This article originally appeared in Water Quality Products March 2020 issue as "Dare to Disinfect"
A new type of water disinfection product is making waves in the water industry: ultraviolet (UV) water disinfection systems that utilize deep-UV light-emitting-diodes (LED). UVC-LED water disinfection systems are now available on the market and offer the combined benefits of two gold-standard technologies; UVC germicidal irradiation and LED lights. This article discusses the significance of UV-LED technology, its application in water treatment, the prospect for their social and environmental impact, their current and future applications and what to look for when considering a UV-LED water disinfection product.
UVC-LEDs, often referred to as the deep-UV-LEDs, or simply germicidal UV-LEDs, are LEDs like the LEDs that are replacing halogen and incandescent light bulbs in the lighting industry but that produce a short and intense wavelength of light in the 250 nm to 280 nm range. The UV-LED is a invention that has only in recent years become powerful enough to effectively disinfect flowing water. They can now be used to design affordable point-of-use (POU) water disinfection solutions. Much research and development has gone into the development of UV-LED water disinfection devices, and it has become apparent that even minute details in the design of these devices can be as important as the power from the UV-LED itself. A highly efficient and affordable UV-LED water disinfection device is currently the product of a select few companies, each applying their own concepts on how to best utilize UV-LEDs. Current UV-LED water disinfection devices are ideal for POU applications, which is great news for consumer markets around the globe and for the appliance manufacturing industry, that have lacked a convenient and eco-friendly solution to microbial pathogen contamination in drinking water.
Water Disinfection Technologies & the Ecological Impacts
Millions of POU water purification systems and billions of water bottles are sold every month. These products make compelling solutions due to their low-cost and convenience. Bottled water aside, POU water purification systems make an ideal solution to various water contaminants and can be relied upon to make safe drinking water in many cases. Physical and chemical contaminants like sediments, heavy metals and industrial byproducts can be removed from water through a variety of mechanical filtraters and ion exchange technologies, but microbiological contamination poses a particularly difficult challenge. Cost-effective mechanical filtration is not usually rated for bacterial and viral decontamination, thus chemicals; sub-micron membranes; and mercury-gas based UV lamps are commonly used for the treatment of waterborne pathogens. Each of these disinfection methods have their own drawbacks which are addressable by the UV-LED water disinfection device.
From the common water disinfection technologies, chemical water treatments are the most widely applied. When properly used, the benefits of chemical treatments are undeniable, but their drawbacks, like the potential for overdosing if not properly administered; variable consumer acceptance between geographies and markets; and the innate chemical resistance of certain waterborne pathogens such as Legionella, Cryptosporidium, Giardia, and Cyclospora, have further driven development of alternative water treatment methods. Specially designed sub-micron filters and reverse osmosis (RO) membranes offer a defense against a variety of microorganisms, sometimes even against viruses, but usually require frequent replacements and incur a high maintenance and consumables cost. The use of mercury-based UV-lamps is the fastest growing water disinfection technology due of its universal dose-dependant germicidal effect and widespread acceptance. UV-lamps may offer the best defense against pathogens in water, but they consume high amounts of electricity; usually require frequent cleaning and replacements; and are an alarming source of mercury contamination and pollution.
Where safe potable water or a convenient and affordable water purification solution is not available, bottled water is king. Much has been written about the impacts of single-use water bottles on our planet’s various ecosystems, and the water treatment industry has rallied against water bottles and their plastic waste. Inadvertently, the gold-standard in water disinfection has become the UV-lamp, which poses perhaps an equally alarming problem through the impact of their mercury pollution. Mercury contamination in our oceans and food chain is a major cause for concern and is the subject of the United Nations’ Minamata Convention Against Mercury. UV-LEDs offer a mercury-free alternative to UV-lamps and are a truly eco-friendly solution to drinking water safety; plastic waste; and mercury pollution.
Applications for UV-LED Water Disinfection Devices
UV-LED water disinfection devices not only have the potential to replace mercury-based UV-lamps in their current POU applications, they can be applied to cases where UV-lamps have been unsuitable, will soon be appropriate for point-of-entry (POE) water disinfection and will eventually be applicable to centralized industrial scale water treatment.
