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Ottawa’s two major plants are at Britannia and Lemieux Island, on the Ottawa River. Between them, they flush 545 tonnes of alum-tainted “process waste” – sludge left over after the chemical is used to purify the river water – into the river every year.
In a letter dated Feb. 4, Bryan Dickman, of the Ottawa office of the provincial environment ministry, told the city it had until the end of 2004 to stop flushing alum from the Britannia plant, and until the end of 2006 to stop doing it at Lemieux Island. The city has until this May to present a plan.
But the draft budget tabled Feb. 13 only includes money – $12 million over the next four years – to clean up the city’s act at Britannia. It includes nothing for Lemieux Island, though it does say that the 2006 deadline to clean up the site is “currently under discussion with the Ministry of the Environment.”
“We’ve got to fix the problem,” said Councillor Peter Hume, chairman of the city’s environmental services committee. That committee oversees Ottawa’s water and sewer systems.
City council has known about the problem at least since last September, when city staff presented Mr. Hume’s committee with a report saying that the water plants’ outflows didn’t meet provincial water quality standards.
“We found there was a reduction in the amount of benthic species in the sediment,” said Dixon Weir, the city’s manager of drinking water services, who received a copy of Mr. Dickman’s letter. Benthic species are anything that lives in the bottom of a body of water, from snails to insect larvae.
“The number was reduced, and that indicates there is a problem,” Mr. Weir said. He stressed there was no evidence of damage to fish.
Mr. Hume described the areas as “dead-zone plumes” on the riverbed.
“You look and you find that almost nothing grows there. It’s just dead.”
The study found that the sludge plumes go at least two kilometres downstream. At a point half a kilometre downstream of Lemieux Island, aluminum levels are 39,000-per-cent higher than “background levels.”
Alum is a coagulant that contains aluminum and Mr. Weir said it is used in every water treatment plant. It has chemical properties that make it useful for pulling tiny impurities out of water, such as clay particles.
Mr. Weir said the residue builds up in the treatment plants’ systems. The Britannia plant releases a constant trickle of alum sludge and does a full flushing every six to eight weeks; Lemieux Island uses different technology that backwashes alum out of the plant two or three times a day.
At Lemieux Island, the river is narrower and faster-moving, so the sludge is spread out over a wider area. At Britannia, the river is slower, and more sediment settles over a smaller expanse of riverbed.
“The hard part is figuring out what to do with it,” Mr. Hume said. Mr. Weir said there are four basic options; put it in the sewers so it’s carried to the Robert O. Pickard centre, where all the city’s sewage is processed; haul it to Pickard in trucks; reprocess the sludge to reclaim the alum for reuse; or dry the sludge out and haul the waste away for disposal.
He said dumping it in the sewers would be the cheapest solution, at about $15 million for both plants. Drying the sludge would mean duplicating some of the Pickard centre’s facilities at each treatment plant and would cost a total of about $40 million.
“This is a situation where the least expensive solution probably isn’t the best solution, Mr. Hume said.
For one thing, dumping alum-tainted sludge in the sewers would mean breaking the city’s own bylaws.