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Q&A: Talking With Jacobs Water-Market Ultraviolet Disinfection Leads, Todd Elliott and Paul Swaim

Todd and Paul answer our questions about COVID-19 and Ultraviolet Disinfection

We connected with Todd Elliott and Paul Swaim, Jacobs’ ultraviolet (UV) disinfection technologists to talk COVID-19 and UV disinfection advancements. Read more in this interview.

Todd, Jacobs’ U.S. North Regional Solutions Lead, is currently a member of the Board of Directors of the International Ultraviolet Association (IUVA). Paul, Jacobs’ U.S. West Solutions & Technology Director, is a former President and former member of the Board of Directors of the IUVA. The IUVA (  has nearly 600 members across six continents. It is a not-for-profit educational association and the preeminent source of information on ultraviolet (UV)  technology as applied to water, wastewater, reuse and air treatment.

The IUVA has developed a fact sheet (, advice statements, white papers, and other key messages related to the use of UV technology for disinfection applications related to the virus (SARS-CoV-2) causing COVID-19.

We connected, virtually, with Todd and Paul to talk COVID-19 and UV disinfection advancements.

How did you each start working in the field of UV technology application?

Paul: Early in my career (way back in the early 1990s), I worked on pilot testing and design of UV disinfection systems for wastewater treatment plants, as well as a number of drinking water treatment projects. Then, when UV disinfection was shown to inactivate Cryptosporidium and Giardia in drinking water treatment in the late 1990s, I got involved in several of the first projects implementing UV disinfection at water treatment plants to improve public health protection.

Todd: I was first introduced to UV disinfection during my engineering coursework at University of Wisconsin Madison as part of my senior design project and later at the Nine Springs wastewater treatment plant as part of my masters research project. When I started my engineering career in Denver, Colorado, I worked on several wastewater UV disinfection designs with Paul Swaim and later we worked together on what were, at the time, some of the first UV installations across North America at drinking water treatment facilities. I was always interested in UV disinfection, so it was a fun and exciting time to enter the industry.

What excites you about your UV disinfection projects?

Paul: Like so many of my colleagues, I chose this career to make a positive difference in our communities. My first UV disinfection project was to study and then design a large UV disinfection system to replace a gaseous chlorine system. It was rewarding to improve safety for the surrounding area by eliminating the need to transport gaseous chlorine to the site and to improve safety for the plant operators at the facility too.

For drinking water, UV disinfection is a key tool in our toolbox to deploy as part of a multiple barrier disinfection strategy. On the more than 50 UV disinfection projects Jacobs has completed for water treatment plants, UV disinfection serves as an effective disinfection barrier for the pathogens that the U.S. Environmental Protection Agency (and other international regulatory agencies) regulates including Giardia and Cryptosporidium. Todd’s project in Cedar Rapids uses UV disinfection as an accredited barrier for virus inactivation.

Todd: Watching an engineering project evolve from concept to reality is one of my favorite things about what I do. I’ve had the pleasure of helping dozens of utilities select the best UV application for their system and assist with design, installation, and commissioning of the selected system, including the mega UV disinfection system supplying New York City. UV disinfection systems are unique in that they involve sophisticated design and modeling to develop, but once in operation they are very simple and practical to operate and take up a fraction of the footprint when compared to other technologies. It’s also exciting to see UV disinfection being applied to the growing water reuse market in California and elsewhere, where the additional pathogen barrier it provides is so critical.

Paul: The application of UV disinfection in the water market has been one of our most important breakthroughs of the past few decades. At wastewater treatment plants, the use of UV disinfection makes for a safer work environment, reduces risk and improves water quality in the environment. At drinking water treatment plants, the use of UV disinfection improves public health protection through the multiple disinfection barrier approach. It’s been very rewarding to have had a hand in lots of projects with these great outcomes.

We know ultraviolet (UV) light as causing sun tans and sunburns in human skin. Most of us wear our sunscreen with UVA and UVB protection. Now we’re hearing about UV light being used as a disinfectant to kill viruses. Can you tell us what UV disinfection is and how it’s used?

Todd: Before getting into the specific details of UV disinfection and how it works, let’s do a quick high school physics refresher about the electromagnetic spectrum. The sun radiates a broad stream of electromagnetic energy to our planet, including visible light and UV light. The ultraviolet range is “light” that exists just beyond the visible light spectrum with wavelengths under 400 nm. UV light is divided into 3 main groups: UVA, UVB and UVC. All three groups of UV light can cause adverse health effects like burns and skin cancer, but only UVA and UVB rays make it to the earth’s surface. UVC rays are blocked by the earth’s ozone layer.

The UVC range is considered the “germicidal” range of UV light in the 200 to 280 nm range and is generated using mercury vapor lamps or LEDs and applied to air or water for disinfection. It is also used for surface curing or treatment in specialty industrial applications.

Where is it currently being used?

