Ultraviolet (UV) light treatment is a widely recognized and proven method of disinfection of water. Its s a physical treatment, not chemical, so it doesn’t alter the water chemistry.
The main advantage of this treatment is that it doesn’t alter the water chemistry, because the treatment is physical, not chemical. As a result, it doesn’t add color, odor, taste or flavor to the water, and doesn’t generate harmful by-products.
In recent decades, ultraviolet (UV) disinfection has become an appealing technology in the global water treatment industry due to declines in UV equipment costs and increased concerns about chemical disinfection.? Although UV disinfection typically employs a conventional mercury vapor lamp, a relatively new technology is poised to make that lamp a thing of the past.
NSF International, the body accredited by the American National Standards Institute (ANSI), has established new criteria for the use of UV-LED technology for microbial reduction.
Initially developed in 1991, NSF/ANSI 55’s scope was limited to low-pressure ultraviolet (UV) radiation systems using low-pressure mercury bulbs, which was the only technology available in the marketplace at the time.
In 2014, the Drinking Water Treatment Units Joint Committee responsible for the NSF/ANSI standard began developing a protocol to address newer alternate UV technologies. Lab testing showed that ultraviolet LED technology is effective at reducing bacteria and other types of microorganisms in drinking water. The task group ran a direct log-reduction test with an organism that would represent an entire class of organisms. They concluded that the virus Q-beta is an acceptable surrogate to?Rotavirus?and the test method performs appropriately. This holds true at both ends of the UV wavelength range examined (254 nm to 285 nm).
The existing protocol for current systems that uses pressure mercury bulbs will remain in NSF/ANSI 55 for at least five years. Manufacturers will have the option to evaluate their product to the new test method or the older test method defined within the standard. For devices with wavelengths other than 254 nm, the new method using Q-beta would be required and would have the following criteria:
- 4-log reduction of Q-beta at the alarm set point for Class A devices
- 1.5-log reduction of Q-beta for Class B with UV source irradiance at 70% normal output or 2.14-log reduction with UV source irradiance at 100% normal output
The use of UV-LED technology to treat microorganisms proves to be much safer for the environment. However, chemicals, such as chlorine, in many cases remain the primary means of purification. Chemicals can be toxic to aquatic life, create harmful byproducts, and are not effective against all pathogens (such as Cryptosporidium). The chemicals used for disinfection are also highly corrosive and can cause safety and environmental risks during transportation and storage. (NSFC, National Small Flows Clearinghouse). On the other hand, although UV disinfection is considered safer than chemical use, all conventional UV lamps typically contain 20-200 milligrams of mercury and are susceptible to breakage during transportation, handling, and operation. Conventional UV lamps hold their mercury either in a liquid form (more common in medium pressure lamps) or in an amalgam (more common in low pressure, high output lamps). Accidents and improper procedures increase the risk of exposure. The new criteria for the use of UV-LED technology for microbial reduction offers an alternative to potentially harmful mercury bulbs and it’s a giant step for environmental technologies.