The ultraviolet rays from the sun have long since been known for their ability to destroy micro-organisms. However, it has only been in recent years that ultraviolet equipment has been manufactured for the home consumer.
Ultraviolet, commonly referred to as UV, is an extremely efficient form of disinfection. For residential use, it is an excellent system because of it's reliability and ease of maintenance.
The UV lamp is similar to a fluorescent lamp in appearance only. It operates by arcing electricity through a low pressure mercury vapor producing light waves at 254 nm (2537 Å) UV energy necessary to sterilize the water born micro-organisms. In order to achieve its full intensity, the UV lamp needs two (2) minute start up periods. Therefore, it is recommended to leave the system in operation at all times. After each start up period, a six (6) hour lamp loss is The lamp that is now in your system needs to be replaced every twelve (12) months to ensure proper disinfection of the water.
In order to allow the lamp to maintain its ideal operating temperature, 104o Fahrenheit, an additional hard quartz sleeve is used to isolate the lamp from the cooler water. It is very important the sleeve is kept clean so the maximum dosage of UV energy is allowed to pass into the water. It is recommended to clean the sleeve every three (3) months with soap and water.
Five (5) major groups of micro-organisms are destroyed with the Ultraviolet process. Organisms sterilized are viruses, bacteria, fungi spores algae, and Protozoa. Exposure to the UV energy, causes the microbe's DNA (deoxyribonucleic acid) to "scramble," prohibiting reproduction. Sterile cells cannot reproduce, therefore it is considered "dead" and no longer a threat.
The United States Department of Health has established that proper exposure should be a minimum of 16,000 micro watts per centimeter square to achieve potable water standards.
The filter system that PURA has incorporated into the unit serves a dual purpose. Its first task is to remove the suspended solids from the water because they provide an excellent shield for the microbes to hide behind; therefore, making it difficult to receive sufficient UV exposure. Second, because PURA uses carbon filtration, we are also removing unpleasant tastes and odors; assuring the consumer of safe, good tasting water.
ULTRAVIOLET ENERGY LEVELS AT 254 NANOMETER UNITS WAVELENGTH REQUIRED FOR 99.9% DESTRUCTION OF VARIOUS MICRO-ORGANISMS UV Energy in Microwatt-Seconds per Centimeter Square
BACTERIA MOLD SPORES Agrobacterium Tumefacient 8500 Aspergillus Flavum 99000 Bacillus Anthraces 8700 (yellowish green) Bacillus Megaterium (vegetative) 2500 Aspergillus Glaucus 88000 Bacillus Megaterium (spores) 52000 (bluish green) Bacillus Subtilin (vegetative) 11000 Aspergillus Niger (black) 330000 Bacillus Subtilin (spores) 58000 Mucor Ramosissimus (white gray) 35200 Clostridium Tetany 22000 Penicillium Digitatum (olive) 88000 Corynebacterium Diphtheria 6500 Penicillium Expensum (olive) 22000 Escherichia Coli 7000 Penicillium Roqueforti (green) 26400 Legionella Bozemanii 3500 Rhizopus Nigricans (black) 220000 Legionella Dumoffii 5500 Legionella Gormanii 4900 Legionella Micdadei 3100 ALGAE Legionella Longbeachae 2900 Legionella Pneumophila 3800 (Legionnaires Disease) Chlorella Vulgaris (algae) 22000 Leptospira Interrogans 6000 (Infectious Jaundice) Mycobacterim Tuberculosis 10000 PROTOZOA Neisseria Catarrhalis 8500 Proteus Vulgaris 6600 Pseudomonas Aeruginosa 3900 Nematode Eggs 92000 (laboratory strain) Paramecium 200000 Pseudomonas Aeruginosa 10500 (environmental strain) Rhodospirilium Rubrum 6200 VIRUSES Salmonella Enteritidis 7600 Salmonella Paratyphi 6100 (Enteric Fever) Bacteriophage (E. Coli.) 6600 Salmonella Typhimurium 15200 Hepatitis Virus 8000 Salmonella Typhosa 6000 Influenza Virus 6600 (Typhoid Fever) Poliovirus (Poliomyelitis) 21000 Sarcina Lutea 26400 Rotavirus 24000 Serratia Marcescens 6200 Tobacco Mosaic Virus 440000 Shigella Dysenteriae (Dysentery) 4200 Shigella Flexneri (Dysentery) 3400 Shigella Sonnei 7000 YEAST Staphylococcus Opidermidis 5800 Staphylococcus Aureus 7000 Streptococcus Faecalis 10000 Baker's Yeast 8800 Streptococcus