Heavy rains and flooding from Tuesday’s record-breaking storm have led to 1300 megalitres of partially treated wastewater being released into Lake Ontario, according to CP24. To put it into perspective, this is about 1,300,000,000 liters.
A spokesperson told the outlet that three wastewater plants were “bypassing” (diverting water away from the treatment plants and discharging into the environment).
Severe rain has caused a bypass at #CityofTO Humber Treatment Plant. All wastewater is disinfected and treated per strict provincial and federal regulations. Learn more: https://t.co/9v9OzGgcFh pic.twitter.com/zu9PE2KmZT
— 311 Toronto (@311Toronto) July 16, 2024
According to the City of Toronto, the city’s wastewater treatment plants operate according to strict provincial and federal regulatory requirements, and all wastewater is disinfected even during a bypass event. When there’s heavy rain or snow melt, the increased volume of rainwater and sewage can be fully treated for some time, but if heavy rain continues, the volume of rainwater and sewage reaching a plant might be more than what can be treated in a short period of time.
“In this case, some of the wastewater may be diverted around the biological process (secondary treatment process) to protect the plant. This diversion around one process is called a “bypass”, the City stated. “The bypassed wastewater still goes through screening, grit removal, primary treatment, phosphorous removal and full disinfection to ensure the treated water always meets strict federal and provincial regulations.”
Health officials noted that it can be unsafe to swim, even at designated swimming beaches, for 48 hours after a rainfall due to the possible presence of high levels of bacteria that could pose a risk to human health.
“The bacteria could be a result from water pollution, which is a complex issue and can come from many sources,” the City noted on its website.
As of publication, six out of 10 supervised public beaches in Toronto are marked as “unsafe to swim” due to the E.coli counts in the beach water quality samples taken over the past 24 hours: Marie Curtis Park East Beach, Sunnyside Beach, Ward’s Island Beach, Woodbine Beaches, Kew Balmy Beach, and Bluffer’s Beach Park. Four are considered safe to swim: Hanlan’s Point Beach, Gibraltar Point Beach, Centre Island Beach, Cherry Beach.
Peel Region also advised against swimming along the shores of Lake Ontario in Mississauga after Tuesday’s flooding caused wastewater to overflow into the lake.
“Due to recent heavy rains and subsequent flooding, an overflow of partially treated wastewater from the G. E. Booth wastewater treatment facility has been released into Lake Ontario. The exact amount of water is unknown at this time,” the City noted as part of a series of posts on X on Tuesday. “Heavy rains can flush pollutants into water bodies. Residents are advised to refrain from swimming or engaging in any water-related activities along the Lake Ontario beaches in Mississauga until further notice.”
Due to recent heavy rains and subsequent flooding, an overflow of partially treated wastewater from the G. E. Booth wastewater treatment facility has been released into Lake Ontario.
The exact amount of water is unknown at this time.
— Peel Region (@regionofpeel) July 17, 2024
As of July 18, three beaches in Mississauga were considered unsafe for swimming (Jack Darling Memorial Park, Lakefront Promenade (A.E. Crookes Park), and Richard’s Memorial Park, while Professor’s Lake Beach is considered safe for swimming.
Environment Canada reported that 97.8 mm of rain fell in Toronto on Tuesday, surpassing the city’s July 16 rainfall record and ranking as one of the city’s top five daily rain events.
Tuesday’s flood led to power outages for tens of thousands of people, with major streets, highways, and TTC trains shutting down (there are even visuals of drivers abandoning their cars and kayaking across the city).
