‘While the term ‘bypass’ can sound concerning, it does not mean that raw sewage is being discharged,’ a city official said
Sault Ste. Marie’s twin cities received roughly 30 mm of rain overnight into Tuesday morning, enough to cause water treatment plants on both sides of the river to bypass some of their treatment processes.
This means that for a few hours, the water released into the St. Marys River was not as treated as it usually is.
On the Ontario side, the city was forced to use a bypass for roughly two hours – from 12:55 until 3:01 a.m.
For the American side, the city used a bypass from 1 a.m. until roughly 5:25 a.m.
Andrew Mallette, manager of development and environmental engineering with the City of Sault Ste. Marie in Ontario, said a bypass at a wastewater treatment facility is not a failure of the system.
It’s “a controlled design feature that allows the facility to manage high flows, such as during periods of heavy rain. While the term ‘bypass’ can sound concerning, it does not mean that raw sewage is being discharged.”
Wastewater goes through key treatment steps that include screening and grit removal, primary treatment (settling), secondary treatment (aeration and clarification), and disinfection.
“In most instances, bypass only means that the secondary treatment is bypassed,” Mallette said.
“However, the remaining treatment stages can handle flows more than double what secondary treatment can handle,” he said.
This process is common in municipalities and ensures that wastewater continues to receive significant treatment before being discharged.
The City of Sault Ste. Marie owns the property and assets to ensure essential service is provided to the community. Operations are contracted to PUC, and the Ministry of the Environment, Conservation and Parks is the compliance authority.
“Bypasses are controlled and expected as part of wastewater management. They are regulated and monitored to ensure waterway protection,” Mallette said.
Sault Ste. Marie did not break any records for rainfall this week. For Sept. 22, the record of 41.9 mm of rain was set in 1959, said Steven Flisfeder, a meteorologist with Environment Canada.
Although Chapleau received 91.7 mm of rain on Monday and Tuesday, a representative said the township’s water treatment plant did not need to use a bypass.
In 2012, the City of Thunder Bay received enough rainwater to put its water treatment plant out of commission for several days starting on May 28. Over a period of roughly 36 hours, some areas in and around the city received up to 108 mm of rain.