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Municipal waste water treatment plant in Montreal, Canada

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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Municipal waste water treatment plant in Montreal, Canada

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  1. Municipal waste water treatment plant in Montreal, Canada Prepared by Guillaume Fournier

  2. 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.

  3. 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.

  4. Map of the sewage system in Montreal

  5. How does the plant works? • Pumping • Bar screening • Sand removal • Settling tanks • Sludge processing: storing, homogenisation, conditioning, dewatering, incineration

  6. 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.

  7. 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!

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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%

  13. 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.

  14. 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.

  15. 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)

  16. 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!

  17. Pumping station

  18. Residues of the mechanical screening

  19. Sand removal

  20. Settling tank

  21. Filter-press

  22. QUESTIONS, COMMENTS? Thank you

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