The University of Toledo is testing a real-time optical sensor on Lake Erie drinking water to protect public drinking water during the harmful algal bloom season.
In what is believed to be the first use of real-time algae sensors in the U.S., a device known as PhycoSens samples the water coming into the Toledo Water Treatment Plant every 15 minutes, then uploads the measurement data online for researchers and water utility managers to access remotely.
The test deployment of the sensor system is part of a $1.4-million UToledo project funded by the U.S. Army Corps of Engineers that began more than a year ago and focuses on early detection and management of harmful algal blooms.
The investment follows the 2014 Toledo water crisis that left half a million residents without safe tap water for three days. Microcystin, a toxin caused by algal blooms, was detected in the water system.
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“Our work this summer with the PhycoSens device is the first test of this online algae monitoring system at a drinking water plant in the U.S.,” said Dr. Thomas Bridgeman, professor of ecology and director of the UToledo Lake Erie Center. “If we show success at the Toledo Water Treatment Plant and throughout the region to immediately detect and notify of toxin release, then it can be scaled up nationwide. So far, it’s showing great promise,” he added.
It’s not just the size and appearance of the algal bloom that matters, say the UToledo scientists, but what is happening in the cells. They say the biggest advantage of the real-time optical algae sensor is the ability to tell whether tiny single-celled organisms known as cyanobacteria, which cause harmful algal blooms in Lake Erie, are fragile and starting to break open. If the cells break open, they can release toxins into the water, the researchers say.
The sensors can provide a warning, but they do not provide actual toxin readings. Dissolved toxin is more challenging for water treatment plants to remove because it can pass through filters and must be removed by chemical treatment before water leaves the plant for public faucets, the researchers announced in a statement about the project.
“A large release of toxin can happen in a matter of hours, and it is critical for water plant operators to have this information so they can adjust their treatment levels quickly, before dissolved toxin can get through the plant,” said Bridgeman. “The data are produced every few minutes, which makes it a useful early warning tool for a potentially rapidly changing algal situation.”
So far, researchers have not detected cell breakage. They were, however, able to show the peak of the bloom and its decline through data collected in late July.
“However, UToledo crews on our research vessel taking water samples out in the lake throughout Lake Erie’s western basin — not near the water intake — have detected cell breakage using the manual version of the same device this season,” explained Bridgeman.
Jeff Martin, chief chemist at the Toledo Water Treatment Plant, said the sensors have been useful to gauge the severity of algae levels from Lake Erie; however, they were unable to have remote access to the data until part way through the bloom season due to computer issues.
The device, made by the German company bbe Moldaenke, will be removed from the water treatment plant for analysis in October, when the team will determine whether to put it back in the plant for observation next summer.
