Advanced Algae Sensor Tested in Toledo Proves Valuable Tool in Protecting Drinking Water

An advanced technology tested in Toledo's water treatment system nearly two years ago could prove valuable in efforts to protect the water that flows from taps far beyond northwest Ohio, according to a study published by the University of Toledo.

UToledo scientists installed a real-time algae sensor at the Toledo Pumping Station in eastern Lucas County in 2022 as part of a broader initiative to detect and control harmful algal blooms early, sponsored by the U.S. Army Corps of Engineers. With the installation, the facility became known as the first in the country to test the fluorescence-based technology that detects a pigment that scientists believed could indicate the release of toxins from blue-green algae cells.

Dr. Thomas Bridgeman, professor of ecology and director of the UToledo Lake Erie Center (right), and Dr. Kuo-Pei Tsai, a postdoctoral fellow, read data from the online algae monitoring system tested in 2022 at Toledo's low-service pumping station in eastern Lucas County.

In a study recently published in the journal Science of the Total Environment, analysis of the data obtained confirms that the technology worked as intended.

“The device can detect cell lysis of blue-green algae in real time, providing early warning of potentially elevated levels of the microcystin toxin in the raw water,” said Dr. Kuo-Pei Tsai, lead author of the paper and a postdoctoral fellow at the UToledo Lake Erie Center. “This means that if another disaster like the one in 2014 were to occur, water treatment plant personnel could take immediate precautions.”

Scientists now have sufficient resources to detect and monitor harmful algal blooms. In Lake Erie, they are caused by cyanobacteria, also known as blue-green algae. Harmful algal blooms have been the focus of particularly intensive research since the water crisis in Toledo in 2014, when half a million residents were without clean tap water for three days.

To make matters worse for water plant operators, however, harmful algal blooms are not always harmful. In most cases, intact cyanobacterial cells, along with their toxins, can be easily filtered out of incoming water. However, when the cells begin to break down, their toxins are released into the water, requiring operators to use chemical treatments to absorb or destroy the toxins.

The degradation process is called lysis. It can be caused by outbreaks of naturally occurring viruses in the environment called cyanophages, as scientists say happened during the 2014 water crisis, or by the use of algaecides or water treatment chemicals. When cyanophages attack a fungal bloom, large amounts of poison can be released in a matter of hours.

Until now, water treatment plant operators have relied on relatively slow and expensive tests to directly monitor both cell-bound and free toxin levels in the water. The PhycoSens device, manufactured by German company bbe Moldaenke and installed at the UToledo Lake Erie Center pumping station, complements but does not replace these tests by detecting in real time a byproduct of cyanobacterial lysis: a pigment called unbound phycocyanin.

The scientists suspected that the detection of the pigment was an indication that the cyanobacteria's cell membranes were breaking down and possibly releasing microcystin. In addition, the instrument's reports on water samples taken every 15 minutes during the harmful algal bloom would alert operators to take immediate action.

“The device will allow water treatment plant operators to identify when the condition of a harmful algal bloom in their source water is rapidly changing and respond accordingly,” said Dr. Thomas Bridgeman, professor of ecology and director of the UToledo Lake Erie Center and lead author of the research article. “Without real-time data like this, the conservative approach may be to over-treat water with chemicals to ensure safety, which adds additional costs and can affect the taste of the water. Using this technology, treatment plant operators can better tailor their actions to the severity of the situation, saving money and improving taste while maintaining a high level of safety.”

Phyco-Sens collected samples between mid-July and mid-October 2022, providing researchers with a huge dataset to analyze. Additional laboratory studies using cyanobacteria, treatment chemicals and cyanophages led them to conclude that the presence of unbound phycocyanin is indeed a useful indicator of the onset of cyanobacterial cell lysis and thus the possible release of microcystin.

The purchase and installation of the device and related research are funded by a $1.4 million grant to the U.S. Army Corps of Engineers to develop improved technology for the early detection and control of harmful algal blooms.

Dr. Youngwoo Seo, professor in the Department of Civil and Environmental Engineering and Chemical Engineering, is leading the three-year project, which began in 2021. Dr. Dae-Wook Kang, assistant professor in the same department, is joining Bridgeman as co-investigator.

The researchers and their collaborators are working with municipal drinking water treatment plants in Bowling Green, Celina and Oregon, as well as in Toledo, where the Phyco-Sens is being used again this year, collecting samples in advance of harmful algal blooms.

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