UV Rays: A shot in the arm for chemical water purification
Ultraviolet (UV) light has been naturally purifying water for centuries. With clear skies, the sun can destroy water-based pathogens in about six hours. Cloudy skies, pollution or unclear water causes imperfect conditions. These conditions allow for bacteria to grow and make natural water sources unsafe to use.
However, we have developed several types of water disinfection, ranging from chemicals to UV lamps. Although these are all beneficial to human health, some are more environmentally beneficial than others.
Advancements in chemistry and technology have resulted in multiple effective methods to purify water. Chemicals, such as chlorine, were the first widely used disinfection method and in many cases remain the primary means of purification. Chemical treatments dissolve pathogen cells entirely and, until ultraviolet (UV) treatment, were the best available option.
There are downsides to using chemicals in drinking water. They can be toxic to aquatic life, create harmful byproducts, and are not effective against all pathogens, such as Cryptosporidium. The chemicals used for disinfection are also highly corrosive and can cause safety and environmental risks during transportation and storage.
While it is unclear whether UV lamps for water disinfection will receive an exemption from various governmental regulations, it is clear that this alternative should be actively considered for the greater good.
All LEDs are known for their low energy consumption, and the same is true for UV-C LEDs when used in a quality disinfection system. Conventional mercury lamps require between 110 to 240 volts to operate, while LEDs require low voltage DC, meaning disinfection powered with a small solar panel or battery is feasible.
LED technology allows UV water treatment to be used in applications previously unavailable to conventional mercury lamps. Remote communities can easily purify water with solar power options, and mobile uses are now available due to the ruggedness and small size of the UV-C LED devices.
Applied at the point of use, additional safety can be provided to water in hospitals and research facilities without the need for storage tanks. UV-C LED technology is not just theoretical or in a concept stage. The Project is currently working on a device that will implement UV-C LEDs to disinfect water onboard the International Space Station. UV-C LED devices are currently available and ready to change the disinfection market.
The ideal wavelength to neutralise most bacterium is between 260–270 nm, however, it depends on the specific bacteria being targeted. Mercury lamps have two options: low pressure, which emit 254 nm; and medium pressure, which emit wavelengths between 200–300 nm.
LEDs have been a defining factor in many technological innovations, and water treatment is no exception. Although mercury lamp accidents are rare when lamps are installed correctly, the benefits of UV-C LEDs have begun to outweigh the need to stay with the status quo. Conventional ultraviolet treatment technology provided the world with an alternative to chemical water treatment. Now, with advancements in LEDs, we have come to the next stage of water purification.