Paul: Scientists first discovered the germicidal benefits of UV light in the late 1800s, but it wasn’t until the last 50 years that UV disinfection really gained widespread use in the municipal water and wastewater market. Early adoption of UV disinfection focused on disinfecting wastewater treatment plant effluent in order to reduce levels of bacteria and other pathogens and as an alternative disinfectant to chlorine gas, as mentioned previously.

Todd: In the past few decades, UV disinfection has expanded into the potable water disinfection market for inactivation of pathogens like Cryptosporidium and Giardia. For example, the primary water supply to New York City, about two billion gallons per day to over eight million residents, is disinfected with a combination of UV disinfection and chlorine.

Paul: The Cedar Water Treatment Plant that we designed to serve Seattle, Washington, provides about 2/3 of the community’s water demand, and we’ve operated the water treatment plant with UV disinfection for well over a decade.

Todd: And many industries, hospitals and even private homeowners use UV disinfection to disinfect their water supplies and air ventilation systems.

How does it kill viruses?

Todd: Viruses are microscopic organisms, smaller than bacteria, and rely on a host cell to thrive and reproduce. They contain single stranded or double stranded RNA or DNA inside of an outer casing of proteins. UVC light inactivates (aka, “kills”) viruses by damaging the RNA of the virus, rendering it unable to reproduce and infect its host. This differs from chemical based disinfectants or simple soap and water that physically damage the outer protein layer, effectively “killing” the virus.

Can it kill SARS-CoV-2?

Paul: Many researchers in the public health arena are trying to answer this question right now. UVC light has been used extensively for nearly 50 years in disinfecting drinking water, wastewater, air, and surfaces against a wide range of human pathogens, bacteria, and viruses. Some organisms are more susceptible to UVC disinfection than others. Organisms with double stranded RNA or DNA, like adenovirus, are typically more difficult to inactivate with UV disinfection. Adenovirus is the basis for virus inactivation requirements in water treatment, so it provides for a conservative approach.

Todd: We know that UV disinfection at 254 nm is quite effective at inactivating similar coronaviruses like SARS-CoV and MERS-CoV, which have a similar structure to SARS-CoV-2 and consist of single stranded RNA. An important caveat is that most of the research has been done in controlled, laboratory settings. In practice, applying UV disinfection may be more challenging. Nonetheless, from the IUVA fact sheet, the organization believes further testing will demonstrate that properly-applied UV disinfection can be used to effectively inactivate SARS-CoV-2 in water, on surfaces and in the air.

Paul: Recently, the IUVA published additional guidance that is worth sharing here. The IUVA stated: Because the COVID-19 virus (SARS-CoV-2) is so new, the scientific community doesn’t yet have a specific deactivation dosage. However, we know the dosage values for comparable viruses in the same SARS virus family are 10-20 mJ/cm2 using direct UVC light at a wavelength of 254nm; this dosage will achieve 99.9% disinfection (i.e., inactivation) under controlled lab conditions.”

Will it be used to kill SARS-CoV-2?

Todd: It is quite likely that UV disinfection will be used to kill or inactivate SARS-CoV-2 in healthcare settings. Robots with UV lamps attached have already been used to disinfect hospital rooms across the globe for general disinfection and will likely be applied to areas treating COVID-19 patients. The IUVA recently created a Healthcare Acquired Infection (HAI) task force with the goal of establishing UV disinfection standards for hospital settings. The ongoing COVID-19 crisis has pushed this initiative even further with a focus on disinfection of personal protective equipment (PPE) like N95 masks ( It may take a while for peer reviewed research to prove UV disinfection’s effectiveness with any certainty, but we’ll likely see its application for surface and air treatment in hospitals, long-term care centers, airports and even rental cars in the near future as the industry responds to immediate needs the COVID-19 pandemic demands.

Paul: I see several articles weekly on this topic, addressing using UV to disinfect everything from airplanes to subway cars to PPE. We can tell you to keep it outside your body though, and not to apply internally. More seriously, many of the fundamentals of effectively applying UV disinfection are the same as in water market applications. To disinfect effectively, UV light of sufficient intensity must reach the target pathogens for enough time.

What are the challenges with using UV as a disinfectant?

Todd: A big challenge in using UV disinfection is in applications where there are a lot of uneven surfaces. UV light will only disinfect surfaces it shines on, therefore, crevices and objects that create shadows can limit its effectiveness. Particles or organic materials in the air or water can also impede UV disinfection efficacy.

Another challenge is cost versus chemical based disinfectants, which are readily available and easy to apply. UV requires electricity, lamps, ballasts, control systems and safety features that increase the cost of ownership. In mature industries like drinking water and wastewater disinfection, UV disinfection is quite competitive in terms of costs. But in emerging markets like healthcare and LED based UV, it may be cost prohibitive.

