By now, many aquatics professionals have heard about the benefits of ultraviolet technology for reducing chloramines, especially on indoor pools. But many of these same professionals may not realize there are two distinct types of UV lamps — and that understanding the difference between the two can potentially save thousands.
Indeed, it seems aquatics professionals have so far ignored the most common, and inexpensive, type of industrial UV technology. That type of system is called amalgam, or low-pressure/high-output UV.
This system uses low-pressure UV lamps that are very similar to common fluorescent lamps. Both contain a small amount of mercury. The UV lamp tube is made of quartz, not glass. Quartz allows UV energy to pass through, while glass does not. These lamps emit UV energy at one specific wavelength, which is beneficial for chloramine control and disinfection. In the 1990s, low-pressure lamps were enhanced by altering the makeup within the lamp. The result was an amalgam lamp that could replace three common low-pressure lamps. Except for small applications, amalgam UV has become the most popular technology for the majority of industrial applications.
The other type of UV technology — medium pressure — is more expensive and more common in the aquatics industry. Medium-pressure lamps are designed to receive as much as 20 times the electrical power of a low-pressure lamp. The higher level of energy results in an output at every wavelength within the UV range.
Still, amalgam (low-pressure/high-output) technology seems to offer several advantages over medium pressure technology:
- Amalgam systems emit wavelengths of 254 nanometers, which is very close to the optimum wavelength needed for disinfection and chloramine control. In fact, a recent Duke University study concluded that amalgam systems are more effective at degrading monochloramines than medium pressure. The same study also showed that medium-pressure systems actually destroy more free chlorine than amalgam systems.
- Amalgam lamps are nearly three times more energy-efficient. That means amalgam UV offers significantly lower electrical costs.
- Amalgam lamps can last longer. Medium-pressure lamps are rated for up to 5,000 hours of life; amalgam lamps are rated for up to 12,000 hours.
- Amalgam systems have redundancy designed into the system. That means they typically contain three to six lamps, while medium pressure use only one. If an amalgam lamp is defective, the other lamps will continue to carry most of the load. There is, therefore, no loss of protection.
- Lamp temperatures do not require special controls for amalgam systems. Medium-pressure lamps operate at temperatures exceeding 1,500 degrees Fahrenheit. It is important to make sure the pumps are operational when the lamp is on. The surface temperature of amalgam lamps, on the other hand, is approximately 250 degrees Fahrenheit, and overheating is not a serious concern.
In almost every aquatic situation, it is less expensive to own and operate an amalgam UV system when compared with a medium-pressure system. The area where medium pressure may make more sense from a cost standpoint is when there are extremely high flow rates, such as a large outdoor waterpark. For chloramine control, a cost/ benefit analysis should be performed around 4,000 gpm.
Regardless of which system you choose, UV is a reliable, inexpensive and effective way to deal with chloramines.
Indoor aquatics facilities with UV systems will provide healthier environments for patrons and staffs. The question to be asked is not whether to use UV on an indoor pool; it should be which type is best.