Innovative UV-C LED Water Treatment Applications
Citation:
Goodrich, J., Helen Y. Buse, J. Hall, G. Hunter, R. Ehrhard, O. Lawal, AND C. Arzbaecher. Innovative UV-C LED Water Treatment Applications. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-23/128, 2023.
Impact/Purpose:
The U.S. Environmental Protection Agency’s (EPA) Homeland Security Research Program partnered with Washington University, St. Louis, and AquiSense Technologies to design, develop, fabricate, test, and deploy small-scale (< 10 gallons per minute (GPM)) ultraviolet light-emitting diode (UV-C LED) water treatment devices utilizing a Federal Technology Transfer Act (FTTA) Cooperative Research and Development Agreement (CRADA). The three parties initially signed the CRADA in March 2018, with a subsequent modification in June 2022. AquiSense Technologies develops integrated UV-C LED water, air, and surface disinfection systems. AquiSense Technologies supplied the project with two flow-through UV-C LED devices (a prototype and commercially available unit) and a collimated beam apparatus. The Electric Power Research Institute (EPRI), Black & Veatch, and Applied Energy Group provided project support. Most research occurred at the EPA Test & Evaluation (T&E) Facility in Cincinnati, OH, at the City of Cincinnati’s Metropolitan Sewer District’s Mill Creek Wastewater Treatment Plant. The goal of this CRADA was to investigate UV-C LED technology in various applications such as: 1. As a stand-alone modular water treatment unit process for multiple contaminants in various water streams 2. Integrated into a mobile emergency water treatment system in response to natural and intentional incidents where existing water The research study concludes that UV-C LED technology will become an effective alternative to conventional UV mercury vapor lamp systems for the disinfection of drinking water and municipal wastewater. Because of its smaller footprint and design flexibility, UV-C LED disinfection technology could expand into the industrial and niche water and wastewater markets as well as emergency community water treatment in response to natural and man-made incidents.
Description:
The project team evaluated the device at multiple wavelengths to assess optimal performance under specific conditions for select contaminants and a suite of contaminants. This collaboration focused on the following: - Reactor optimization and flow scale-up, - Modularity, - Packaging for rapid deployment, set-up, and take-down, - Easy integration with other water treatment unit processes, - Ability to uniquely design multiple wavelength reactors to target various water matrices, and - Dose vs. response of targeted contaminants. Ideally, the UV-C LED system will have low capital, operational, and maintenance costs; be easy to operate, and have a long working life. The development and evaluation of the device will include investigating multiple flow rates, integrated treatment and reactor design configurations, and variable background water quality characteristics. Many contaminants appear in drinking water and wastewater, and it is of interest to evaluate the efficacy and efficiency of the device on those: · - Biological warfare surrogates · - Chemical warfare surrogates · - Herbicides/pesticides · - Pharmaceuticals · - Flame retardants - Plasticizers There were different scales and scopes of research performed under this CRADA: - Low-flow disinfection with UV-C LED prototype device (0.5-1 GPM) · - Multiple wavelengths (255, 265, and 280 nm) · - Pilot-scale Legionella inactivation with a commercially available device (~ 2.5-3 GPM) · - Mobile emergency treatment of compromised community drinking water supplies (~10 GPM) First, pilot testing included collimated beam testing, as well as flow-through testing. The pilot testing encompassed a series of challenge test runs targeting total coliforms, heterotrophic plate count (HPC), Bacillus globigii (an Anthrax surrogate of Homeland Security interest) in drinking water, and E.coli, Enterococci, total coliforms, HPC, and Bacillus globigii in municipal wastewater. Next, EPA staff conducted collimated beam testing on several Legionella pneumophila serogroups. Water samples were collected and analyzed for each test run in one of EPA’s microbiology labs. Results showed the viability of the larger POE UV-C LED device incorporated into the Water-On-Wheels Mobile Emergency Water Treatment System (WOW Cart). Additional UV-C LED device integration into the WOW Cart occurred at the T&E Facility and Greater Cincinnati Water Works. The team conducted field deployment of the WOW Cart in response to tornados in Western Kentucky and floods in Eastern Kentucky. Pilot-scale test results indicate: · - UV-C LED technology can achieve similar log removals to conventional mercury vapor lamps for E. coli, Enterococci, HPC, and MS2 bacteriophage in both drinking water and wastewater. - UV-C LED technology can provide a 4-log removal of E. coli at a UV dose of 25 mJ/cm2 in wastewater. - UV-C LED technology can remove Bacillus globigii from contaminated drinking water and wastewater. Results show improved log removals over values reported in the literature. - UV-C LED technology reduced L. pneumophila levels by 3-log to 5-logs under simulated premise plumbing drinking water flow conditions. The results are promising but are highly dependent on the UV-C LED wavelength.