POOL FACILITIES
Basic overview of UV technology
254nm is the sterilizing wave length UV light sterilizes the DNA string
185nm is the oxidizing wave length
Why does your pool need UV?
• Chlorine resistant parasites such as Cryptosporidium
• Destruction of chloramines in indoor facilities
• Monochloramine Dichloramine Trichloramine
Chlorine Disinfection of Recreational Water for
Cryptosporidium parvum
Colleen Carpenter,* Ronald Fayer,* James Trout,* and Michael J. Beach†
The small size of the Cryptosporidium parvum oocyst (4-6 um) and its resistance to many chemical disinfectants (e.g., chlorine) pose a challenge for standard filtration and disinfection procedures (1).
Moreover, the low dose required for infection and the prolonged excretion of high numbers of oocysts make C. parvum ideal for waterborne transmission. Chlorinated recreational water facilities, such as public swimming pools and water parks frequently used by large numbers of diapered children, have been implicated in numerous outbreaks of cryptosporidiosis during the last decade.
Destruction of Chloramines in indoor applications
Monochloramine Dichloramine Trichloramine
Monochloramines (NH2Cl) are formed when ammonia (NH3) combines with hypochlorous acid (HOCl). This process continues to the formation of Trichloramines (NCl3) which is what swimmers breath and smell near the surface of the water. These cause burning of the eyes and irritation of the mucous membrane.
UV destroys these chloramines
Duke University/University of North Carolina Study
"Impact of Chlorine and Monochloramine on Ultraviolet Light Disinfection"
"The absorption maximum of free-chlorine is somewhere around 290 nm which fallsin the range of polychromatic UV light from medium-pressure UV lamp output.
The absorption maximum of monochloramine is approximately 246 nm, close to the low-pressure UV lamp output at 254 nm. Therefore, when decay rates are based on delivered UV energy, monochromatic UV (254 nm irradiation) proves more effective
than polychromatic UV light in the photochemical degradation of monochloramine."
"Monochromatic UV light is more effective in degrading monochloramine, and polychromatic UV light is more effective in degrading Free-Chlorine".
- Duke University/University of North Carolina
DESTRUCTION OF DBP IN RECREATIONAL WATER APPLICATIONS
Germicidal UV (Low pressure) has the potential to reduce up to 85% of NCl3 (trichloramines) in recreational water facilities.
"Results indicate that NCL3 and CH3NCL2 can be degraded by up to 85% under UV irradiation, and the dynamics depend on the wavelength of UV irradiation.
Study by School of Civil Engineering, Purdue University
Free chlorine changes relatively slowly as a result of UV exposure. The results of these experiments suggest that germicidal UV radiation has the potential to reduce the concentration of some volatile DPB’s in swimming pools"
SUMMARY
• We have established that UV is an essential component to ensure safe pool water
• We have established that cryptosporidium is sterilized by UV
• We have established that chloramines are reduced significantly by UV
• We have established that Polychromatic light (Medium Pressure UV) has a negative effect on free
chlorine where monochromatic light (low pressure UV ) has a negative effect on monochloramines.
