Water Conditioning & Purification Magazine

The Light Side Versus the Dark Side of UV-C LEDs: Validation, Claims and Current Applications

By Oliver Lawal and Mitchel Hansen

Ultraviolet light-emitting diodes (UV-C LEDs) provide new opportunities for water treatment. Over the past decade, they have increased in power and reduced in cost, providing UV equipment design engineers something over which to obsess. The expansiveness of this technology provides the possibility for whole new applications to be explored.

Does this new technology offer a bright new future of opportunities and science-based solutions or a dark side filled with little regulation and understanding of the limitations? This question looks at emerging UV-C LED technology through two distinct lenses. One, which is optimistic, perceives small UV LED disinfection systems as easily integrated and able to tackle problems never before possible with conventional UV lamps. The other, more dangerous view, perceives a lack of design rigor and validation, coupled with over-reaching marketing claims.

Why is this even a question? What is wrong with applying existing UV technology regulations to UV-C LED technology? This is not a unique case. As a rule, applying existing regulations to new technologies restricts the innovative nature of the new technology, preventing it from fulfilling its potential. Consider the requirement for an exhaust pipe to exit the rear of an electric-powered car. The opposite case also applies where there is potential for exploitative approaches to be taken. Consider an electric car claiming to be emission-free, while ignoring the electric power generation needs for recharging.

Consider the system
UV-C LEDs themselves get a lot of attention for their specific characteristics:

  • Compact footprint
  • Selectable wavelength
  • Instant on/off
  • Mercury-free

They are, however, merely one component in a complete UV water disinfection product—batteries in an electric car, for example. The complete UV system must be considered. Ultimately it is the UV system that must deliver the required disinfection and, while wavelength and power are important, so too are fluid dynamics and intensity distribution. The number and variety of water disinfection applications for UV-C LEDs are large but can be simplified into four categories (see Figure 1).

Each of these categories offers different solutions for different customer needs. Static disinfection is viable if the water remains in an appropriately sized tank for a designated time period, with a correctly sized UV lamp placed in the correct location, in addition to other design characteristics. Active flow processes require advanced system engineering, as UV intensity and residence time in the reactor are key to applying the appropriate UV dose in a single pass. Intelligent design is required to provide reliable and consistent disinfection results and the necessary control interfaces: on/off switching, alarm reporting, etc.

Some mercury lamp-based UV systems now available are marketed based on microbiologically verified testing and computational modeling verification. For the new generation of UV-C LED low-flow systems, the trend seems to be heavily weighted toward microbiologically verified sizing. It is not uncommon, however, to see products challenged using E. coli and the performance reported as a percentage inactivation.

The use of E. coli is particularly troubling for UV systems (due to its relative ease of inactivation, giving poor transferability to other, more resistant, microbial species) and the high degree of variability between various E. coli strains. Using a dedicated test organism, such as MS2 phage (see Figure 2), is both more predictable and provides verification with a high level of safety margin. For example, a UV dose of 30 mJ/cm2 will achieve ~1.5-log reduction of MS2, but a 3-log reduction of E. coli. A UV dose of 10 mJ/cm2, however, shows widely different results between these two pathogens with 0.5-log reduction in MS2 and 2.5 from E. coli. The non-linearity and relatively low UV inactivation level of E. coli makes it a poor test marker. Sizing UV product performance to one of the easiest pathogens to inactivate is akin to testing an electric car’s miles per charge while driving down a hill with the wind behind you. This type of microbiological validation causes the end user to question the validity of the technology, forcing them to run tests of their own to either verify the performance for their needs or to simply pass on this technology for a later date when regulations are in place. Luckily there are manufacturers that have provided credible third-party validated performance and their products have begun to be implemented into real-world applications (see Figure 3).

UV-C LEDs already integrated
Steam ovens. Professional steam ovens combine dry heat and steam to offer advanced cooking options to professional chefs. Steam ovens with UV-C LED disinfection offer low-temperature steam ovens require an easy-to-implement, compact and reliable UV system to be integrated into their ovens as the temperature is not high enough to disinfect on its own. (A UV-C LED solution was chosen due to its compact size, low power consumption and proven efficacy in eliminating food-borne pathogens during the testing stages.) The use of the UV LED system provides enhanced food safety and quality without adding hazardous materials to the process. The single LED device UV system in this example provides a UV Dose of over 20 mJ/cm2 at 1.2 Lpm, offering over 3-log reduction of multiple target pathogens, such as Listeria, Salmonella, and E. coli.

UV-C LED disinfection for bottle fillers
The key goal of drinking-water system manufacturers (bottle fillers, water coolers, bottleless coolers, etc.) is to provide clean drinking water with low environmental cost. A new endeavor in a bottle-filler product line provides POU disinfection through a UV-C LED system. Preventing in-line bacteria growth is a growing concern for water-cooler companies and working with leading UV-C LED-system manufacturers enables UV technology for their product lines. The UV-C LED system provides 2.5 Lpm at 40 mJ/cm2 offering point-of-consumption protection from waterborne pathogens and biofilm growth in the bottle filler. This technology provides both clean water without the use of chemicals and offers low power consumption and less frequent replacement intervals, reducing the environmental footprint of the system as a whole.

Conclusion
It is an exciting time to see the development and new application of LED technology in water treatment processes. Tens of thousands of UV-C LED-based products have been produced over the past year, and volumes are increasing exponentially. As the list of these products grows, however, the question of safe implementation needs to be addressed. The responsibility for design, production and operational quality largely sits with the manufacturer. At present, manufacturers are taken at their word that their products meet their marketing claims. System integrators (OEMs) should (and in most cases do) require manufacturers to verify their claims in scalable production.

Spurious product claims risk the health of unassuming end users across the world, with the potential to degrade trust in UV systems and set an unnecessary barrier to the widespread implementation of a technology with so much promise. While some marketing claims for these products can distort the true ability of their products, other companies hold themselves to high standards. Manufacturers who can show third-party validation of their products are set to succeed until regulations become standardized for this new technology. As time passes, it will be apparent which UV LED system manufacturers are following this rule based on the OEM suppliers that chose to partner with them.

About the authors
Oliver Lawal, Founder and CEO of AquiSense Technologies, has been involved in the development of UV LED disinfection systems for more than a decade and has been involved in the UV industry for 20 years. He is also the President of the International Ultraviolet Association.
Mitch Hansen is the Marketing Specialist with AquiSense Technologies and has been an advocate for UV LED technology for several years, promoting their benefits over conventional applications.

About the company
AquiSense Technologies is the global leader in UV-C LED systems design and manufacture. The company works with leading LED manufacturers to evaluate their devices and then design efficient disinfection products. Using a combination of patented technology and in-depth know-how, the company integrates LED devices into products that solve real-world problems in water, air and surface applications. Contact: info@aquisense.com

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