Applications of UV-C LEDs

There are many applications where UV-C LEDs are being tested to see if they can become a solution to not just current disinfection challenges but our future ones too.

Drinking water disinfection, water purification, and treatment are where the technology is gaining traction as the solution is chemical-free, has no risk of creating harmful by-products, is an effective pathogen inactivation, and is very low maintenance.

As well as water, UV-C LEDs are offering disinfection for both air and surfaces. UV-C LED air purifiers for HAVC (heating, ventilation, and air conditioning) are being used increasingly in the commercial landscape.

There are numerous applications, from residential to commercial, healthcare, transport, life sciences, defence, and emergency response where UV-C LEDs are finding new uses:

UV LED Benefits 

UV-C LED Technology – The Next Revolution

In much the same way that LEDs have revolutionized the display and lighting industries, UV-C LED technology is set to provide new, improved, and expanded solutions in both air and water treatment. Dual barrier, post-filtration protection is now available where mercury-based systems could not previously have been conceivably used.

LEDs produce a selected wavelength from a small amount electricity. Depending on the composition of the LED it can produce anywhere from infrared, visible, and now UV-C wavelengths. 
The side view of the LED shows that as power passes through the LED layers, it activates the desired wavelength. 
The LED is then packaged to allow for electrical connection, thermal management, and physical protection. This helps maintain efficiency for the LED output and lamp life.
These LEDs can then be integrated into various systems to treat water, air, and surfaces. These systems also work with the LED packaging to disperse heat and improve efficiency of the disinfection process.

Back of lamp module with LEDs integrated

Front of replaceable module with thermal management options

Types of UV-C LED Disinfection Systems

UV-C LED technology is now being used for water dispensing and water-cooling applications and requires expertise, experience, and significant engineering knowledge to integrate this technology. 

To date, there have been three types of disinfection system concepts for integrating UV-C LED systems.

Inlet Disinfection System 

For pre-existing water systems, the disinfection process is often left outside of the device, which can leave an opening for bacteria to grow at any point in the system. In the inlet model, the UV-C LED is easy to replace and will last considerably longer than its mercury-vapor counterpart. 

While there is no need to redesign existing systems, the trade-off of having an inlet system is that the components are visible and are therefore more susceptible to damage.

In Process Disinfection

In this configuration, UV-C LEDs are integrated into the current system. This set up has several benefits: the UV-C LED component is protected, the amount of contamination between unit and dispenser is significantly reduced, and this model makes use of the compact nature of the LEDs.

The one major drawback to the in-process disinfection model is that it is susceptible to retrograde contamination and bacteria growth up the pipeline. 

Point of Consumption Disinfection

This system offers the greatest amount of protection by taking advantage of the full attributes of UV-C LED technology. Installed at the point of consumption, the system features an instant on/off switch.

​Point of Consumption disinfectant systems have the most benefits, but due to the complexity and expense of the new system, they are the most complicated to install and design.

They can become contaminated by an external source, in which the bacteria can grow through the pipe into the system. This can be prevented by the regular cycling of the system. 

Disinfection of Drinking Water

One area where UV-C LEDs are proving to be successful is in the disinfection of drinking water.

UV-C LEDs are being to disinfect drinking water at various points in the treatment cycle, from source to consumption. It can take a few seconds for the water to become clean in a UV-C model, and the new technology allows for LEDs to be placed at a different point to ensure decontamination.

It works initially when a water reservoir is exposed to a number of high-powered LEDs that disinfect the water. They emit powerful UV-C photons in the range of 200 – 280nm that pass through the water, stopping the bacteria in the water from being able to reproduce.
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Many newer systems have taken advantage of the compact size of the LEDs and can disinfect at the end stage of the drinking water journey – ensuring complete disinfection.

What is LOG reduction?

LOG reduction is used to measure how thoroughly a decontamination process reduces the amount of contamination. 
 
For example, 1-log reduction means the number of bacteria is 10 times smaller, 2-log equals 100 times smaller, 3-log equals 1,000, and so on.
 
To put this into perspective, if a surface had 100,000 microbes present, it would take 5-log reduction to bring the number of microorganisms down to just one. 

Water Treatment and Pathogen Control 

A recent paper released in Science of the Total Environment journal looked at various microbial disinfection methods for UV-LED water treatment systems. It found that UV-C LEDs were effective in the inactivation efficiency and energy consumption of UV-LEDs for pathogens at various wavelengths.

As UV-C LEDs can select various wavelengths to target specific microorganism present in infected water and deactivate them, different pathogens and bacteria stop replicating when they have been exposed to different wavelengths.

UV LED Benefits: Mercury-free

Although UV disinfection is generally considered safer than chemical disinfection, all conventional UV lamps typically use between 5-200 mg of mercury per lamp. 

These UV lamps require routine replacement and are susceptible to breakage during transportation, handling, and operation. UV LEDs are mercury-free and provide a safer alternative. This has created new markets for UV disinfection where traditional UV lamps containing mercury were banned for safety reasons (e.g., medical devices, space).

Conventional UV lamps hold their mercury either in a liquid form (more common in medium pressure lamps) or an amalgam (more common in low pressure, high output lamps). Amalgam UV lamps contain solid “spots” which consist of an alloy of mercury and another element, such as indium or gallium. Liquid mercury lamps have the potential to be hazardous both during operation and when the lamp is off. While the lamp is operating the mercury vaporizes; if the lamp is broken, mercury vapor is easily dissolved into the treated product. Accidents and improper procedures increase the risk of exposure to people and the local environment.

UV-C LEDs do contain small amounts of elements such as the metals gallium and magnesium and the metalloids silicon and boron (although boron is not predominantly used). These metals and or metalloids are bound within a stable crystal structure and cannot leach into the environment.

The inherent stable crystal structure of an LED ensures that UV-C LEDs are very robust to mechanical or environmental shock.

UNEP Minamata Convention

The Minamata Convention on Mercury was initiated by the United Nations Environmental Programme (UNEP) to protect human health and the environment from anthropogenic emissions and releases of mercury. The UNEP has set the goal for mercury to be phased out of production by the year 2020.

Although the Minamata Convention does not specifically prohibit the manufacture and sale of UV mercury-vapor lamps, it will provide a generally positive influence for the more widespread adoption of alternative technologies. Potential responses may include the following actions:

• Corporations that use UV systems in products or manufacturing processes (e.g., white goods, beverage, microelectronics, life sciences) may implement best practices by selecting an LED option by the influence of the Minamata Convention, not by enforcement.
• Original Equipment Manufacturers that currently employ conventional mercury lamps may see a conflict with the use of mercury-based products to their own environmental policies and, based on Minamata regulations, might start a transition to develop new products using mercury-free light sources.
• Municipalities may also follow suit in adopting UV-C LEDs, although it is more likely that they will require more time to adopt the new technology.
• There will always be a percentage of people that will look for “eco-friendly” product options. As the Minamata Convention raises awareness of the effects of mercury, it inherently affects the use of mercury-based lamps without banning the sale or manufacturing of these lamps.
• Regulators will likely have a slow transition from mercury to UV-C LED lamps. Regulators will always look for viable alternatives to mercury, as it is their mandate to steer technology to the most holistically sound solution.