Ultraviolet Water Purification

Did you know Ultraviolet (UV) systems can destroy 99.99% of harmful microorganisms without adding chemicals or changing your water’s taste or odor? It is one of the four methods of disinfection approved by the United States FDA. UV has proven to be a quick, reliable and cost effective method of disinfecting water for both point of use and point of entry.

UV is a safe, clean, easy-to-maintain method of assuring that water is free of bacteria. UV Water Purification uses Ultraviolet light, just like sunlight, to kill micro-organisms that may be in the water. It is a proven technology that has no significant drawbacks. In some applications, its initial cost is a bit more than chlorination, but because of its low operating cost, it quickly pays for itself. It is environmentally friendly and essentially trouble-free. Most ultraviolet water treatment systems require only an annual change of lamp – as simple as changing a light bulb – and a periodic change of the filter cartridge.

About UV Water Purification

There are over 19 million American households and cottages that rely on private wells. Tens of thousands more rely on lakes, streams and other surface water sources. Unfortunately, not all of them have a UV water purification system protecting them from harmful microorganisms.

While a nation-wide study does not exist, smaller scale studies have commonly found that 40% of wells in any given region suffer from E. Coli and/or coliform bacteria at any given time not to mention the countless other microorganisms that may be in a water supply.

The quality of well water can vary from day to day and from year to year in the short term, things like heavy rainfalls or snow melt can affect water quality. In the long term quality may be affected by distant contamination sources such as earthquakes, and other factors. Water that has been safe for years will not necessarily be safe tomorrow.

What is Ultraviolet (UV)

Ultraviolet or “UV” is a type of energy found in the electromagnetic spectrum, lying between x-rays and visible light. Although we cannot see UV light or rays, we are exposed to them every time we step out into the sun. In fact, UV light is responsible for causing sunburns. Ultraviolet systems use special lamps or bulbs that emit UV light of a particular wavelength. The Ultraviolet energy attacks the genetic core of the microorganism and rearranges the DNA /RNA eliminating the microorganism's ability to function and reproduce. If the microorganism can no longer reproduce, it cannot replicate, therefore it cannot infect other organisms with which has contact. The process is simple but effective, destroying 99.99 percent of harmful microorganisms without adding chemicals to the water.

The quality or appropriateness of both the UV light and of the 'contact ', are crucial to accomplish disinfection. It is important to properly 'size' the UV based upon the application. It is equally important to use a good pre-filter to remove any dirt or debris that may be present in the raw water supply. This dirt and debris can interfere with the effectiveness of the UV rays – virtually giving the microorganism a shield to protect them when passing the UV rays. The keyword here is quality.  System manufacturers strongly recommend that any pre and post filters be replaced at specified periods and that the UV lamp be replaced on an annual basis or after 9,000 hours of use -- whichever comes first.

Advantages of UV

There are some very important reasons why both homeowners and municipalities are choosing UV technology to treat their water.

  • Highly effective: For over 25 years, UV technology has been trusted as a safe, cost-effective way to purify water and eliminate harmful microorganisms. It is a proven EPA endorsed technology that is currently being used by thousands of cities, bottled water manufacturers and homeowners around the world.
  • Chemical free: UV provides water purification without the addition of harmful chemicals such as chlorine. It also avoids the potential of generating harmful chemical disinfection by products. Recent EPA guidelines are forcing cities across the United States to reduce or eliminate the use of chlorine for exactly this reason.
  • Taste & odor free: UV does not change the taste, odor or color of the water.
  • More effective than chlorine: Unlike chlorine, UV systems are effective against both Cryptosporidium and Giardia.
  • Compact and easy to maintain: UV systems are capable of treating a single faucet or an entire home in a minimal amount of space with the only maintenance being an annual lamp and filter replacements.

Water Quality

Successful disinfection depends upon exposing water to a sufficient intensity of UV light for a sufficient amount of time. Water failing to meet certain general water quality guidelines may reduce the effectiveness of a system.

For a UV system to work effectively the water must be pre-filtered to exclude any particles larger than 5 microns (nominal) in size. This pre-filtration assures that particles large enough to block the UV light do not pass through the system. If they do the particles can act as a shield between the microorganism and the UV light – protecting the microorganism and allowing it to pass into the product water unharmed and alive.

Common Questions about Ultraviolet Systems

What is Ultraviolet (UV)?
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 Germicidal Spectrum or Frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). The UV lamps that we use are designed specifically to have the highest amount of UV energy at this frequency.

How is Ultraviolet strength measured?
The UV light, 254 nm, is measured in water treatment as Microwatts per Centimeter square. The United States Department of Health has determined that an effective UV system should provide a minimum of 16,000 Microwatts per Centimeter Square.

Is the UV light exposed directly to the water?
Yes and No. Yes, the rays are exposed, no the bulb is not. The UV light is in the center of the filter, surrounded by a clear quartz sleeve. The bulb is protected by this sleeve. The sleeve is exposed directly to the water. The best way to penetrate water with the UV light is to expose outward radiants into the water and the UV rays penetrate the water to kill microorganisms.

