Does Waste Affect Drinking Water?

Guest Post By: Lake Ontario Waterkeeper


Canadians are extremely fortunate to have their drinking water come from one of the largest fresh water supplies in the world - the Great Lakes. And in Toronto, the drinking supply comes from Lake Ontario. In fact, the body of the average adult is 60% Lake Ontario (more if you’re a kid)!


The topic of sewage bypasses, and combined sewer overflows in Toronto has caused passionate debates. And after plumes of brown water were spotted in Lake Ontario following heavy rainfall, people were concerned that their source of drinking water was being compromised. 


The answer is Yes. All pollution “affects” Lake Ontario, in the sense that the lake provides drinking water for millions of people. Everything we put in the lake must be filtered out again before water is suitable for drinking. So everything from flushing a non-flushable wipe down the toilet to throwing your garbage from your lunch at the beach on the ground affects the lake. Even if you aren’t directly putting anything in the lake, it can still ultimately end up in the water. 


What most people are really asking is whether bypasses, overflows, and stormwater pose a risk to their health. 

The City of Toronto says no. According to the City, the placement of intake pipes minimizes the potential for events such as sewage bypasses to adversely affect finished water quality. The City also notes that water also goes through a rigorous testing and filtration process before it reaches your tap. It tests water samples every 4 hours and more thoroughly than required by the Ministry of the Environment’s Ontario Drinking Water Standards. 



However, Environment Canada does identify wastewater effluents as a threat to drinking water sources. And there have been a few isolated incidents in Canada where drinking water was contaminated by sewer overflows, stormwater and partially treated wastewater from treatment plants. 


Emerging issues raise concerns about the quality of our drinking water in future. One example is the increasing presence of pharmaceuticals in our drinking water supply. When Health Canada sampled tap water across Canada, researchers found traces of acetaminophen, codeine, antibiotics, hormones, steroids, and antiepileptic compounds, and dozens of other chemicals. Most treatment plants cannot filter out pharmaceuticals.


The bottom line is, our water treatment plants need to be updated, in order to prevent waste, sewage bypasses and pharmaceuticals from impacting our drinking water quality and negatively impacting the environment. But we also play a large part in the health of the lake, and how waste ends up in it. So the next time you flush or simply discard trash, think about the impact it can have on the water we love so much. 

Lake Ontario Waterkeeper is a Canadian charity working for a day when every person in our watershed can safely touch the water, when the water is pure enough to drink, and when the lake is clean and wild enough that you could toss in a line anywhere and pull out a fish. For more information visit

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