Frequently Asked Questions

1. Q: What is ultraviolet disinfection?
  A: Ultraviolet light is radiation that lies between the X-ray region and visible region on the electromagnetic spectrum. UV ranges from 200 nanometers (nm) to 390 nm. Optimally, germicidal action occurs at 260 nm.

UV is produced through the conversion of electrical energy in a low-pressure mercury vapor quartz lamp. Electrons flow through the ionized mercury vapor between the electrodes of the lamp, which then create UV light.

UV disinfection can kill or render harmless microorganisms such as bacteria, viruses, algae and protozoa. The process consists of the UV light breaking through the cell wall and cytoplasmic membrane, rearranging the DNA and rendering the microorganism harmless.

Proper pretreatment must be used to effectively destroy microorganisms to a 99.9 % kill rate. UV does not leave any residuals, so it should be located as close as possible to the final distribution system. Any water treatment device installed downstream of the UV system could recontaminate the water. UV systems, alone, do nothing to reduce organic or inorganic contaminants in your water. Used alone, UV radiation does not improve the taste, odor, or clarity of water.

2. Q: What are the advantages of UV?
  A: Some of the advantages of using ultraviolet include:

- It effectively destroys microorganisms such as bacteria, algae, protozoa and viruses;
- Does not require chemicals, so it does not produce byproducts;
- It's readily available;
- Equipment is relatively easy to operate and maintain;
- It has short contact times;
- Can eliminate chlorine / chloramines and associated byproducts;
- In air treatment, can destroy mold spores;
- Does not affect the taste or mineral content of the water;
- It does not waste water.

3. Q: What are the disadvantages?
  A: Some limitations of using ultraviolet include
- Reduced performance in water with high levels of iron or color; and
- Requires pretreatment with a sediment filter (5-micron nominal).

4. Q: Which factors may affect UVs performance?
  A: Installation of the required sediment prefiltration (5-micron nominal) will eliminate the possibility for certain water quality factors, such as turbidity and suspended solids, to affect the performance of a UV system.

There are other water quality factors not taken care of by the standard, required prefiltration. Specifically, iron and hardness should be considered and pretreatment for these parameters may be required if levels exceed those specified by the UV manufacturer.

In addition, the location of UV could affect system performance. The UV system should be the last water treatment device before point of use because other devices may cause recontamination.

5. Q: What are some common UV applications?
  A: Common applications include:
- Well water;
- Bottled water plants;
- Hospitals;
- Restaurants;
- Water vending;
- Air Treatment;
- Laboratories;
- Boiler feed water;
- Spas;
- Wineries;
- Dairies;
- Cooling towers;
- Food processing;
- Schools;
- Farms;
- Boats;
- RVs;
- Pre- and post-RO treatment;
- Electronics;
- Groundwater;
- Surface water;
- Pharmaceuticals;
- Breweries;
- Textiles;
- Canneries;
- Cosmetics manufacturing;
- Airplanes;
- Trailer parks;
- Waste water plants;
- Swimming pools;
- Beverage manufacturing;
- Pond and lake reclamation;
- Dialysis;
- Aquariums and hatcheries;
- Hotels; and
- Cisterns.

6. Q: What is advanced oxidation?
  A: One of several processes making use of two or more treatment processes used conjointly for the specific purpose of oxidizing and destroying chemical constituents in the water. A common form of advanced oxidation makes use of UV in combination with hydrogen peroxide. UV may also be applied in conjunction with ozone. This process accelerates the decomposition of ozone, yielding a sufficient quantity of hydroxyl radicals to affect water purification and lower disinfection byproducts. Advanced oxidation can be a combination of:

- Ultraviolet and hydrogen peroxide;- Ultraviolet and ozone;- Ozone and hydrogen peroxide; and/or
- Ozone and elevated pH.

7. Q: What is the NSF/ANSI Standard 55?
  A: NSF/ANSI Standard 55 refers to ultraviolet microbiological water treatment systems. It is the industry's "stamp of approval." Products certified under this standard have passed a stringent process that evaluates the product's structural integrity, material evaluation, contaminant reduction claims and a review of its literature.

The standard covers POU and POE ultraviolet systems and includes two optional classifications: Class A and Class B.

• Class A systems are designed to disinfect and/or remove microorganisms from contaminated water to a safe level; and
• Class B systems are designed for supplemental bactericidal treatment of public drinking water or other drinking water that was deemed acceptable by a health agency.

As an alternative to testing NSF, the Water Quality Association also provides its testing services through its Gold Seal Program. The Gold Seal certifies to the same standards as NSF. WQA only awards the Gold Seal to those systems, components, or additives that have met or exceeded industry standards for contaminant reduction, structural integrity and material safety.

In addition, ultraviolet light is recognized by the Centers for Disease Control for its ability to effectively destroy germs and other biological pollutants.

8. Q: How is ultraviolet strength measured?
  A: UV light is measured in water treatment as millijoules per centimeter squared (mJ/cm2). The U.S. Department of Health states that a UV system should provide a minimum of 16 mJ/cm2, however an increasing number of jurisdictions require a dose of 40 mJ/cm2.

9. Q: What is a quartz sleeve?
  A: A quartz sleeve or jacket is a clear, pure fused quartz tube used to protect the high intensity UV lamps in UV purifier systems. It usually retards less than 10 % UV radiation loss. The sleeve restricts the lamp from coming into contact with the water to ensure lamp temperature remains consistent, electrical contacts are not shorted out and to allow maximum transmission of UV to the water. Maintenance required is simply wiping down the sleeve with a damp cloth.

10. Q: Which other treatment devices is UV often combined with?
  A: UV disinfection treatment is most effective when combined with:
- Sediment filters (required);
- Carbon filters (if required); and
- Water softeners.

Sources: 1. IUVA.org. 2003. 2. National Drinking Water Clearinghouse. Tech Brief One, June 1996. 3. Triangular Waves Technology, Inc. 4. McGowen, Wes. All About Water, Scranton Gillette Communications, 2000. 5. NSF International. Drinking Water Treatment Units: A Certification Guide. 6. www.wqa.org. The Water Quality Association, 2003.