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Frequently Asked Questions About Ultraviolet Purification

If you use water that comes from a municipal water supply and wish to provide your family with an added "peace of mind", then a UV system acts as an inexpensive insurance policy against the possibility of drinking bacteriologically contaminated water.

1. What is UV?
Ultraviolet (UV) light is at the invisible, violet end of the light spectrum. Even though we can't see UV light, we are exposed to UV rays from all light sources, including the sun.

2. Why do I need to disinfect my water supply woth a UV?
Unfortunately, due to the uncertainties that exist with our current water supplies, we can no longer rely on the fact that our water supplies 'may be safe'. By providing your own disinfection, you are taking the responsibility of ensuring the safety of your water supply for you and your family.

3. Why not use chlorine instead?
Chlorine changes the tastes and odor of water. Chlorinating also produces harmful by-products called Trihalomethanes (THMs) which are linked to incidence of cancer.

4. Does a UV system use a lot of energy?
No, the UV unit will use about the same amount of energy as a 60 watt light bulb. It is a cost effective, natural way to increase water quality.

5. Why do UV purifiers require sediment pre-filtration?
UV systems require pre-filtration to maintain effectiveness as sediment and other contaminants in the water can create a "shadow" which prevents the UV rays from reaching and disinfecting the harmful microorganisms.

6. How often does the UV light bulb (lamp) need to be replaced?
It is essential that you change your UV lamp annually. The ability of the lamp to emit UV light decreases over one year in operation. Remember - UV light is invisible! Even though the lamp is still glowing after one year, there might not be enough UV light reaching your water to be effective.

7. How often do your need to replace the sleeve?
The sleeve doesn't need to be replaced unless it is broken, but it will need to be cleaned several times a year in order to keep the bulb effective in delivering high water quality.

8. How does the UV light actually kill microorganisms?
UV does not kill microorganisms like chlorine does, but instead UV inactivates them. UV light at a specific wavelength of 254 nm is readily absorbed by the genetic material of microorganisms. The DNA strand is coded with a specific sequence of something called base pairs. The sequence of these base pairs codes for certain characteristics. UV light at 254 nm is readily absorbed at the point on the microorganism's DNA strand which codes for reproduction. A microorganism that cannot reproduce, cannot make colonies and therefore cannot infect when consumed. In other words, the microorganisms have been sterilized or neutered. They will eventually die off.

The picture on the left shows a DNA strand of a microorganism. You can see where the UV light is absorbed and how a blockage is formed, causing the microorganism to become sterile.

9. Does UV inactivate Cryptosporidium (Beaver fever) and Giardia?
Cryptosporidium and Giardia are what is called a protozoan cyst. Protozoa can be described as microscopic, single celled microorganisms which live in water and are quite a bit larger in comparison to other microbes. The majority of protozoan cysts are parasitic. Both Cryptosporidium and Giardia are parasitic. These organisms are in a dormant phase when in water but when they enter a host (being any kind of mammal) they release colonies and begin to breed, ultimately causing severe diarrhea and dehydration over a prolonged period of time.

Cryptosporidium and Giardia were not microorganisms of concern until approximately 10 years ago when Milwaukee was hit with a waterborne disease epidemic. Milwaukee drinking water is surface water, which had become contaminated with high concentrations of Cryptosporidium at the time. Over 100,000 people came down with Cryptosporidiosis and over 400 people died. The USEPA recognized that they needed to consider these organisms and include them within their drinking water guidelines. Testing was done and it was found that chlorine was NOT effective against either of the protozoa. Testing was then conducted using UV technology with initial failure due to improper test procedures. Ultimately it was proven that UV is in fact very effective against Cryptosporidium and Giardia. The dose levels required to inactivate these cysts are actually quite low; less than 10 mJ/cm² for 99.9% reduction of both Cryptosporidium parvum and Giardia lamblia.

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