254 Nm Ultraviolet Lamp for Water Sterilizer

The UV Alternative
An increasingly popular dechlorination technology, with none of the above drawbacks, is ultraviolet (UV) treatment. High intensity, broad-spectrum UV systems (also known as medium pressure UV) reduce both free chlorine and combined chlorine compounds (chloramines) into easily removed by-products.
Between the wavelengths 180 nm to 400 nm UV light produces photochemical reactions which dissociate free chlorine to form hydrochloric acid. The peak wavelengths for dissociation of free chlorine range from 180 nm to 200 nm, while the peak wavelengths for dissociation of chloramines (mono-, di-, and tri-chloramine) range from 245 nm to 365 nm. Figure 1 shows the UV output of a high intensity Hanovia medium pressure UV lamp. Up to 5ppm of chloramines can be successfully destroyed in a single pass through a UV reactor and up to 15ppm of free chlorine can be removed.
Many water treatment systems include RO units, which commonly use thin-film composite membranes because of their greater efficiency. However, these membranes cannot tolerate much chlorine, so locating the UV unit upstream of the RO can effectively dechlorinate the water, eliminating or greatly reducing the need for neutralizing chemicals or GAC filters.
The UV dosage required for dechlorination depends on total chlorine level, ratio of free vs. combined chlorine, background level of organics and target reduction concentrations. The usual dose for removal of free chlorine is 15 to 30 times higher than the normal disinfection dose. Membranes therefore stay cleaner much longer because the dose for dechlorination is so much higher than the normal dose used if dechlorination was not the goal. Additional important benefits of using UV dechlorination are:
 High levels of UV disinfection
 TOC destruction
 Eliminate safety hazard associated with mixing bisulphate
 Eliminate risk of introducing micro-organisms into RO (via GAC or injection of neutralizing chemicals)
 Overall improved water quality at point-of-use
As with other dechlorination technologies, the UV dosage required at a given flow rate is dependent on several process parameters, including:
 Process water transmittance level
 Background organics level
 Influent chlorine level and target effluent chlorine concentration level