Ultraviolet Sterilization

From a robot that zaps operating rooms to a wand designed by Boeing to disinfect airplane tray tables, UV light is becoming more and more popular. And for good reason: it’s effective at killing many different types of bacteria, viruses and other harmful pathogens.


As with chemical or physical disinfectants, the effectiveness of UV treatment depends on the degree of inactivation achieved. This is governed by the amount of UV energy delivered (irradiance) and the length of exposure time.

Inactivation of Microorganisms

Under certain conditions, ultraviolet (UV) radiation is a very effective sterilant. Bacteria, yeasts, molds and viruses are readily inactivated, provided the cells are accessible to a sufficient UV dose. UV radiation damages the DNA of organisms by creating pyrimidine dimers that interrupt the replication cycle. Once the cell’s DNA is damaged, it can no longer reproduce and is unable to spread disease. Most bacteria are highly sensitive to UV light, although extremophiles such as the bacterium D. radiodurans are orders of magnitude more resistant to UV than most bacteria.

UV sterilization is often used to disinfect equipment such as safety goggles and instruments, and for sterilizing surfaces in biological safety cabinets (“hoods”) between uses. It can also be used for disinfecting water. However, the effectiveness of UVGI can be diminished by natural organic matter and certain inorganic contaminants such as iron, sulfites, nitrites, or suspended matter such as particulates or turbidity that can absorb or shield microorganisms from the damaging effects of UV radiation.

A Beer-Lambert law model was developed to describe the inactivation performance of three different UV sources toward aerosolized E. coli. The model was fitted to experimental data obtained from airborne E. coli inactivation tests under two UV average absorbed energy density conditions (15.2 and 36.1 W/m3). The resulting inactivation efficiency versus UV dose graph indicates that the model fits the experimental data well.

Sterilization of Surfaces

While chemical or physical disinfectants typically require a specific concentration, contact time and temperature to inactivate microorganisms, UV radiation is instantaneous. UV sterilization systems are used in a variety of environments to eliminate harmful chemicals and to prevent the spread of bacteria, viruses, and fungi.

Food service establishments use UV sterilization to keep kitchen equipment and surfaces clean and germ-free, including utensils, counters, and refrigerators. UV disinfection is also used in sewage and wastewater treatment plants to eliminate bacteria, viruses, and fungi, as well as to reduce VOCs and industrial exhausts containing solvents.

Additionally, UV water sterilization is widely utilized to eliminate harmful pathogens from drinking and bathing waters and for cleaning and sterilizing process piping and drain pans. Many hospitals and healthcare facilities utilize UV sterilization to sanitize commonly touched surfaces and circulating air.

UV sterilization is even being employed in home use to disinfect items like toys, pacifiers, and baby bottles (though it has not been proven to kill the COVID-19 virus). With a wide range of products available, from bots that sterilize countertops, to wands for wiping down sketchy hotel sheets, to gizmos that will zap your stinky shoes, it is important to follow manufacturers’ instructions on light-source distance, exposure time and safety precautions. The current COVID-19 pandemic underscores the need for effective, reliable and cost-effective UV disinfection solutions to minimize viral transmission. This paper presents a technical-rich critical review of scientific fundamentals of UV dose requirements for disinfection, protocols for performance validation and safety considerations for the application of UV to biocontaminated media.

Sterilization of Water

Ultraviolet sterilization can be used in many applications to disinfect water. It is effective for destroying bacteria, viruses, yeast and mold spores. It is also used in food production and processing to prevent contamination. It can be installed in factories to sterilize drinking and process water.

UV light is germicidal, or disease-inhibiting, at wavelengths ranging from 100 to 280 nm (ultraviolet A, ultraviolet B and ultraviolet C). The sensitivity of microorganisms to UV radiation has a peak around 265 nm. This wavelength is considered to be the optimal range for UV sterilization of water, because of its high germicidal effectiveness and its relative safety.

It has been shown that UV can sterilize water, but the degree of sterilization depends on a number of factors, including UV intensity and exposure time. Additionally, a system’s ability to deliver an adequate UV dose varies, due to differences in the distribution of UV irradiance throughout its treatment volume, and differences in the pathways through which water flows.

Most importantly, it is essential that a UV treatment system be properly designed and maintained to ensure the highest level of disinfection. To achieve this, pre-filtration is typically required to remove particulate matter and color, as well as to reduce the turbidity of the water. This will allow for an even distribution of UV light over the entire treatment volume, and enable maximum efficiency.

Sterilization of Air

The sterilization of air is a common use for UV light, and it has been proven effective against a variety of harmful pathogens, including tuberculosis (TB), according to a Rensselaer Polytechnic Institute Lighting Research Center public health report. Many commercial and residential UV disinfection systems rely on UV germicidal irradiation to control bacterial growth and prevent the spread of disease.

Germicidal lamps emit short wavelengths of UV radiation that are effective against germs on surfaces and in water. They destroy the nucleic acid of the microorganism, preventing it from reproducing or infecting other organisms. The light is also non-toxic and produces no byproducts. This is why it is the preferred method for disinfection of water, air and many other substances in industrial, commercial and residential settings.

In fact, a number of devices ranging from a robot that zaps operating rooms to a wand that disinfects sketchy hotel sheets and a gizmo designed by Boeing to sanitize stinky shoes are now available that use UV to kill a wide range of dangerous bacteria and viruses. It’s important to note the distinction between sterilization, disinfection and decontamination: Per the CDC, sterilization is a process that kills all forms of microbial life. Disinfection, on the other hand, can be accomplished through physical or chemical means. Decontamination is a step that removes most, but not all, microbial material from inanimate objects.