By Jeff Boynton
Various halogens and sanitizers are used to treat waterborne pathogens in pool and hot tub water; however, as frequent reports on recreational water illnesses (RWIs) (i.e. Cryptosporidium [Crypto] and Giardia) and bacteria outbreaks abound in the press, many commercial pool operators and some residential pool owners are now incorporating a supplemental disinfection system (SDS) to assist in water sanitation.
For this reason, ultraviolet (UV) water treatment technology is one SDS that has seen increased popularity of late thanks to its ease of use, reduced chemical consumption, health advantages and environmentally friendly benefits. This article will explain what UV light is, how it can improve water and air quality in aquatic facilities, and which products are appropriate for particular pool types and sizes.
What is UV?
UV light is electromagnetic radiation emitted by the sun. It is an invisible light with a wavelength shorter than that of visible light but longer than X-rays. Its connection to water sanitation was discovered more than 100 years ago when European scientists learned the top surface of lake water was sterile when exposed to sunlight. This eventually led to the invention of UV bulbs.
The spectrum of UV light can be subdivided into four main categories, UV-A, UV-B, UV-C and Vacuum UV. The area between 280 and 100 nanometers (nm) is UV-C, which is also known as germicidal light.
How does it work?
UV sanitation systems have gained traction in the industry because of their ability to eliminate chlorine-resistant micro-organisms, which are common causes of pool closures worldwide. These systems reproduce UV radiation inside reactors via powerful lamps, which emit germicidal UV-C light that is used to disinfect pool and hot tub water. Facilities equipped with these sanitation systems consume fewer chemicals and allow sanitizers to be more effective.
UV-C light has the ability to cause permanent damage to a number of micro-organisms almost instantly as the water circulates and is exposed directly beneath the lamp. By disrupting the micro-organism’s DNA, protozoans, viruses and bacteria are unable to replicate and remain inert. This light, however, does not act as a residual and it does not work on dead zones in the pool or hot tub. It only sanitizes water flowing through the chamber.