How Does a UV Disinfection System Work?

Everyone deserves to have clean drinking water. In the past, though, that was not always possible. Most people were at the mercy of public water systems, and those systems sometimes delivered substandard water containing bacteria, chemicals, and organic material. Fortunately, technology has advanced to the point that whole-house water purification systems can deliver pure water that has a pleasant taste and is both odorless and contaminant free. Evo Water Systems even offers an additional level of protection that adds UV disinfection to their line of whole-house water filters and salt-free softeners.

What Does a UV Disinfection System Do?

UV disinfection systems are designed to destroy contaminants at the microbial level without the use of harmful or toxic chemicals. They provide an additional level of protection and security by eliminating microorganisms that are able to survive chlorine treatments, such as cryptosporidium and giardia. UV disinfection systems are able to destroy as much as 99.9 percent of bacteria and other microorganisms. Such systems are economical and provide protection on a 24/7/365 basis with very little maintenance. Because UV disinfection systems only target contaminants, they do not alter the water’s taste or otherwise degrade its quality. UV disinfection systems are extremely effective at producing bacteria-free water and leave no byproducts behind.

How Does a UV Disinfection System Work?

UV disinfection systems differ from other water purification systems because their sole source of water treatment is ultraviolet light. While a UV source may be added to a treatment system containing carbon filters, UV systems have no filters of their own and use no chemicals. Instead, they use a low-pressure monochromatic lamp to produce ultraviolet light that treats the water as it passes through the system. The treatment process is physical instead of chemical and provides instantaneous disinfection. The only maintenance required is that the UV lamp may need to be replaced about once per year.

Ultraviolet Light

The spectrum of light visible to the human eye includes wavelengths that range from 700 to 400 nanometers (nm). At the top of that range where the wavelengths are the shortest, light takes on a violet color. Ultraviolet light derives its name from the fact that its wavelength is even shorter than violet light and is therefore invisible to the human eye. It also has more energy than visible light. The sun is the primary source of natural ultraviolet light. Artificial sources include mercury vapor lights, halogen lights, certain types of fluorescent lights, arc welders, tanning beds, black lights, and some types of lasers.

UV Wavelength Designations

Ultraviolet light is broken down into different wavelengths designated as UVA, UVB, and UVC. UVA has the longest wavelengths that range from 400 to 315 nm. UVB wavelengths are in the middle at 315 to 280 nm, and UVC has the shortest wavelengths at 280 to 100 nm. Most of the ultraviolet light that reaches the earth from the sun is UVA. It is known to cause paint to fade and can pierce the skin, causing skin diseases including melanoma. Only a small portion of UVB reaches the earth from the sun. It can reach the outer layer of the skin and is known to cause the skin to tan and to suffer sunburn. No UVC reaches the earth’s surface from the sun because it is absorbed by the earth’s atmosphere.

The Effect of Ultraviolet Light on Bacteria

UVC has more energy than UVA and UVB and can be thought of as germicidal. When microorganisms are exposed to UVC, it penetrates their cell walls and destroys their DNA and RNA, effectively killing them. Because UVC does not reach the earth from the sun, bacteria have no previous exposure to UVC and therefore build up no immunity. With their DNA and RNA altered, bacteria are no longer able to replicate, which takes away their ability to cause human health issues.

History of UV Disinfection Systems

In addition to treating drinking water, ultraviolet light has been used for years in hospitals and certain industries to disinfect surfaces. The discovery that led to the use of ultraviolet light for germicidal purposes can be traced back to 1877 when Arthur Downes and Thomas P. Blunt published a paper claiming that sunlight suppressed the growth of bacteria. In the 1890s, Niels Ryberg Finsen developed an ultraviolet light source designed to treat tuberculosis of the skin, for which he was awarded a Nobel Prize. The device he invented was also used to treat other diseases, including lupus vulgaris. Later research shifted the emphasis to using ultraviolet light for preventing diseases rather than trying to cure them.

Why and When Do I Need a UV Disinfection System?

It has come to light in the past several years that much of the country’s aging infrastructure is deteriorating at the same time that demand is growing. Many public water systems have had pipes in the ground for more than a century. A substantial amount of that pipe is rusted and subject to breaks and leaks. Dig-ins, extreme droughts, and other environmental conditions can also lead to underground pipe failure. When that happens, bacteria can enter the water system and be delivered to your home or place of business, including those that cause E. coli and Salmonella. Water treatment plants may also be shut down because of equipment failure or deliberate sabotage.

Boil Water Notices

When a line break or other system failure raises doubt that the water in a public water system is free of disease-causing organisms, government standards require that a boil water notice (BWN) be issued. The boil water notice will state that your water is not safe to drink unless it has been boiled. The reason for boiling the water is that high temperatures will destroy any bacteria in the water. Boil water notices are typically issued for at least 24 hours and sometimes for several days at a time. Unfortunately, boil water notices are becoming more common because of the aging infrastructure problems and increased demand mentioned above.

Number of Boil Water Notices Issued

As an example of the increasing number of BWNs being issued, the Texas Water Resources Institute has stated that the number of BWNs issued in Texas increased more than 70 percent between 2011 and 2016. They go on to say that the largest number of BWNs ever issued in the United States occurred in Texas in 2021 when more than 2300 BWNs were issued which affected over 14 million people. Texas isn’t the only state issuing an increasing number of boil water notices, though. It is a trend that can be seen nationwide. To add to the problem, public water systems are sometimes slow about issuing BWNs, and some customers don’t find out about the problem until they hear about it in the latest news.