Municipal waste water treatment plant in montreal canada
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Municipal waste water treatment plant in Montreal, Canada. Prepared by Guillaume Fournier. Montreal . Second biggest city in Canada (1.6 million inhabitants) Home to one of the biggest waste water treatment plant in North America.

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Montreal
Montreal

  • Second biggest city in Canada (1.6 million inhabitants)

  • Home to one of the biggest waste water treatment plant in North America.

  • Montreal being an island, before 1984, all sewage were going straight in surrounding rivers.


Rivi re des prairies waste water treatment plant
Rivière des prairies waste water treatment plant

  • Situated on the extreme eastern part of the island of Montreal.

  • Cleans 95% of Montreal sewage

  • Took from 1976 to 1998 to construct the sewage system and the plant to it’s final form.

  • Cost: 1.375 billions $ cad (0.87 billions euros)

  • Average flow of waste water coming in the station: 2 500 000 cubic meters/day. When raining, it goes up to 7 600 000 cubic meters/day.



How does the plant works
How does the plant works?

  • Pumping

  • Bar screening

  • Sand removal

  • Settling tanks

  • Sludge processing: storing, homogenisation, conditioning, dewatering, incineration


Pumping
Pumping

  • First operation within the waste water plant.

  • Can pump 88 cubic meter of waste water per second.

  • 17 pumps for a total power of 2500 to 5150 horsepower depending on the flow of waste water. Gets the water to the surface in channels.


Bar screening
Bar screening

  • The water is pumped to 2 channels. Coagulant is added before the screening.

  • Only the biggest residues are stopped in the screens (2.5cm and more).

  • There are 8 bar screens that are 4.6m in height.

  • Mechanical rakes get the sludge out.

  • What happens to the sludge ? See on next slide!


Sludge from bar screening
Sludge from bar screening

  • Transported by conveyor to the dewatering processing.

  • Dewatered by 2 drum presses to reduce the volume and humidity of the sludge.

  • Sludge is sent to landfill.

  • 2 tons and a half of sludge is sent everyday.


Sand removal
Sand removal

  • Sand sedimentation in continual chamber trap.

  • 14 channels of 68 meters X 7 meters X 4 meters.

  • Water is slowed down so the sedimentation takes maximum 10 minutes.

  • Sand is pumped to trucks that goes to landfill.

  • 14 tons of sand is pulled out of the water everyday.


Settling tanks
Settling tanks

  • 21 rectangular settling tanks (30X90 meters).

  • Floculant is added at the entrance of the tank (FeCl, Alun) to help sedimentation.

  • Water has to sediment during 2 hours to get a good quality

  • Rakes collect the top layer and bottom layer of sludge and push them into pumps.

  • Water is ready to go back into the river; the sludge is sent to the sludge treatment part.


Sludge processing storing
Sludge processing: storing

  • 4 reservoirs of 5000 cubic meters.

  • Air is pumped constantly into the sludge to keep it easier to process.

  • The gases that go out are processed by sodium hypochlorite before behing released into the atmosphere.


Sludge processing homogenisation and conditioning
Sludge processing: homogenisation and conditioning

  • Sludge is then processed to 5 tanks with agitators to keep it homogenised

  • It is then conditioned with cationic particules that favorise the separation of solid and liquid particules

  • Solid concentration: 3.5%


Sludge processing dewatering and incineration
Sludge processing: dewatering and incineration

  • 10 filter-press gets the water out of the sludge; gets the sludge to about 32% of solid particules. The sludge is now called a ‘cake’.

  • Cakes are principally processed to the 4 incinerator, total capacity of incineration of 400 tons per day. Ashes are dumped into trucks and transported to the landfill.

  • The heat emitted by the incinerator is used to heat the different buildings of the waste water treatment plant.


Sludge processing overflow of humid cakes
Sludge processing: overflow of humid cakes ?

  • 2 silos of 250 tons can process the overflow of humid cakes in case of huge melts of snow or big rains.

  • They can be then processed to 2 other drying unit that can make the cakes up to 92% of solids.


Performance
Performance

  • In Canada, there are no regulations of the BOD / COD of treated water. Still, in 2006, the BOD and COD were reduced of 40% in average.

  • Fecal matters reduced by 48%.

  • Respects 100% of all MAMR norms (Quebec Minister of Municipals Affairs)


Impact on the environment
Impact on the environment

  • Before 1986, more then 500 metric tonnes of dry sludge were thrown directly in the surrounding rivers per day. Nowadays, less then 50 tonnes per day.

  • Before the plant, more then 5.6 tonnes of phosphorus per day were going directly in the rivers. Now it is less then 1.3 tonnes per day.

  • Regeneration of St-Lawrence River and Rivière des Prairies from a completely polluted state to being able to swim in the water without any dangers.

  • PICTURE TIME!








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