POU applications where UV disinfection is a benefit, but where the UV-lamp has been unsuitable, present opportunities for novel applications of UV-LED devices. UV-LED devices can be made much smaller than a UV-lamp and can fit into more compact appliances; they can be switched off when water is not flowing, thus generate a negligible amount of heat as compared to a UV-lamp and are ideal for the disinfection of chilled water; they can be cycled off/on infinitely and can emit a UV pulse that is useful for bio-fouling prevention in water containers; they power-on instantly with no warm-up period, thus conserve electricity when switched off; UV-LEDs are powered with a direct electrical current, making them ideally suited for off-grid situations where a solar-cell, battery or even a hand crank is used as the source of electricity. Many of the novel application for UV-LEDs offer solutions that are particularly useful in the developing world, where electrical infrastructures are absent/limited or where maintenance requirements of the UV-lamp are prohibitive. UV-LED devices offer opportunities for water appliance manufacturers, water system installers and distributors to differentiate their products with a hassle-free water disinfection feature that represents a valuable level of comfort and added safety to their customers.
POE UV-LED water disinfection devices are beginning to appear on the market. The rapid evolution of the UV-LED and the design capabilities of select few UV-LED water disinfection system manufacturers have made whole home UV-LED devices possible. Higher-flow UV-LED devices are sold for a moderate premium, but the operational cost saving of these devices represent a substantially lower cost of ownership. These highly anticipated devices represent a compelling solution for residential well-water disinfection and will have a dramatic impact on the fazing-out of mercury-based UV-lamps.
Industrial or commercial UV-LED water disinfection devices may take several years to materialize, but it certainly seems that the barriers to the commercialization of such devices will soften over time. Replacing the mercury-based UV-lamp with a better UV-based technology in their industrial applications will be a major achievement for the UV industry.
What to Look for in a UV-LED Water Disinfection Device
Not all UV-LED water disinfection devices are created equal. Differences in UV-LED devices concepts have advantages in varying applications, design optimization concepts vary between UV-LED device manufacturers and result in varying efficiency, durability, and overall disinfection, and differences in terms of UV-LED device certifications should be considered when selecting a UV-LED product. UV-LED water maintenance devices and flow-through UV-LED water disinfection devices have different applications, and differences between flow-through devices have an impact on their performance and reliability.
The concept of a UV-LED water maintenance device typically refers to a chandelier style device used to prevent bio-film formation within a water storage container. These devices offer a low level of water disinfection but are a cost-effective solution for surface disinfection. One cannot rely on a water maintenance device for making safe water from a microbiologically unsafe source, as a chandelier style UV-LED device requires a long enough exposure time to provide an adequate level of water disinfection.
The concept of a flow-though UV-LED device offers a much more controlled environment for consistent water disinfection. Since the fluid dynamics, the flow and mixing rate can be better controlled, pathogens disinfection is more accurately optimized. As mentioned, the design of a UV-LED water disinfection device may be as important as the power of the UV-LED itself. UV collimation is one of the most efficient ways to maximize the germicidal efficacy of the UV-LED device. Much like a laser-pointer, optical lenses are used to create a focussed beam of UV energy within the UV-LED disinfection device and offers accurate and reliable disinfection performance. UV collimation devices perform independently of the reactor’s material properties and offer a sustained performance over the entire life of the UV-LED.
In terms of certification for UV-LED water disinfection devices; material safety; structural integrity; and disinfection performance are the main factors to verify. The leading standards in North America for these factors are NSF Standard 55 for UV drinking water systems and NSF Standard 372 for lead-free water drinking water products. Compliance with these standards indicates that the UV-LED device will not introduce any harmful chemicals into the water, can handle more than 200 psi of water pressure and will disinfect a safe level of microorganisms. Certification bodies like IAPMO, CSA and WQA can certify the compliance to the NSF standards, and end users can look to the bodies’ markings to verify that the proper NSF standards are referenced.
How to Source a UV-LED Water Disinfection Device
A simple web-search will indicate which UV-LED water disinfection products can be sourced for home use or appliance integration, and the information in this article can be used to guide the selection of the ideal device according its use case. As UV-LED technology evolves, the future of UV-LED devices in the water treatment market will only become stronger and more compelling. The benefits of UV and LEDs are undeniable as these are truly gold standards technologies in their own rights, and their combination makes for one of history’s most beneficial technological advances. POU UV-LED water disinfection devices offer a flexible and cost-effective residential drinking water purification solution with the prospect of reducing environmental impacts of water purification, and eventual POE and industrial UV-LED devices will eliminate the need for mercury in water processing altogether. Stay tuned as the future of the UV-LED is bright.