and Science ,  
April 2014
​To provide a more cost-effective UV disinfection, amalgam low-pressure high-output UV lamps (ALPHO lamps) were proposed as an alternative to low- and medium-pressure lamps in the 1970s. ALPHO lamps use an amalgam of mercury and other metals such as bismuth, indium, lead and tin, attached to the inside wall of the lamp's quartz envelope, to regulate the mercury vapor pressure within the lamp to optimal values. The regulation of mercury vapor pressure allows the lamps to operate at higher input power densities while maintaining relatively high electrical-to-germicidal energy conversion efficiently. An important issue with all UV lamps is lamp aging, which impacts lamp life and UV output over time. UV systems are typically sized to deliver the required UV dose with the lamp output expected at the end of lamp life. Typically, the lamp output from the lamp is assumed to be uniform over the length and around the circumference of the lamp. However, visual observations of aged lamps show non-uniform lamp aging. Non-uniform aging for UV lamps potentially impacts UV dose delivery and it may also impact UV dose monitoring. There are only a few published studies on the impact of lamp aging on UV output and none of them address the impacts of non-uniform lamp aging. This paper presents measurements of the spatial distribution of spectral irradiance from ALPHO lamps used in water disinfection as a function of operating time.
Schmalwieser, A., H. Wright, A. Cabaj, M. Heath, E. Mackey, and G. Schauberger," Aging of Low Pressure Amalgam Lamps on UV Dose Delivery." Journal of Environmental Engineering and Science, Volume 9, Issue JS2, pp: 113-124.