What is the Quartz Sleeve?
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 104 Degrees Fahrenheit.
  3. To allow maximum transmission of the UV energy into the water. The Quartz Sleeve is made of pure-fused Quartz which has a transmission rate of approximately 98 percent.

How is the quartz sleeve cleaned and how often should it be cleaned?
The quartz sleeve should be wiped down with a damp cloth each time the lamp is changed. On some models the Quartz Sleeve can be cleaned without being removed from the UV system. In some cases the sleeve cannot be cleaned but should be discarded and replaced.

How often should the UV lamp be changed?
The UV light is designed to operate for (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 micro-organisms.

Does UV purification make the water taste better?
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 this oxidation. This oxidation only takes place when the water is standing for a long period of time in front of the UV lamp.

Should UV be used with other forms of filtration?
Yes, Because UV does not change the quality of the water other than killing the bacteria and virus, it is always recommended that Sediment pre-filter and Carbon post-filter are used with a UV lamp. This configuration makes a complete UV System.

Why is it necessary to use a 1 micron filter with my UV system?
The outer layer or shell of a cyst is extremely difficult to penetrate with a UV light. Because of the, UV manufacturers recommend that a 1 micron (absolute) filter be included in the UV System.

When used with other filters, where should the UV be placed?
The UV lamp should always be preceeded with a prefilter and followed with a carbon filter. It is always recommended that the Ultraviolet system itself be the last water treatment device before the point-of-use. Any filter or other water treatment devices may cause re-contamination.

What causes black particles to appear in the water when using a carbon filter with UV?
The black particles that appear in the water are from the carbon filters used with the UV light. When the carbon filters are first put into use a small amount of carbon particles may appear in the water. These particles are harmless and are flushed out during the initial use of the filter.

Is ultraviolet as harmful as radiation?
No. The UV light only penetrates the water and is very much like sunlight. There is no residue or residual of any kind in water that has been treated with the Ultraviolet light. It is important to always use caution when servicing a UV system so you are not exposed directly to the UV light.

How much water pressure is required to operate most UV systems?
Most UV systems are designed to operate ideally at approximately 65 psi (pounds of pressure per square inch). Although many systems may operate with pressures as low as 20 psi, the flow rate will greatly decrease due to the low water pressure. It is always recommended that if the pressure exceeds 75 psi a pressure reducing valve should be used.

Can I run hot water through my UV system?
It is not recommended to run hot water or water greater than 100 Degrees Fahrenheit through the UV system. At higher temperatures plastics and rubber may soften, distort or weaken causing the system to fail.

If the UV lamp is darkened, is it defective or not working properly?
No. Darkening at the end of the UV lamp is normal. The UV lamps rarely fail, and when they do it is usually caused by voltage that is to high or to low. It is extremely important that the UV lamp be replaced on an annual basis.

What is the difference between hard and soft glass UV lamps?
Hard glass is pure-fused Quartz and maintains its ability to transmit UV light over a longer period of time than soft glass. Soft glass lamps use a glass more like normal window glass. The UV light causes this glass to solarize and inhibits the transmission of UV light. Normally soft glass has a life span of 90 days, where hard glass lamps are designed to operate for at least one (1) year.

If I turn the UV lamp off while it is not in use, will it last longer?
No, It is not recommended to turn the UV light on and off unless the system has been specifically designed to do so. The on and off cycling of a UV lamp that is designed to be left on at all times can cause premature lamp failure. On average the lamp can loose as much as six (6) hours of lamp life each time it is turned on and off.

Can I use filters other then the ones provided with the system?
It is recommended that you not use filters other than those whos specifications match the specifications of the filters that came with the system. Filters that do not meet these specifications will reduce the effectiveness of the system.

How long should the filter(s) last?
Filters should normally last six – twelve (6-12) months depending on the quality of the water. In areas where the water has a high amount of sediment, it is recommended that you use a double or triple system, which has a Sediment (SD) filter before the carbon filter (s). ESP does offer a larger sized filter that will last longer under heavy sediment conditions.

Can I use UV for the whole house at the point of entry?
Yes, A UV system can be used to treat the entire house. There are several UV systems designed specifically for this application. It is very important the lines in the house be cleaned before using the UV system. If the lines are dirty, the water will re-contaminate after the UV system is installed. It is easiest to sterilize the lines by introducing a chlorine solution and letting it stand for a period of time.

Why does the flow rate reduce with the use of Sediment and Granular Activated Carbon (GAC) Filters?
The Pre & Post Filters will create a resistance or back-pressure on the incoming water flow reducing the flow rate of the water.

Do ordinary filters kill bacteria?
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 light should always be the last pass after the filters to ensure that bacteria does not pass through to the drinking water.

Do Carbon filters breed bacteria?
Bacteria can survive within a Carbon filter, but this is normally not a problem if the filter is in continuous use. If the filter stands for a long period of time, bacteria can multiply.

What does "Bacteriostatic" mean?
The term "Bacteriostatic" means the quantity of bacteria passing through the system will be static – bacteria will not multiply. For example: if you have a count of 100 colony forming units going into the filter you will have 100 colony forming units coming out. Bacteriostatic filters do not kill bacteria, but only inhibit the growth of bacteria within the filter.