Harmful algal blooms are becoming a bigger problem for drinking water systems, and traditional treatment methods are struggling to keep up. Cyanobacteria outbreaks, fueled by nutrient pollution and climate change, can lead to dangerous toxin levels in water supplies. When these algae die off, they release cyanotoxins that are harmful to both humans and animals. Standard filtration and boiling offer no protection, and chlorine alone is not always effective.
Researchers at the University of Cincinnati have been testing a new approach that could significantly improve toxin removal. By combining ultraviolet (UV) light with chlorine, they found a way to break down cyanotoxins more efficiently while keeping chemical demand and energy consumption low. The method showed promising results in laboratory experiments, reducing toxin levels to within World Health Organization safety limits without producing harmful disinfection byproducts.
A Growing Challenge for Water Utilities
Cyanobacteria thrive in nutrient-rich waters, often due to agricultural runoff, wastewater discharge, and storm-related sediment disturbances. Under the right conditions, these bacteria multiply rapidly, forming blooms that can cover large portions of lakes and reservoirs. When the blooms die off, they release toxins such as microcystins, which can persist in water for weeks or even months.
These toxins have caused serious public health concerns. In 2014, nearly half a million residents in Toledo, Ohio, were left without safe drinking water after a cyanotoxin outbreak contaminated the city’s supply. In other cases, such as in Clear Lake, California, and Lake Okeechobee, Florida, cyanotoxin levels have been measured at more than 100 times the federally allowed limits. Incidents like these highlight the urgent need for better treatment solutions.
Chlorine is widely used for disinfection, but it is not always effective at breaking down cyanotoxins on its own. The University of Cincinnati researchers set out to find a more efficient way to eliminate these harmful compounds.
How UV and Chlorine Work Together
The study found that the combination of UV radiation and chlorination produced significantly better results than chlorine alone. The UV light helped break down toxin molecules, making them more susceptible to oxidation. Chlorine then completed the process by degrading the weakened toxins.
Another key finding was the role of chloride ions naturally present in the water. These ions helped form reactive molecular chlorine, which further enhanced the breakdown of toxins. This process not only improved treatment efficiency but also helped keep chemical and energy use at manageable levels.
Potential for Full-Scale Implementation
For water treatment utilities, this research presents a promising alternative to traditional cyanotoxin treatment methods. The combination of UV and chlorine offers a cost-effective and scalable option that improves efficiency without introducing new risks. Municipalities struggling with harmful algal blooms could benefit from adopting this approach, especially as bloom frequency continues to rise.
Before utilities can widely implement this method, further testing is needed on a larger scale. Pilot studies in real-world water treatment settings will be necessary to confirm the effectiveness seen in laboratory experiments. Additionally, regulatory agencies may need to establish guidelines for integrating this approach into existing treatment frameworks.
A Lasting Impact
With harmful algal blooms becoming a more frequent threat, the need for better treatment methods is more urgent than ever. The combination of UV light and chlorine could be a major step forward in protecting drinking water supplies from cyanotoxins. Water utilities should be watching closely as further studies explore the full potential of this approach.
SOURCES: Environmental Science & Technology, Smart Water Magazine