Hemolyticus 5500 Brewer's Yeast 6600 Streptococcus Lactis 8800 Common Yeast Cake 13200 Viridans Streptococci 3800 Saccharomyces var. Ellipsoideus 13200 Vibrio Cholerae (Cholera) 6500 Saccharomyces sp. 17600 COMMON QUESTIONS ABOUT ULTRAVIOLET SYSTEMS Q. What is Ultraviolet? A. Sunlight has long since been known to kill micro-organisms. The rays from the sun contain the UV Spectrum used in Ultraviolet Water Treatment Systems -- although at much lower intensities. It is also referred to as either the Germicidal Spectrum or frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). The UV lamps that PURA uses are designed specifically to have the highest amount of UV energy at this frequency. Q. How is Ultraviolet strength measured? A. The UV light, 254 nm is measured in water treatment as microwatts per centimeter square. The United States Department of Health has determined that a UV system should provide a minimum of 16,000 microwatts per centimeter square. Q. Is the UV light exposed directly to the water? A. Yes. The UV light is in the center of the filter; therefore, is exposed directly to the water. The best way to penetrate water with the UV light is to expose outward radiants into the water. Q. What is the quartz sleeve? A. The quartz sleeve is made of pure - fused quartz which has a transmission rate of approximately 98 percent. The quartz sleeve serves three purposes: 1. To isolate the lamp from the water so the electrical contacts are not shorted out by the water; 2. To create a thermal barrier allowing the lamp to maintain its ideal operating temperature of 104o Fahrenheit; 3. To allow maximum transmission of the UV energy into the water. Q. How is a quartz sleeve cleaned? A. The quartz sleeve should be wiped down with a damp cloth each time the filter is changed. Removing the quartz sleeve is not necessary for cleaning. Scale or hard water deposits on the quartz sleeve can be removed by using a vinegar solution or a weak acid solution. Q. How long does a UV lamp operate? A. The UV lamps are designed to operate for one (1) year under continuous operation. The lamp will slowly lose energy during this period; therefore, the lamp should be changed annually to guarantee the amount of UV energy available is sufficient enough to kill any micro-organisms. Q. Does UV purification make the water taste better? A. No. The UV energy entering the water has no effect on the taste and odor of the water with the exception that certain chemicals will oxidize under the UV light. The taste may change due to oxidation. Oxidation only takes place when the water is standing for a long period of time in front of the UV lamp. Q. Should UV be used with other forms of filtration? A. Yes. Because UV does not change the quality of the water other than killing the bacteria. It is always recommended to have an additional carbon or sediment filter with a UV system. Q. When used with other filters, where should the UV be placed? A. It is always recommended that the UV system be the last water treatment device before point-of-use. Any filter or other water treatment device may cause re - contamination. Q. What causes the black particles to appear in the winter when using a carbon filter? A. The black particles that appear in the water are from the carbon filter. During transit, carbon filters generally give off small amounts of carbon particles. these particles will be flushed out during the initial use of the system. Q. Is Ultraviolet as harmful as radiation? A. No. The UV light only penetrates the water and is very much like sunlight. There is no residue or residual of any kind in the water that has been treated with the UV light. UV systems are designed so that no exposure to the UV light is possible. Always use caution when servicing a UV system so you are not exposed directly to the UV light. Q. How much water pressure is required to operate most UV systems? A. All PURA Systems are designed to operate ideally at approximately 65 pounds of pressure. Although many systems may operate with pressures as low as 20 pounds, the flow rate will decrease due to the low pressure. It is always recommended that if the pressure exceeds 75 pounds, a pressure