Casselman starts chlorine dioxide oxidation pilot to solve water’s manganese issue

manganese discoloration
During summer 2023, Casselman’s manganese levels often averaged between 0.35 mg/L. and 0.45 mg/L and even reached 1 mg/L in late July. This created a yellowish-brown hue in the water. Stock Photo Credit: Andriy Medvediuk,

The Ontario Town of Casselman is planning to move forward with a chlorine dioxide oxidation pilot project to address rising levels of manganese in the South Nation River turning the community’s tap water yellowish brown. But local leaders say there will be many hoops of approval to jump through as the province wades through the technology’s unfamiliar waters. 

In February, the town council extended its consulting agreement with Bill Dallala, a senior chemical engineer and water treatment expert with Montreal-based Krypton Scien-tek Inc., until summer 2024.     

Studying Casselman’s manganese challenges in fall of 2023, Dallala recommended that the town discontinue its use of chlorine gas and ammonium sulfate and rely instead on chlorine dioxide as a powerful disinfectant. 

“The most powerful advantage of chlorine dioxide is that it’s much faster to oxidize the manganese or the iron and reduce turbidity levels in the water, and finally, does not react with carbon to generate THM [trihalomethanes] like chlorine,” states Dallala’s 2023 report. 

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Manganese is an essential element for humans that occurs naturally in the environment and is widely distributed in air, water and soil. Health Canada’s maximum acceptable concentration for total manganese in drinking water is 0.12 mg/L. During summer 2023, Casselman’s levels often averaged between 0.35 mg/L. and 0.45 mg/L and even reached 1 mg/L in late July. 

Casselman’s water remains safe to drink, despite the discoloration. But Dallala’s report adds that Casselman, located just southeast of Ottawa, “must also abandon” its chloramination technology and discontinue use of potassium permanganate to resolve the lingering manganese issue, which has drawn complaints from residents.  

He also told Casselman officials that he needs help from engineers to provide detailed drawings. The “time-consuming process,” he said, will be helped through a collaboration with J.L. Richards & Associates Ltd., as well as the Ontario Clean Water Agency, the provincial authority that operates and maintains Casselman’s water and wastewater treatment facility. 

“Firstly, this is a completely new way to treat water in Ontario,” states a February public works update by Casselman staff on the water modification project. “Therefore, the [Ministry of Environment Conservation and Parks] does not have the expertise to provide feedback. The process to get the necessary approvals is long, as every step and action needs to be detailed quite elaborately to get the go ahead.” 

Casselman has received a $1 million federal grant to address manganese in its municipal water system. The municipality has also contributed $266,700.  

Casselman Mayor Geneviève Lajoie told residents that she hopes they will notice a positive difference in the colour of the town’s tap water by spring, as the water modification pilot project gets underway. However, Dallala pointed out that testing will be challenged by the fact that manganese levels are often low during the winter and even spring months. It typically presents more aggressively in the summertime, he said. 

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