Operation and Maintenance of UV System in Aqueous Environments

UV lamp is the most crihcal element in the disinfection. The most widely used UV lamps can be classihedinto low-pressure low-intensity lamp, low-pressure high-intensity lamp, medium-pressure high-intensity lamp, high-pressure high-density lamp, and other types of lamps. The details of the typical lamps are listed in Table 3. The low-pressure mercury lamp works in an internal pressure range of 0.001-0.1 torr. Mercury is typically 

Items Low-pressure low-output lamp Low-pressure high-output lamp Medium-pressure high-output lamp  

Advantages Higher germicidal efficiency, nearly all ontput at 254 nm smaller power draw per lamps Longer lamp life Higher power output fewer lamps for a given application smaller reactors 

Disadvantages More lamps needed Higher operating temperature can accelerate fouling shorter lamp life lower electrical to germicidal conversion efficiency 

UV lamps are housed within the lamp sleeves. Quartz is often used to build lamp sleeves with open ends. The sleeve is used to protect, cool, and insulate the UV lamps. The most commonly used lamps in water and wastewater disinfection are low-pressure low-intensity mercury vapor lamps [also termed low-pressure low-output (LPLO) mercury vapor lamps], low-pressure high-intensity mercury vapor lamps (also termed as LPHO mercury vapor lamps), and medium-pressure mercury vapor lamps. Other lamps include electrode-less mercury vapor lamps, metal halide lamps, xenon lamps (pulsed UV), and eximer lamps. UV lamps may be oriented parallel, perpendicular, or diagonal to flow or ground. Orienting MP lamps horizontally relative to the ground prevents differential heating of the lamps and reduces the potential for lamp breakage. 

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