Academic journal article Journal of Environmental Engineering and Science

Pulsed UV Lamp Performance and Comparison with UV Mercury Lamps (1)

Academic journal article Journal of Environmental Engineering and Science

Pulsed UV Lamp Performance and Comparison with UV Mercury Lamps (1)

Article excerpt

Abstract: Pulsed lamps based on electric discharges in xenon are of interest for water treatment because they are free of mercury, have instant-on capability, and may provide enhanced effects due to the high irradiance of pulses or spectral differences. This study provides quantitative comparisons of standard mercury UV lamps with both a commercial flashlamp and a pulsed surface discharge lamp. Unlike mercury lamps, the UV performance of pulsed lamps is a function of operating parameters. In this study the measured UV efficiency of a flashlamp, with a specified practical lifetime, increased as the pulse length decreased, from 4.4% at 796 [micro]s to 9.0% at 71 [micro]s. The surface discharge lamp, which overcomes limitations of flashlamps, had a measured UV efficiency of 17% at 12 [micro]s. In comparison, standard commercial low pressure and medium pressure mercury lamps evaluated in this study had UV efficiencies of 34.6% and 12.2%, respectively.

Key words: pulsed UV, water treatment, flashlamp, surface discharge, mercury.

Resume : Les lampes a impulsions basees sur les decharges electriques dans le xenon sont interessantes pour le traitement de l'eau puisqu'elles ne contiennent pas de mercure; elles possedent la capacite d'etre mises en marche instantanement et elles peuvent avoir des effets accrus en raison de la haute irradiance des impulsions ou des differences spectrales. La presente etude compare quantitativement les lampes standards UV a la vapeur de mercure avec des lampes-eclairs commerciales et une lampe a decharge superficielle a impulsions. Contrairement aux lampes a vapeur de mercure, le rendement UV des lampes a impulsions est fonction des parametres de fonctionnement. Dans cette etude, l'efficacite mesuree d'une lampe-eclair UV, ayant une duree de vie utile specifiee, augmentait a mesure que diminuait la longueur de l'impulsion, de 4,4 % a 796 [micron]s a 9,0 % a 71 [micron]s. La lampe a decharge superficielle, qui comble les limites des lampeseclairs, presentait une efficacite UV mesuree de 17 % a 12 [micron]s. En comparaison, les lampes commerciales standards a faible et a moyenne pression de vapeur de mercure evaluees lors de cette etude presentaient respectivement des efficacites UV de 34,6 % et de 12,2 %.

Mots-cles : UV a impulsions, traitement de l'eau, lampe-eclair, decharge superficielle, mercure.

[Traduit par la Redaction]

Introduction

Ultraviolet light is a proven means for disinfection and remediation of water, as well as many other applications. UV is used widely in Europe for water disinfection and its use is becoming more widespread in the US with EPA acceptance of UV disinfection of drinking water, as indicated by two 2006 regulations, the Stage 2 Disinfection Byproducts (DBP's) Rule (EPA 2006a) and the Long Term 2 (LT2) Enhanced Surface Water Treatment Rule (EPA 2006b). UV may be preferable over more traditional chemical disinfectants because of their tendency to produce disinfection by-products of regulatory concern. Furthermore, UV has been shown to be highly effective in the inactivation of difficult to treat protozoan pathogens of health concern, such as Giardia lampda and Cryptosporidium parvum (Linden and Mofidi 2003).

Mercury lamps are the standard for most UV commercial applications. However, environmental and health concerns from potential mercury contamination due to lamp failure, lamp disposal, and the necessary warm-up time of mercury lamps (where quick response is an issue, such as in Homeland Security applications) has led to interest in pursuing the efficacy of alternative non-mercury based lamp technologies.

Pulsed xenon flashlamp technology is mercury free, has instant-on capability, and has received attention for a wide range of disinfection and remediation applications (Liang et al. 2003; Mofidi et al. 2001; Wekhof 2003; Weber and Scheible 2003; MacGregor et al. 1998; Rowan et al. 1999; Krishnamurthy et al. …

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