UV LED photolysis system for chloramine and free chlorine removal in drinking water
A compact, mercury-free LED device that uses targeted ultraviolet wavelengths to photolyze chloramines (mono-, di-, and tri-chloramine) and free chlorine into harmless byproducts while providing secondary disinfection. Designed for drinking water utilities seeking safer, more sustainable alternatives to traditional chloramine management.
Overview
Chloramines are widely used as secondary disinfectants in drinking water distribution systems, but they can degrade water quality, form odor-causing compounds, and harm aquatic life when discharged. This solution leverages ultraviolet light-emitting diodes (UV LEDs) tuned to wavelengths that match the peak absorption spectra of chloramine species, enabling rapid photolysis (light-driven chemical breakdown) into nitrogen gas and chloride ions. The approach eliminates the need for chemical quenching agents, avoids the environmental hazards of mercury-based UV lamps, and simultaneously delivers secondary disinfection of microorganisms.
Technical specifications
Core technology:
- UV LEDs emitting at specific wavelengths (220–320 nm) selected to match the molar absorptivity peaks of target chloramine species
- Monochloramine (NH2Cl) peak absorbance at 245 nm with high molar absorptivity (Emax = 455)
- Di- and tri-chloramine and free chlorine species absorb between 220–340 nm with Emax > 100
- Mercury-free LED design with instant on/off capability and operational lifespan exceeding 5 years
Validated performance:
- NH2Cl concentrations of 5–25 mgCl2/L reduced to below 0.1 mgCl2/L under 285 nm LED exposure
- Faster decay rates observed at 265 nm compared to 285 nm, consistent with proximity to the 245 nm absorption peak
- Byproducts are nitrogen gas and chloride ions, both innocuous in drinking water
Planned device specifications:
- Compact flow-through enclosure (less than 4" x 4" x 4")
- Designed flow rate of 1.5 L/min
- Targeted removal of chloramines from 10 mgCl2/L to below 0.1 mgCl2/L
- Five LED wavelength options (220–320 nm) for species-specific optimization
Technology readiness level
The technology is currently at TRL 3–4 (analytical and experimental proof-of-concept), with batch experiments completed demonstrating rapid chloramine photolysis. The research team brings 25+ years of experience in water disinfection chemistry. Near-term validation activities include determining quantum yields (molecules degraded per photon absorbed) and reaction rates across five LED wavelengths in ultrapure and simulated tap water at pH 5–10, followed by fabrication and testing of a compact flow-through device. This solution is well-suited for drinking water utilities, point-of-entry treatment systems, and industrial water applications requiring chloramine residual management.
About Arizona State University
Arizona State University is a comprehensive public research university with a multi-campus presence across the Phoenix metropolitan area and a scale that supports interdisciplinary, use-inspired discovery. Industry partners access co-located laboratories, a research and technology park, and innovation centers that house corporate teams with faculty to speed prototyping and validation. A formal alliance with a major hospital system and proximity to a fast-growing manufacturing corridor enable clinical translation and pilot-scale testbeds, while applied student engagements create dependable talent pipelines. Research is backed by competitive federal funding from agencies such as NSF, NIH, DOE, DOD, and NASA. A dedicated technology transfer office supports IP, licensing, and startup formation.
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