Why UV LEDs are Important
According to the European Environment Agency Europe’s State of Water 2024 report, “water stress is already occurring in Europe. It affects 20% of Europe’s territory and 30% of the population every year.” The Agency warns that “Europe’s water is under significant pressure, presenting serious challenges to water security, now and in the future.” These pressures underline the urgency for effective technologies that deliver safe water and wastewater treatment with minimal environmental burden.
Across the Baltic region, utilities are searching for practical solutions to maintain effective microbial drinking water and wastewater treatment technologies as global restrictions phase out mercury mining, a key component in traditional ultraviolet (UV) disinfection. The Minamata Convention on Mercury and recent EU regulations will soon eliminate its use in industry, but most UV disinfection systems still depend on mercury-vapor lamps. Mercury metal is a potent neurotoxin that demands complex disposal and storage. For utilities, compliance has become both an environmental and financial burden. Countries across the Baltic region stand at a critical inflection point on how to achieve disinfection in the absence of traditional mercury UV systems.
Utilities across the Baltic region have long depended on mercury lamps because alternatives were unavailable. However, that is no longer the case, with the advances in solid-state light technology enabling UV LEDs to deliver the same level of disinfection without mercury, with the added potential to reduce energy consumption and greenhouse gas emissions. Our research team at Dalhousie University in Nova Scotia, Canada, in partnership with AquiSense Technologies, Halifax Water, and other North American Utility and industry partners, funded through a Water Research Foundation grant, recently demonstrated the world’s first municipal-scale UV LED reactor for wastewater treatment. The full-scale reactor, operating at 545 to 817 m3/day, achieved an average 3.2-log reduction of E. coli at a UV fluence of at least 30 mJ/cm2 and greater than a 3-log reduction in total coliforms, with delivered fluences between 28 and 148 mJ/cm2.
Conventional UV mercury lamps emit light and heat in all directions. In wastewater applications, heat can increase the rate of material buildup and fouling, leading to significant operational downtime and cleaning expenses. UV LEDs generate unidirectional light while dispersing heat backward, which results in minimal fouling, clear optics, and consistent delivery of UV light to the water column. This precision design produces targeted UV radiation that efficiently inactivates microorganisms while avoiding the high temperatures that promote fouling. Because LEDs emit photons in narrow wavelength bands, their disinfection performance can be optimized to match the DNA or RNA absorbance peaks of target microorganisms, enabling wavelength-specific inactivation and improved fluence efficiency.
Our recent research has shown that this precision application of UV also has the ability to degrade contaminants of concern. In tests with six trace organic pollutants, UV LEDs tuned to 275 nm degraded estrogenic and aromatic compounds up to ten times more efficiently than medium-pressure mercury systems by aligning emission wavelengths with molecular absorbance profiles. This ability to tailor wavelength emission opens new possibilities for chemical-free treatment of pharmaceuticals, hormones, and other micropollutants. As LED technology continues to advance, these insights suggest a new era of cleaner, smarter water and wastewater treatment.
Alignment with Baltic Sustainability Goals
For the Baltic region, where water protection and renewable energy integration are shared policy goals, UV LEDs present a unique opportunity. They could operate at low voltage and can be directly powered by wind or solar energy without conversion losses. Because their intensity can be modulated electronically, these systems can align power consumption with renewable energy availability and treatment capacity requirements. This design also supports the HELCOM Baltic Sea Action Plan by reducing the need for chemical transport, storage, and emissions associated with traditional treatment. Each installation represents a step toward decarbonized infrastructure that connects energy efficiency with ecosystem protection.
The European Commission’s Water Resilience Strategy (2025) emphasizes that “reducing water abstraction and enhancing water efficiency should take priority over increasing supply”. Integrating low-energy UV LED systems directly supports this directive while advancing the EU’s target “to enhance water efficiency by at least 10% by 2030.” The EEA also highlights that “Europe is the world’s fastest-warming continent,” and about “30% of the EU’s land area experiences seasonal water scarcity annually.” For northern regions like the Baltic basin, where climate impacts are intensifying, water-smart technologies that reduce operational energy and leakage are vital.
The Future of Safe Water
The State of Water 2024 report calls for “up-to-date and timely information on water quantity and quality” to enable more equitable and sustainable water allocation.
The shift to UV LEDs is part of a broader modernization of how water quality is managed. As new treatment technologies are adopted, the way we design, monitor and evaluate treatment systems must evolve. Conventional microbial assays cannot capture wavelength-specific fluence or molecular-level impacts. Molecular tools such as quantitative PCR and next-generation sequencing now provide direct measures of viral and bacterial gene damage. As advancement progresses in treatment technologies (e.g., UV LEDs) and molecular detection methods (e.g., next-generation sequencing), it is essential that sampling frameworks and associated decision making evolves in parallel. Together these innovations can transform how utilities assess performance and risk in real time.
As LED technologies continue to improve, researchers are already looking toward the next step, where light sources are derived from heavy-metal free quantum dots to minimize toxic metal inputs and maximize light duration to improve sustainability. In practical terms, UV LED systems are already more sustainable than traditional mercury lamps and quantum LED (QLED) systems will advance treatment efficacy and sustainability. This next generation of UV technology builds directly on the success of today’s UV LEDs and shows how light-based treatment can continue to evolve toward cleaner and smarter water systems.
Graham A. Gagnon
Vice President Research & Innovation (Acting)
Professor & Director
Centre for Water Resources Studies, Department of Civil & Resource Engineering
Dalhousie University
Canada
Amina K. Stoddart
Associate Professor
Centre for Water Resources Studies, Department of Civil & Resource Engineering
Dalhousie University
Canada
Emalie K. Hayes
Post-Doctoral Researcher
Centre for Water Resources Studies, Department of Civil & Resource Engineering
Dalhousie University
Canada
Megan Fuller
Director of Indigenous Research
Centre for Water Resources Studies, Department of Civil & Resource Engineering
Dalhousie University
Canada
