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Niagara Region takes steps to protect drinking water from blue-green algae

August 30, 2021  By Ground Water Canada

Niagara Region, Ont. – Niagara Region has moved to daily testing, more frequent visual inspection and enhanced monitoring after identifying a small quantity of blue-green algae upstream in the reservoirs serving the DeCew Falls Water Treatment Plant in Ontario’s Niagara Region.

The blue-green algae was first observed on Aug. 20.

The Region said in a news release that microcystin, the neurotoxin released by blue-green algae, has not been detected during daily testing of the water leaving the plant over the last few days. Therefore, there is no risk to human health at this time. The blue green algae is being removed to minimize the risk of it multiplying.


Since Niagara Region first identified blue green algae upstream from the Decew Falls Water Treatment Plant intake in July 2016, the Region has enhanced monitoring for both blue-green algae and the microcystin toxin across all water treatment plants. This includes routine visual inspection of the intakes and reservoirs to all six water treatment plans, as well as weekly testing for microcystin in the water before and after treatment.

Over the past two weeks, very low levels of microcystin have been detected intermittently in all of Niagara’s water treatment plants. Fortunately, the concentrations of microcystin have all measured at less than two per cent of the amount permissible by the Ontario Drinking Water Standards. The water from all Region water treatment plants remains safe to drink.

After the first detection of microcystin, Niagara Region moved to daily testing, and further increased the frequency of visual inspection for blue-green algae. This allowed for identifying and rapidly responding to the blue-green algae at the Decew Falls Water Treatment Plant. Testing is slowly returning to a weekly frequency in locations where microcystin has been undetectable for several consecutive days and no blue-green algae has been seen. Water treatment processes have also been adjusted to neutralize and remove toxins before they enter the water distribution system.

The Region’s Public Health and Public Works departments are working with the Ministry of Environment, Conservation and Parks to monitor for and prevent any potential future risk to the public from blue-green algae.

Blue-green algae, known as cyanobacteria, can sometimes produce a toxin that is a risk to health. Blue-green algae occurs naturally in fresh water lakes, ponds, rivers and streams in late summer and early fall. Current warm weather has made blue-green algae more prevalent in many parts of North America, including in Lake Erie which indirectly feed Niagara’s water treatment plants.

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