Full-Scale UV-LED Validation with Organism-Specific Dose Determination

UV-LED technology, utilizing light-emitting diodes (LED) to produce UVC light, has been demonstrated as a promising technology for drinking water applications. The absence of a validated UV-LED reactor or a validation protocol may limit its application. The first full-scale UV-LED280 reactor in the Americas was installed at a municipal well for Legionella pneumophila disinfection. USEPA guidance was used to design validation bench- and full-scale tests with two surrogates (MS2 and T1UV). Full-scale parameters were varied over relevant ranges (893–1000 GPM, 90–99% UVT280, 12–100% power levels, and varying LED280 bank operation) to understand effects on performance. The Calculated Dose Approach successfully generated L. pneumophila-tailored UV intensity setpoints and a validated reduction equivalent dose (RED) monitoring equation. Validated L. pneumophila REDs of 3.7–47 mJ/cm2 were found through the incorporation of an L. pneumophila UV sensitivity factor in the equation, not only reducing RED over/underestimation but also removing the need for UVDGM bias factors. The UV-LED280 REDs exceeded the requirements under a variety of extreme conditions. Although this study successfully demonstrates a UV-LED280 reactor and validation approach, guidance specifically addressing UV-LED would provide clarity and assurance to utilities seeking to implement and receive treatment credit with this promising new technology.