Electric Disinfection Technologies

In response to COVID-19, commercial customers are seeking methods to safely return occupants to their buildings. This lab study will provide efficacy of several in-room light-based disinfection techniques.

KEY RESEARCH QUESTION 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? RESEARCH OVERVIEW Pilot-scale testing of UV-C LED pilot units was conducted in collaboration with testing partners U.S. Environmental Protection Agency (EPA) and AquiSense Technologies at the EPA Test and Evaluation Facility in Cincinnati, Ohio. Pilot-scale testing included collimated beam testing as well as flow-through testing for both drinking water and municipal wastewater. Testing included a series of challenge test runs targeting total coliforms; heterotrophic plate count (HPC) and Bacillus globigii in drinking water; and E.coli, Enterococcus, total coliforms, HPC, and Bacillus globigii in municipal wastewater. Collimated beam testing on several Legionella subspecies was also performed. For each challenge test run, water samples were collected and analyzed in EPA’s microbiology lab and performance results (log removal) summarized in comprehensive tables and graphs. Based on the test results, scale-up requirements for larger capacity UV-C LED disinfection systems at drinking water plants and municipal wastewater treatment plants were determined. In addition, energy use requirements were projected for UV-C LED disinfection of drinking water and municipal wastewater. KEY FINDINGS UV-C LED technology performs like conventional UV mercury vapor lamp systems in water disinfection applications. 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 energy use projection for UV-C LED disinfection of drinking water is in the 65–250 kWh/MG range. The energy use projection for UV-C LED disinfection of municipal wastewater is in the 250–300 kWh/MG range. The electrification potential of UV-C LED disinfection technology is an estimated 2.4 to 3.7 TWh per year in the U.S. public water supply and municipal wastewater treatment industries.   WHY THIS MATTERS The research findings in this report demonstrate that UV-C LED technology is a viable option for water disinfection. UV-C LED water disinfection systems offer numerous benefits over chlorination and conventional UV mercury vapor lamp systems, including mercury- and chlorine-free operation, much smaller footprint, and tailored wavelength for optimal disinfection performance. Electrification is significant in applications where UV-C LED disinfection can replace chlorine. HOW TO APPLY RESULTS 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.