Ultraviolet-C (UV-C) LED for Wastewater Germicidal Irradiation (UVGI)

Ultraviolet-C (UV-C) LED for Wastewater Germicidal Irradiation (UVGI) Much like light-emitting diodes (LEDs) have revolutionized the general (visible spectrum) lighting industry, UV-C LEDs are set to rapidly replace conventional UV mercury vapor lamps in water disinfection and water reuse applications. Although it is generally accepted that UV-C LED technology can be used for various water disinfection uses, steps need to be taken to verify performance and determine scale-up factors to support technology transfer to the high-throughput levels of municipal drinking water and wastewater systems. To this end, EPRI aims to evaluate the disinfection performance, reliability, and energy use requirements of small- scale, UV-C LED pilot units against contaminants commonly found in municipal drinking water and wastewater. Does UV-C LED technology perform like conventional UV mercury vapor lamp systems in water disinfection applications?

UV-C light has been used for several decades for water disinfection because it can render microorganisms inactive by altering their DNA and RNA to prevent microorganisms from replicating. Today, low-pressure high output, or medium-pressure mercury vapor lamps typically generate UV-C Light. However, and in much the same way that visible light-emitting diodes (LEDs) have revolutionized the general lighting industry, UV-C LEDs will rapidly replace conventional UV mercury vapor lamps in water disinfection applications. While UV-C LED systems for treating water at points-of-use applications are already commercially available and market competitive, larger-capacity UV-C LED systems for municipal application are still under development. In this project, EPRI challenged one vendor’s pilot-scale UV-C LED units with a range of water contaminants to evaluate its performance. EPRI conducted the pilot testing in collaboration with the US Environmental Protection Agency (EPA) and AquiSense Technologies (AquiSense) at the US EPA Test & Evaluation Facility in Cincinnati, Ohio. The pilot-scale testing included collimated beam testing and flow-through testing for both drinking water and municipal wastewater. The challenge test runs targeted total coliforms, heterotrophic plate count (HPC), Bacillus globigii, and Legionella in drinking water, and E.coli, Enterococci, total coliforms, HPC, and Bacillus globigii in municipal wastewater. The flow-through test results demonstrate: UV-C LED technology can provide a 2-to-3 log removal of the surrogate contaminate MS2 bacteriophage at a UV dose of 40-50 mJ/cm2 in drinking water. UV-C LED technology can provide a 4-log removal of E. coli at a UV dose of 25 mJ/cm2 in wastewater. The results show the UV-C LED technology is a viable option for water disinfection. UV-C LED systems offer numerous benefits over chlorination and conventional UV mercury vapor lamp systems, including mercury-free operation, chemical-free disinfection with no by-products, and tailored wavelength for optimal disinfection. The project team used the pilot test results to determine scale-up and energy use requirements for larger-capacity UV-C LED disinfection systems at drinking water plants and municipal wastewater treatment plants. We forecast the UV-C LED technology will require 65-230 kWh per million gallons to disinfect drinking and 250-300 kWh per million gallons to disinfect municipal wastewater. The electrification estimates for UV-C LED disinfection in the public water supply industry and the municipal wastewater industry are 0.2-0.3 TWh per year and 2.4-3.6 TWh per year, respectively. Keywords Water disinfection   UV disinfection  Ultraviolet light  Light emitting diode (LED)  UV-C LED Pilot-scale testing  Collimated beam testing  Flow-through testing   Project Results did transfer to a new measure. The results from this study show that it is technically feasible to use UV-C LED sources effectively for municipal water and wastewater disinfection. However, because the tests were carried out in a laboratory environment—that is, a controlled environment—additional tests conducted in a field setup in an actual water treatment facility would be necessary to demonstrate the scale and feasibility of this technology in a real-life, non-controlled environment. Lighting energy savings where not significant due to new LED UVC lighting system could required more fixtures compared to existing Mercury Vapor and at additional locations of the wastewater treatment process operations.