How can drinking water treatment plants serve as a more effective first line of defense against toxins from harmful algal blooms?

That’s what a team of researchers led by Dr. Soryong Chae of the University of Cincinnati, in collaboration with Dr. Jiyoung Lee of The Ohio State University, hoped to find out through recent research funded by the Ohio Department of Higher Education’s Harmful Algal Bloom Research Initiative (HABRI).

Now, with the project concluded, Chae’s team has created guidelines to share with water treatment plant operators to help improve the removal of harmful cyanotoxins based on different environmental conditions.

“Harmful algal blooms are not unusual anymore, they’re an annual, continuing event,” said Chae, an associate professor of chemical and environmental engineering at UC. “So this is a very important issue for us to think about how we can guarantee the safety of drinking water for the general public.”

In recent decades, scientists have observed a notable increase in cyanobacterial harmful algal blooms, or cHABs, occurring in Ohio’s freshwater bodies. Under certain conditions, cyanobacteria — also known as blue-green algae — can release toxins into the water, posing risks to public health and aquatic ecosystems.

To remove contaminants from the water, treatment facilities often use a series of steps called coagulation, flocculation, and sedimentation (CFS). Through this method, engineers use chemicals to force particles suspended in water to join together in large masses or “chunks” that can be settled down using gravity.

However, with cyanobacteria, the physical and chemical processes involved can potentially disrupt cells and cause more toxins to be released, raising significant concerns for water treatment plant operators. What’s important to understand in this regard, Chae said, is that cyanobacteria are living organisms.

“We shouldn’t treat them as chemicals, we should treat them as living things,” he said. “That’s the most important lesson I learned. They depend on the environment, temperature, and water chemistry.”

Cyanobacteria are very diverse in terms of their shape, surface properties, and what toxins they produce under certain conditions, Chae said. How these microorganisms react to chemical treatments also varies widely, he said.

“Our study can provide some guidance, that maybe you need to use this chemical with a certain dose, mixing speed, and sedimentation time by gravity. They can tune their treatment plan to achieve a certain level of removal.”
Dr. Soryong Chae

“This is a very tricky question for scientists: why do we have this specific toxin in the water this year, and not last year?” Chae said. “It’s a very important thing to understand.”

Through the project, researchers aimed to uncover how site-specific environmental factors and water chemistry affect cyanobacteria and their removal from drinking water sources through CFS.

To accomplish this, Chae’s team collected samples of water from Lake Erie and Grand Lake St. Marys on a bi-monthly basis. Some samples were sent to Lee’s lab at The Ohio State University’s College of Public Health to characterize cyanobacteria species and toxins. Meanwhile, at Chae’s lab at UC, researchers used the samples to conduct water quality tests before and after CFS treatments.

Researchers worked to provide a biological context for the treated source water, using DNA analysis to detect cyanobacterial genes and examine the full microbial communities present in the water collected. Ultimately, they observed potential decreases in cyanobacterial genes and toxins following various CFS treatments.

Using their findings, Chae’s team developed guidelines for drinking water treatment plants. The information will be open source and made publicly available on a website later on.

“We tried to provide guidelines for how the operators can maximize their efficiency in understanding these changes over time and in different places,” Chae said. “Those optimization processes were not available before.”

“Let’s say some plant in Toledo has a specific microorganism blooming for the summer, and they’re struggling to remove those cyanobacteria from the water,” he continued. “Our study can provide some guidance, that maybe you need to use this chemical with a certain dose, mixing speed, and sedimentation time by gravity. They can tune their treatment plan to achieve a certain level of removal.”

By following these guidelines, treatment plants can remove cyanobacteria at the beginning of the treatment process without releasing toxins into the water, Chae said, thereby improving water quality and safeguarding public health. This approach could be expanded to any state in the country, or even outside the U.S., he said.

“Hopefully this effort can lead to some larger-scale network that considers the nature of cyanobacteria and cyanotoxins and how we mitigate the risk at the plant operator level,” Chae said.

Notably, the outcomes of the project served as a foundation for a new 10-year research project awarded by the National Science Foundation as part of a $160 million initiative to protect water quality in the Great Lakes.

In addition, Chae said that most of the students involved in the two-year project have gained employment from public utilities in Ohio thanks to their experience studying water treatment processes.

“This was a great opportunity for them to address a real problem in our daily lives,” he said.

For more information about Dr. Chae’s HABRI research, contact him at chaesg@ucmail.uc.edu.

Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.