Boues municipales: tout dépend du traitement

Photo: Greg Agnew

Pendant que les gens de Halifax se plaignent de la senteur venant des boues municipales étendues sur les bords des routes, les gens de Moncton se mettent en ligne pour pouvoir s'en servir comme engrais.

En effet, Halifax prend les solides des égouts, les traite et les étends sur les bords des chemins, les considérants comme de l'engrais. Mais à Moncton, la municipalité a pris la chose en main (yeurk!). C'est la Greater Moncton Sewerage Commission qui voit aux procédés de traitement des boues municipales et peut se vanter de produire quelque chose de beaucoup plus acceptable.

À l'usine de traitement des eaux usées (égouts), les solides sont séparés des liquides et de la chaux est ajoutée aux solides pour stabiliser le produit, réduire les odeurs et faciliter le transport. La chaux devient aussi une partie intégrante de l'engrais en bout de ligne. Les solides sont ensuite compostés à un autre site où l'on ajoute de l'écorce et des feuilles et d'autres déchêts organiques verts: le tout est composté à 75 degrés Celsius pour tuer les pathogènes et les bactéries.

Il en résulte un compost qui contient environ 10% de boues municipales. Environ 2,000 résidents sont venus se servir et 3 municipalités s'en servent à différents endroits dans leur territoire. Le porte-parole dit que l'on produit environ 15,000 tonnes de compost par année et qu'il peut être utilisé dans les jardins potagers. Il attribue son succès au fait que la municipalité a gardé le contrôle du processus et n'a pas sous-contracté au privé.
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"Metro scoops up the poop

Haligonians have been kicking up a stink this week about the smell they say is coming from treated human waste the municipality used as fertilizer along roadways in one area of the city. The use of biosolids has not been well received by residents, to say the least.

Zoom over to Metro Moncton, though, and residents are lining up to get their hands on the treated waste produced by the Greater Moncton Sewerage Commission. "We have more demand than we have product," says commission chairman Ron LeBlanc. So what's the difference? LeBlanc says the two regions are not using the same treatment process, resulting in two very different end products. Moncton's treatment process refines the waste down to compost, which is odour-free.

At the treatment plant, the solids are separated from the liquids and lime is added to the solids. "It helps to stabilize the product, it helps with odour control and transportation, and it adds a valuable component to the product when we recycle it back into nature," LeBlanc says. "It's gone from a food product to a waste product to a sludge to what you would call a biosolid. Then we transport it to our composting facility on Delong Drive where we add bark and leaves and different green waste, then we compost it to about 75 degrees Celsius so it kills all the pathogens and bacteria that may be there and renders it safe.

"At the end we have a compost material that is about 10 per cent of the original sludge, once you add in all the other stuff. We call it gardener's gold." And local gardeners certainly seem to be buying into it. LeBlanc says more than 2,000 residents have picked up the compost to date and Moncton, Riverview, and Dieppe have all used it in various areas of the community. LeBlanc says they make about 15,000 tonnes of the compost each year and its use is unrestricted - it can even be used in vegetable gardens.

LeBlanc says there are other areas that do create compost from their sewage waste, "but the site we have is the leading edge in the world, and it is not by accident," he says, explaining the sewerage commission long ago decided to take care of the waste it is responsible for from A to Z rather than off-loading it to private contractors to treat or dumping it in a landfill."

Excerpts from article written by Aloma Jardine published in the Times&Transcript here: http://timestranscript.canadaeast.com/news/article/1180451

I kind of dislike the idea of spreading human poop on my veggie patch, even if it is composted! But I guess the stuff has to go somewhere...