We will assess the potential that algal toxin–degrading bacteria have to degrade toxins from water treatment facilities.

Why We Care
Harmful algal blooms (HABs) occur in eutrophic waters across the world and are characterized by large aggregations of naturally occurring photosynthetic bacteria that release cyanotoxins. A variety of cyanobacteria, including Microcystis and Planktothrix, are known to release microcystins, which threaten human health. Lake Erie, in particular, has been plagued by decades of large and toxic HABs that have fouled drinking water and negatively affected recreational activities, leading to anoxic and hypoxic conditions that kill fish and other wildlife. The three-day drinking water ban in Toledo, Ohio, in August 2014 presented a serious public health crisis for nearly 500,000 residents in northwest Ohio. This event drew national and international attention on Lake Erie HABs and renewed debates about the ability of municipal water systems to produce safe drinking water. This was not the first time that Lake Erie HABs and their water-soluble toxins have threatened drinking water supplies—a 2011 record-breaking Lake Erie HAB resulted in microcystin concentrations 224-times above World Health Organization (WHO) guidelines, and a 2013 Lake Erie HAB resulted in a drinking water ban in a rural township near Toledo. These HAB events are neither random, rare, nor isolated events. Large and significant Lake Erie HABs in 2015, 2017, and 2019 continue to raise public concerns about the safety of drinking water supplies.

What We are Doing
The WHO has issued a microcystins provisional ingestion guideline limit of 1 μg/L (ppb), and in 2015 the U.S. EPA issued ten-day health advisory ingestion guidelines of 0.3 μg/L (ppb) for infants and young children and 1.6 μg/L (ppb) for all other ages. Municipal water treatment facilities have a number of treatment processes at their disposal to treat microcystin-contaminated waters, including chlorination, powdered activated charcoal, and ozonation. However, these treatment processes are expensive and generate waste products and byproducts that require additional treatment processes to mitigate. In previous studies, the researchers selected for and isolated microcystin-degrading bacteria from Lake Erie. In addition, the researchers demonstrated that these bacteria degraded microcystins into non-toxic fragments. Sand filters inoculated with these bacteria (i.e., biofilters) removed microcystins from contaminated water as it flowed through the biofilter. Given these findings, the objectives of this project are to:

1. 1. 1. Develop and test the ability of microcystin-degrading bacteria to function in microcytin detoxifying biofilters;
      2. Test the ability of microcystin-degrading bacteria to degrade microcystins from water treatment waste products;
      3. Use next-generation approaches to identify toxin degrading enzymes from these bacteria;
      4. Test the ability of toxin degrading enzymes to breakdown microcystins into non-toxic fragments.

Taken together, microcystin-degrading bacteria in biofilters and microcystin-degrading enzymes could reduce water treatment costs, provide safe alternatives to conventional water treatment processes, and provide point-of-use (i.e., small scale) water treatment methods to remove microcystins from contaminated water supplies.

Dr. Jason Huntley of the University of Toledo–Health Science Campus leads this project. Dr. Dragan Isailovic (University of Toledo-Health Science Campus) is the co-investigator. The project is funded through the NCCOS Prevention, Control, and Mitigation of Harmful Algal Blooms Program.