Image copyright Twitter

On Wednesday, Montreal started dumping billions of litres of raw sewage into the city's main river, the St Lawrence.

It is a scheme that officials in Canada's second largest city say is necessary as they replace old infrastructure in the sewage treatment system.

They say the waste will be quickly diluted, but have advised people not to touch the water while the dump takes place.

The people of Montreal are also being asked not to flush medication, condoms or tampons down the toilet while the operation goes on.

In all, some 8bn litres (2.1bn gallons) will be released.

For context, that is roughly the equivalent to 14bn of these:

Image copyright PA

Or to 3,200 Olympic swimming pools:

Image copyright Getty Images

And if the St Lawrence river flowed over Niagara Falls, which it definitely doesn't, it would take all the sewage 47 minutes to travel over - more than 2.8m litres of water pass over all the falls in Niagara every second.

Image copyright Getty Images Image caption Repeat: Niagara Falls is nowhere near the St Lawrence river and the sewage

As we said, that is a lot of sewage.

Officials in Montreal say the dump will have little effect on the fish population and will not affect the quality of drinking water for citizens. And, so far, there are no reports of questionable smells.

But it's fair to say the city's residents are not especially happy.

The term #flushgate has been trending in Montreal for the past day, alongside subjects as diverse as Justin Bieber's new album and Condon (nothing to do with items in the river, he's a Montreal Canadiens ice hockey player).

This being Quebec province, the French term - #EauxUsées (wastewater) - is also proving popular. And, like any good scandal, it's given people a chance to practice their photo editing skills:

Image copyright Twitter Image caption 'Drastic solutions are being put in place in Quebec', one Twitter user wrote

The French-language Journal de Montreal had some fun too:

Image copyright Twitter

And it wouldn't be a real scandal if people did not respond by writing passive-aggressive graffiti:

Image copyright Twitter Image caption 'Fishing prohibited' - 'There are no fish left - they've all gone far away from all the pollution'

While the city says the sewage dump will not affect drinking water, there are concerns among the city's residents. But one user pointed out that such worries about drinking water are not new to some people in Canada: