The world's biggest cesspool

>> >> The good, the bad and the smelly down at the MUC sewage treatment plant

by PHILIP PREVILLE

Ever wonder where the water goes when you flush? It goes to the Montreal Urban Community's wastewater treatment plant in the east end. A massive, sprawling complex built at a cost of $1.3 billion, Montreal's plant is the biggest in the world. Resembling a large industrial digestive tract, the plant could even be considered an engineering marvel--except for the fact that, in the minds of some environmentalists, it actually doesn't work very well.



Step 1: Collect the wastewater. Almost every toilet, drain and rain collector on the island is connected to the underground network that leads to the plant's pumping station. The wastewater travels there simply by force of gravity, where it is collected in four cylindrical concrete tanks (each 15 storeys deep) and pumped back up to the surface for treatment. Problem: Not every toilet is properly hooked up. "There are areas where developers have illegally hooked up their drainage systems to the storm sewers, which flow directly into the river," says Daniel Green of Société pour vaincre la pollution (SVP).



Step 2: Remove all the chunky stuff. By the time your shit gets to the plant, it's been travelling underground for dozens of kilometres and is pretty much fully dissolved. But everything that's been shoved down a sewer grate is filtered out, dried and sent to a landfill. This reporter spotted condoms, Naya bottles and a tennis ball while touring the facility. Problem: When the spring rains come, all the crushed rock (spread on roads and sidewalks throughout the winter) clogs up the system. High-pressure hoses are used to clear the blockage.



Step 3: Get the toxins to settle out. The now-filtered wastewater is directed to large settling pools, where it is injected with a coagulant and left to sit for up to six hours. The coagulant helps settle out all the heavy metals and other suspended solids. This coagulated crap, known as sludge (yes, "sludge" is a technical term), is then separated for disposal, while the water is washed out to the river. Problem: At best, the system captures about 60 per cent of the heavy metals. "It's impossible to get everything out unless you're willing to spend hundreds of millions more," says plant engineer Luc Tremblay. "As it stands, our effluent harms the river for a stretch of four or five kilometres, but that's better than killing 20 or 30 kilometres of river."



Step 4: Dispose of the sludge. At this point, the sludge is still mostly water. A series of drying techniques turn the sludge into "cakes," which are then transported via conveyor belt to either an incinerator, where it is burned, or to the biggest tumble-dryer you've ever seen, where it is dried into pellets and used as fertilizer. Problem: Says Tremblay: "We know our fertilizer contains too much cadmium, so we're careful not to re-introduce it into the food chain." Says Green: "Instead, they spread it on city parks in the east end, where children and dogs roll in the grass."



Final factoid: Through this entire process, the wastewater is never disinfected--which is to say, the fecal coliform bacteria in people's shit is never killed, and just washed out into the river. Possible solutions include adding a final treatment process with chlorine, hydrogen peroxide or UV rays. But all would cost at least $50 million to implement, which is more than the treatment plant's $43-million annual budget. :