Collaborative Research: Treatment of Cyanotoxins by UV/Chlorine: Optimizing Removal While Developing Strategies to Minimize Disinfection Byproducts and Toxicity

Harmful algal blooms (HABs) occur when harmful algae grow out of control in surface water systems including lakes, rivers, and estuaries. This causes a large decrease in oxygen levels in the water and the release of toxic chemicals commonly referred to as cyanotoxins. These toxins can cause illness and death in fish, animals, and humans.

HABs are increasing in frequency and severity throughout the world and are often triggered by excessive nutrients (phosphorus and nitrogen). In recent years, severe HABs have occurred in more than 20 states throughout the United States. However, traditional drinking water treatment processes (coagulation, flocculation, sedimentation, and chlorination) cannot fully remove cyanotoxins (to below the concentrations considered as toxic by federal and state agencies) especially during massive HAB events.

The overarching goal of this collaborative research project is to evaluate and optimize the performance of a new water treatment process that combines UV light with chlorine (UV/chlorine) to break down cyanotoxins present in drinking water. The successful completion of this project will benefit society through the development of new fundamental knowledge that could lead to a new water treatment technology (UV/Chlorine) for the removal cyanotoxins to safe levels while minimizing the formation of toxic disinfection by-products (DBPs).

Further benefits to society will be achieved through outreach and educational activities including 1) workshops and interactions with drinking water treatment professionals and relevant stakeholders, 2) course development, and 3) the mentoring of three doctoral students.

Cyanotoxins, released by cyanobacteria during harmful algae blooms (HABs), are major threats to human and ecosystem health in the United Stated and worldwide. Various water treatment technologies, including sorption with granular activated carbon, membrane filtration, chlorination, ozonation, and advanced oxidation processes (AOPs), have shown potential to remove or degrade cyanotoxins.

However, cellular lysis can occur during treatment thus increasing exposure to toxins from treated drinking water. In addition, toxic disinfection by-products (DBPs) might be generated when disinfectants such as chlorine react with cyanotoxins and/or algal/planktonic organic matter. Thus, a detailed and careful examination of cyanotoxin degradation during water treatment is critically needed to ensure safe drinking water for the public.

The overarching goals of this project are to evaluate the performance of UV/chlorine treatment to degrade cyanotoxins in drinking water sources and elucidate the mechanisms of DBP formation and toxicity under relevant process and environmental conditions. To advance these goals, the collaborative research team proposes to 1) investigate the degradation of two common classes of cyanotoxins (microcystins and cylindrospermopsin) along with a group of 70 related DBPs (including regulated and priority unregulated DBPs); 2) evaluate the role of process conditions (i.e., radiation dose and wavelength, chlorine dose) and water quality parameters (algal organic matter, presence of halides, and solution pH) on degradation efficiency, and 3) determine the reaction kinetics, formation pathways of transformation products including DBPs, and their potential toxicity to human and ecosystems using transcriptomics.

The successful completion of this project has potential for transformative impact through the development of new fundamental knowledge about the UV/Chlorine water treatment process that could lead to the effective removal cyanotoxins from drinking water sources to safe levels while minimizing the formation of toxic DBPs.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.