Natural water supplies contain microorganisms that can make people sick. It’s important to professionally test and treat water before it is used for drinking, bathing or for filling swimming and paddling pools.
UV light sanitizers are available for home use. However, these devices may not be as effective as industrial UV sanitizers.
Inactivation of Microorganisms
UV sterilization (also called ultraviolet germicidal irradiation, or UVGI) alters the DNA of microorganisms by breaking certain chemical bonds and scrambling their structure. This renders them unable to reproduce and therefore, unable to spread infection. Unlike chemical or physical disinfectants, which require specific contact times and temperatures to work, UVGI systems simply expose the target organism to UV radiation. The type of UV wavelength and intensity affects the degree to which the organism is inactivated.
The most effective UV treatment involves the wavelengths 100-280 nm, or the ultraviolet C (UVC) spectrum. This is because only UVC possesses high enough energy to inactivate most waterborne microorganisms. This includes bacteria, the protozoan parasites Cryptosporidium parvum and Giardia lamblia, and viruses such as influenza.
When a microorganism absorbs UV, it causes pyrimidine dimers in its DNA. This disrupts the helix structure and prevents thymine or cytosine from bonding with each other as they normally would. This renders the organism unable to reproduce, and it becomes non-infectious.
While UVC sterilization isn’t a replacement for proven controls such as mask-wearing and social distancing, it can provide an extra layer of protection. Many UVC-equipped systems recirculate air or water to ensure all microorganisms are exposed to the UV light several times, and some will irradiate resistant organisms more than once. A recent study found that irradiating the SARS-CoV-2 virus with UVC reduced its transmission by 30%.
Inhibition of Biofilms
As a result of UV photolysis, certain chemical compounds in the cell are destroyed or degraded, thus making it impossible for microorganisms to reproduce. This is known as indirect disinfection. It is a slower process than direct damage caused by UV-B and UV-C wavelengths.
Biofilms are a major problem in the food industry. When pathogens in a biofilm come into contact with food, they can transfer to the surface and cause contamination. Using UV sterilization can help prevent this.
In addition to preventing pathogens from spreading, UV sterilization can also remove existing pathogens from food items. It is particularly useful in cases where food is exposed to pathogens for extended periods of time. This is because it can take days for a pathogen to be killed by conventional methods.
Research has shown that UV sterilization can destroy bacterial biofilms. In one study, it was found that a UVB radiation dose equivalent to 12 h of sunlight induced eradication of P. aeruginosa biofilms after 24 h of growth. This eradication level was comparable to that of antibiotic treatment with tobramycin at 100 times the MIC. The results suggest that combinatory treatments that combine light application and antibiotic administration may be able to overcome the resistance to treatment observed in chronic biofilm infections. This could lead to new strategies for the treatment of difficult-to-treat bacterial infections.
Inhibition of Bacterial Growth
Unlike chemical or physical disinfectants that require a certain concentration, contact time or temperature to inactivate a microorganism, UV-induced damage is instantaneous. When a microorganism is exposed to optimum UV wavelengths, its DNA (fundamental building block) is damaged and it cannot reproduce. If it can’t replicate, it can’t cause infection.
Ultraviolet radiation has also been shown to prevent the growth of biofilms. Depending on the size of the system and the amount of UV energy applied, the length of exposure and distance between the light source and the surface of the target biomolecules, the sterilization process may take as little as 1-2 minutes for a petri dish containing E. coli.
Similarly, UV disinfection is very effective against the most common waterborne bacteria. Many large wastewater treatment plants use UV to ensure the water they produce is free of harmful organisms. It is also used in aquaria and ponds to prevent unwanted pathogens from spreading.
Some research has indicated that UV can inactivate protozoan cysts such as Cryptosporium and Giardia lamblia, which can be difficult to eradicate with traditional disinfectants. The latest research, however, shows that a proper dose of 253.7nm spectral UV is extremely effective against these parasites. Our UV germicidal lamps are formulated to deliver the maximum, optimal wavelength for this purpose, and are incorporated into various air, surface and water sterilization systems around the world.
Inhibition of Virus Growth
Early studies showed that UV irradiation inhibited the growth of various microorganisms, but their susceptibility to this sterilizing effect varied greatly between species. In addition, the effects of UV irradiation are photochemical in the UVA and UVB ranges and progressively photothermal as wavelengths move beyond the violet-blue spectrum.
A number of research groups have also demonstrated the bactericidal effects of high-intensity UVC-LEDs (at four peak wavelengths from 266 to 279) against foodborne pathogens and spoilage microorganisms, with higher doses of irradiation producing greater reduction levels. They have shown that gram-positive and gram-negative bacteria and yeasts respond differently to UVC-LEDs, with gram-negative organisms showing the least resistance to irradiation.
Although it is not yet known whether the high-intensity UVC-LEDs used in this study can effectively inactivate SARS-CoV-2 or other coronaviruses, these results are encouraging. These newer disinfection methods could potentially be used alongside proven control measures such as mask-wearing and social distancing to help slow the spread of infection during the COVID-19 pandemic.
While UV sterilization is powerful and easy to use, it does have a limit. Because it only works in the area directly exposed to the light source, UV sterilization must be accompanied by other control measures to prevent contamination from other areas. This is why following the manufacturers’ instructions on distance from the light source, exposure time and safety precautions is so important.