Paul: In the drinking water, water reuse and wastewater industries, we have well-developed standards for applying UV disinfection effectively. For these emerging applications like Todd mentioned, the principles are the same: we need to get sufficient photons of UV light to the pathogens we are intending to disinfect. We look at a UV dose, based on the intensity of UVC light and time of exposure. In these emerging areas without clear standards for effectively using UV technology, not every device on the market is going to do exactly what it is advertised to do, so we would urge erring on the side of conservatism in applications – more exposure for longer time periods and making sure all surfaces are exposed.

Can it be used by individuals?

Todd: Yes, UV disinfection systems can be purchased for individual use, but Buyer Beware! The most typical application is point of use UV disinfection devices for water and they have been around for many years. They can be installed in a water bottle or on a faucet as a supplementary disinfection method.

Most recently, home UV disinfection systems for viral surface disinfection are now on the market.

Since it’s still an emerging application, there are very few accepted standards for equipment designed for UV disinfection of surfaces and few peer reviewed studies quantifying their effectiveness inactivating SARS-CoV-2.

In addition, UVC light is very dangerous if not handled properly. Any home UV disinfection unit should utilize NIOSH, UL or IEEE safety standards and be used in a safe location away from human exposure when operated.  A general rule of thumb for inactivating viruses like SARS-CoV-2 is to deliver a UV dose (intensity of UV light multiplied by time) of at least 40 mJ/cm2, which is equivalent to delivering 10 mW/cm2 of light energy for four seconds on a surface. A reputable supplier should have proper certifications, safety features, and evidence of effectiveness.

Paul: Recently, the IUVA released a document entitled, “Far UV-C in the 200 – 225 nm range, and its potential for disinfection applications” that cautions that “there is not yet sufficient evidence to support widespread application where direct human exposure is anticipated,” until sufficient evidence for safety is presented and suitable application protocols are established for this application of this type of UV light. Far UV-C uses lower wavelength UV light compared to water market applications of UV disinfection technology.

We’ve heard they’re looking at using UV to disinfect airplanes. How would that work?

Todd: There is currently high interest in alternative methods for surface disinfection, including airplanes. UV disinfection offers an alternative or supplement to chemical based disinfectants like chlorine or alcohol.

Airplanes have two potential modes of virus transfer: from air supply and from surface contact. The more routes an airplane takes in a day and the more passengers it carries, the higher the risk for transferring viruses between passengers and crewmembers.

Most airplanes utilize a large fraction of fresh outside air for its air supply and treat any air that is recycled using filters. UV disinfection could be applied to these air streams to inactivate viruses, but it is challenging due to the high volume of air to be treated. Surface disinfection of passenger seats, arm rests, folding trays is another application being investigated. It’s likely a combination of chemical based disinfection and UV disinfection, possibly using a hand wand UV light source or robot, will be used to disinfect airplanes between routes in the near future.

Are there other applications for UV disinfection that you’re seeing will result for the COVID-19 pandemic?

Todd: UV disinfection using LED technology is probably the most promising new development for the water industry. Currently, there is rapid development of LED based UV disinfection technologies for use in the healthcare industry due to its smaller footprint, lower energy use, and lack of mercury lamps. The COVID-19 pandemic has pushed the market immediately in this direction and has already been used in Wuhan, China, to disinfect air and surfaces for the highest risk areas with some success.  LEDs use semiconductor microchips to generate UV light, which means competing for suppliers for common electronic devices like laptops, cellphones, and HD TVs, which have a much greater market potential. The immediate interest for LED based UV disinfection in the healthcare industry will rapidly boost it into a mature market, increasing available products, improving system efficiency, and reducing LED costs. Eventually, these technologies will be applied to and benefit the water industry. This is very important for a water industry that lacks funding and research to drive markets in new directions.

Paul: We encourage people looking into UV disinfection for the first time to check out the IUVA web page for more information. Emerging UV technologies and applications have a lot of promise, but we need to have sound science behind these applications, particularly given the importance of disinfection. Our water and wastewater UV applications have a lot of science, regulations, and a long history of successful use behind them.

Never has disinfection been as important as right now. We hope all reading this are staying healthy and safe.


Todd Elliott has been serving as a drinking water quality subject matter expert for over 18 years. He has led the process design for dozens of water treatment applications throughout North America including numerous ultraviolet (UV) disinfection systems. Todd currently serves as Jacobs’ U.S. North Regional Solutions Leader for Drinking Water and Reuse and is a Board Member for the International Ultraviolet Association (IUVA).

Paul Swaim is a Senior Expert/Technology Fellow in Drinking Water and Reuse for Jacobs. He serves as the U.S. West region’s Director of Solutions & Technology. Paul has more than 30 years of experience leading drinking water, water reuse, and wastewater treatment projects from initial process selection through constructed facility startup and successful completion. Paul has been instrumental in delivering more than 50 disinfection projects across North America and internationally, totaling more than 2,300 million gallons per day of operating disinfection capacity.

At Jacobs, we’re always looking for dynamic and engaged people to join our team. Bring your passion, your ingenuity and your vision. Let’s see the impact we can create, together.

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