Ray of light: we shine a light on UV--a new technology for controlling chloramines at your pool.

We all know the reasons why chlorine is used to clean a pool, and swimmers certainly notice its presence. But recently, it's catching on that pool operators can keep a clean community pool without the odor and irritation of chlorine. The use of industrial ultraviolet (UV) technology for controlling the problems of chlorine at indoor commercial pools is catching on.

Chlorine isn't really the enemy--it is chloramines found in the chemical. UV light energy proactively and continuously reduces chloramines in the water being filtered. It should be noted that chlorine will still be used as a disinfectant, but the UV will be relied upon to reduce the noxious chloramines. Chloramine levels are regulated by law and are responsible for the odor and irritation noticed at indoor pools.

Other ways of addressing high chloramine levels involve "shocking" the pool. This process involves evacuating the pool and adding 10 times the amount of chlorine to burn away the chloramines. Once this occurs, more chemicals are added to reduce chlorine concentrations. This process is typically done overnight when labor costs are at their highest. The air handlers typically provide 100 percent new makeup air during this process. Heating the air during the winter will add to the energy bill. Another approach involves a sys tem which regularly injects additional chemicals to address the chloramine levels.

UV in Other Industries

UV technology has been used for decades on numerous industrial and municipal applications. The food, beverage, semiconductor, pharmaceutical, aquaculture, petrochemical and municipal markets have relied upon UV to improve the water without adding chemicals. The role of UV has expanded in many areas as industry has attempted to reduced or eliminate chemical use.

UV helps produce ultra pure water to rinse computer chips during production; it is also used to improve taste and extend shelf life of products we eat and drink; meanwhile, cities use it to replace chemical disinfection in treated wastewater emptied into rivers.

There are dozens of other unique applications which rely on UV technology as well, including cleaning up groundwater at EPA superfund sites. UV energy disassociates the bonds of pollutants, reducing them to simpler, less toxic compounds. It is this characteristic which makes it beneficial in controlling chloramines.

It should be noted that UV can also reduce free, or "good" chlorine. The amount of energy to accomplish this is considerably higher than what is required for controlling chloramines.

There are two types of UV technology to choose from and one type has been shown to more effective at reducing free chlorine and less effective at reducing monochloramines.

How It Works

The most common industrial application for UV is disinfection. UV light is not perceptible to the human eye and is often divided into three areas--UVA, UVB and UVC. The area of energy most beneficial for industry is UVC. Within the UVC range, energy attacks the DNA/RNA of bacteria and viruses. It neutralizes and effectively kills, a very wide range of bacteria, viruses, yeast and mold.

Although chlorine can kill most things, cryptosporidium is one of several chlorine-resistant pathogens which are unfortunately becoming better known by the general public. In 1993 more than 400,000 people became ill and 100 died in Milwaukee, Wisc., due to a "crypto" outbreak in the municipal drinking water. This last summer more than 3,000 swimmers became ill at a waterpark in New York and more than 700 in Cincinnati, Ohio, due to crypto.

It is an intestinal parasite which can be life-threatening to infants, elderly and people with compromised immune systems. Typically, it takes about seven days for symptoms of cryptosporidiosis to appear, long after the initial exposure occurred. The illness often can last up to two weeks. A UV system will proactively and continuously disinfect better than 99.99 percent of crypto in the filtered water on a single pass.

UV Lamp Choices

There are primarily two types of industrial UV lamp technology, amalgam (high-output, low pressure) and medium pressure. The word "pressure" refers to the gas pressure within the lamp itself. While both type of lamps work, they are very different.

Amalgam lamps produce energy at one exact wavelength within the UVC range. Medium pressure produces UV energy at every wavelength within the UVC range--approximately 120 wavelengths. While both are successful at reducing chloramines, refer to the chart below for a full list of each lamp's advantages.

The comparative information in the chart is all documented by peer-reviewed scientific study and published in U.S. Environmental Protection Agency (EPA) reports. Purveyors of medium pressure UV have stated that only medium pressure UV provides all the wavelengths for mono, di and trichloramine destruction.

This implies that low amalgam UV is ineffective on chloramines. This fact is disputed--a Duke University study concluded that monochromatic [amalgam] UV is more effective reducing monochloramines and medium pressure is better at reducing free chlorine. This year, the Centers for Disease Control will be testing amalgam UV at an indoor pool to determine the levels of mono, di and trichloramines in the water and the air, and will settle the dispute in the industry.

UV Selection

When specifying UV equipment, almost every other industry specifies the UVC "dose" level, but the aquatics industry often specifies lamp type. It does not matter which type of lamp is used--what is important is that a prescribed level of UVC energy provided. Many industries often use a level of UVC energy, or dose, of 30mJ/[cm.sup.2] for disinfection. Chloramine control often uses 60mJ/[cm.sup.2] as a sufficient UV dose, and thus results in disinfection as a secondary benefit.

UV lamps slowly reduce their output over their lifespan, so the specified dose should be at the end of lamplife. A new lamp will actually provide approximately 40 percent higher dose and will slowly degrade. When the lamp is scheduled to be replaced it will be providing a dose of 60mJ/[cm.sup.2].

Selecting a properly sized UV system is done by identifying the flow rate through the filtration system. Once this is determined, a properly sized system can be selected. UV systems work only on the water exposed to light when it passes through the treatment chamber--there is no residual effect. In the one to two seconds the water is exposed to the UV energy, chloramines will be reduced and pathogens will be disinfected. The faster the pool's turnover rate, the more effective the system will be. Pools with a turnover of six hours or less are ideal for UV. Turnover rates above six hours will see less impressive results with UV.

Another factor that should be considered when sizing a system is bather load. A lap pool will produce less chloramines relative to a zero-entry, activity pool, one with spray features or a high bather load. UV provides the most dramatic benefit where the formation of chloramines is readably apparent. Additionally, pools with a high number of infants, elderly and immune compromised will receive a higher level of assurance due to the disinfection properties of UV.

Industry Direction

Many states require NSF Standard 50 for equipment installed on public pool filtration systems. While amalgam UV is more popular for most industrial applications, due to its efficient and low-cost nature, only medium pressure UV systems are currently available with a NSF 50 certification. Many aquatic architects even require NSF 50 when designing pools in states which do not require this standard.

The industry has repeatedly been presented with technologies which proved to be less than effective and the litigious nature of our society, and more specifically the aquatics market, has forced designers to proceed cautiously. It is expected that multiple manufacturers will obtain NSF Standard 50 for amalgam UV systems in this year and beyond.

The aquatics industry stands to lose or save a tremendous amount of money based upon which UV technology is selected. If energy prices increase as expected, these savings will become even more apparent.

Amalgam vs. Medium Pressure

                Amalgam                      Medium Pressure

Lifespan        Lamps last 9,000-12,000      Lamps last about 4,000
                hours                        hours

Temperature     Lamps operate at 150-250     Lamps operate at 1,500
                degrees                      degrees

Wattage         150-200 watts                2,000-5,000 watts

Effectiveness   More effective at reducing   More effective at
                monochloramines              reducing free chlorine

Rating          NEMA 4X rating               NEMA 12