Sewage plant diverts more waste than ever

Whoever said money is like manure because it does a lot of good if you spread it around might have had a future in sewage treatment.

More solid waste from the Ashbridges Bay Treatment Plant is being directed away from landfills than ever before, largely because it is going to a wider range of users.

About 85 per cent of the solid waste collected at Ashbridges Bay got used in 2012, mostly by farmers who applied it to their southwest Ontario fields as biosolids ‘cake’ or fertilizer pellets.

That means the Ashbridges Bay plant is now putting as much biosolid material to beneficial uses as it once hauled to landfills, said Frank Quarisa, director of wastewater treatment.

“We’re now at the point where the program is well diversified and seems to be self-sustaining,” Quarisa said. “And it’s no longer the significant headache it was for us to manage in 2006.”

It was in 2006 when a Michigan company that had been landfilling 13 to 15 trucks a day of Toronto’s treated sewage decided to quit its contract because nearby residents were complaining about the smell.

That left the City of Toronto scrambling to find new outlets for the stuff which is produced every day of the year, and which totalled some 140,000 wet tonnes in 2012.

Quarisa says a lot of the plant’s current success is thanks to the diversity of its six contractors.

Last year, nearly 40 per cent of the plant’s solid waste was applied directly to farmland as biosolids cake – the most conventional use. But a slightly higher amount went out as fertilizer pellets.

Unlike the cake, which farmers can only apply in early spring and fall when their fields are empty, and which has to follow stricter handling and application rules, the dry pellets can be stored and used year-round.

“It’s a juggling act,” Quarisa said, noting that relying on the conventional cake application alone would mean periods with larger build-ups of material than the plant can store.

Along with the pellet program, which was delayed until 2008 because of a fire during the pelletizer’s construction, Ashbridges Bay has added new contractors, including companies that mix the plant’s biosolids with compost and waste from pulp and paper operations to replace topsoil at mine sites and timber plots.

Quarisa said that by adding new contractors, especially those running the pelletizer operation, the whole biosolids program at Ashbridges Bay is costing the city about $5 million less each year, even as it redirects more waste away from landfills.

In 2009, city councillors set a target to find beneficial uses for 100 per cent of the solid waste at Ashbridges.

Quarisa said that goal remains, though a recent year-long request for new biosolids users only yielded one new company. That company will take a relatively small amount in 2013, about 10,000 tonnes, but hopes to take more next year.

Ashbridges Bay is the largest wastewater treatment plant of its kind in Canada, serving about 1.5 million people.

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corrected comment

BArbara McElgunn
June 21, 2013 • 6:16 pm
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Before any celebration that sewage sludge/biosolids are finding a home in fertilizer via the “beneficial use” program, it would be a good idea to know that hundreds of unregulated, unmeasured, toxic chemical substances, some hormonally active at very blow doses, and pathogens (bacteria, viruses, and parasites) are in that material; and if the practice is sustainable. there are legitimate questions about the safety of food grown on biosolids-treated soil. IT is surprising that spreading untreated chemicals and pathogens on agricultural land would be the preferred way to deal with sewage sludge, when thermal reduction kills all pathogens, and can seriously reduce, or capture, many chemicals of high concern , like dioxin.

In 2002 a report form the US National Academy of Sciences found that EPA’s sludge regulations, that are similar to Ontario’s, may fail to protect the public from infectious diseases. as well as toxic chemicals that cause long-term debilitating illnesses, including cancer. The panel did not address the potential impact of sludge spreading on soil, forests or wildlife, limiting its recommendations to human health. These recommendations include:

Epidemiological studies of the growing number of sludge victims
Testing to identify the full range of toxins and pathogens in sludge
An update of EPA’s antiquated risk assessment of the impacts of sludge on human health
More hazard surveillance and enforcement to protect the public from dangerous sludge practices.
Risk-based standards for land application of biosolids should be re-evaluated on a regular basis to take into account new information regarding the identity and properties of chemicals present in these mixtures and current approaches to evaluating the risks of exposure to such mixtures. Stakeholders should be included in the process, particularly in the development of the exposure assessments.


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