reducing valve must be used. Q. May I run hot water through my system? A. It is not recommended to use hot water or water greater than 100o Fahrenheit through a UV system. At higher temperatures, the plastics may soften, distort, or weaken; therefore defecting the system. Q. If the UV lamp is darkened, is it defective? A. No. Darkening at the ends of the UV lamp is normal. The UV lamps rarely fail, and failure is usually caused by too low or too high voltage. It is extremely important that the lamp be changed each year. Q. What is the difference between hard and soft glass UV lamps? A. Hard glass is pure-fused quartz and maintains its ability to transmit UV light over a longer period of time. Soft glass lamps use a glass more like normal window glass, and the UV light causes this glass to solarize and inhibits the transmission of UV light. Normally, soft glass lamps do not last more than three (3) months. Hard glass lamps are designed to operate for a least one (1) year. Q. If I turn the UV lamp off while it is not in use, will it last longer? A. No. It is not recommended to turn the UV light on and off unless the system has been specifically designed for that. The on and off cycling on a UV lamp that is designed to be left on at all times can cause premature failure in the lamp. The lamp will also lose six (6) hours of lamp life each time it is turned off and on. Q. Why is Teflon used with the EPCB Filter? A. Teflon is used in the EPCB Filter to allow a double pass, or extended pass, of the water along the UV lamp. Very few materials are transparent to the UV light. Pure-fused Quartz and Teflon allow transmission of UV light. PURA has patented this application of the Teflon Sleeve within the filter. EPCB stand for Extended Pass Carbon Block. Q. Can I use non-PURA filters? A. Yes. As long as the filters meet PURA's high standard that can resist effects of UV light. However, PURA cannot guarantee the effectiveness of the system. The use of non-PURA filters will void any warranties on the system. Q. How long do filters last? A. Filters normally last up to six (6) months depending on the quality of the water. In areas where water has high amount of sediment, it is recommended that you use a double or triple system which has the sediment (SD) filter before the carbon filter (s). PURA also offers the carbon block filter in a ten (10) micron size that lasts longer under heavier sediment conditions. Q. Can I use an UV Unit for the entire house? A. Yes. UV units can be used for the entire house. The PURA UV20 Series is specially designed for this application. It is very important the lines in the house be cleaned before using the UV system. It is easiest to sterilize the lines by introducing a chlorine solution and letting it stand for a period of time. Q. Why does the flow rate reduce with the granular carbon (GC) filter? A. The GC filter does not have the extended pass Teflon Sleeve; therefore, the water only flows along the lamp in one direction reducing the amount of water that can be treated. The GC filter also has less carbon and contact surface for the filtration purpose. Its capacity and lifetime are also much shorter than the EPCB Filter. Q. Do ordinary filters kill bacteria? A. No. Ordinary filters cannot kill bacteria. The bacteria will enter the filter and either pass through the filter or grow within the filter. The UV unit is always the very last pass after the carbon filter to ensure that bacteria does not pass through to the drinking water. Q. Do carbon filters breed bacteria? A. Bacteria can survive within a carbon filter, but this normally is not a problem if the filter is used continuously. If the filter stands for a long period of time, bacteria can multiply. Q. What is Bacteriostatic? A. The term Bacteriostatic means the quantity of bacteria passing through the system will be static. In other words, not changing. For example: If you put 100 bacteria into the filter, you will get 100 out. The filters that are Bacteriostatic normally will have a silver content. Bacteriostatic filters do not kill bacteria, but only inhibit the growth of bacteria within the filter.
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