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J.P. Antonacci – YourOttawaRegion.com
A mineral named magnetite could be the long-term answer to treating North Grenville’s wastewater.
With continued growth expected in North Grenville’s future, the municipality is looking for an alternative technology to increase capacity and efficiency at the wastewater treatment plant, adjacent to the Ferguson Forest Centre (FFC) in Kemptville.
When magnetite, an iron oxide, is added to a water treatment system, it magnetically attracts large waste particles. The resultant clumps fall out of the water stream, increasing the flow rate and thus the amount of water that can be cleaned per day.
Council recently approved an application to the Ministry of the Environment (MOE) for $125,000 to help fund a Biomag Technology Pilot Program to test the magnetite-based system over two months next spring. If approved, council would be responsible for an additional $125,000.
Though not currently licensed in Canada, Biomag is used in the Boston area and has the potential to make a big difference in North Grenville, said public works Karen Dunlop.
“We can process more water, quicker, and still meet the effluent criteria at the other end of the Rideau River,” she said.
The plant currently uses about half its 4,510 cubic metre daily capacity to treat wastewater from residences and businesses. No storage facility exists to hold excess water, which means on a rainy day – or after several consecutive days of rain – water takes longer to wind its way through the plant, and the potential exists for a backup.
The hope is that the magnetite would keep the system moving even during peak periods, and enable the overall capacity to increase thanks to improved efficiency. This would eliminate the need to use the ten acres of FFC land currently set aside for ponds to hold excess water.
The other bonus to the Biomag system is that magnetite also binds to phosphorous, which means there will be less of the mineral in the cleaned water that ends up back in the Rideau River.
The province has been pushing for lower phosphorus levels in the river, and a future volume increase at the plant would mean acceptable phosphorous levels in the cleaned water would be cut in half.
“You have to have very clean water that enters that stream because you don’t want the oxygen depletion and the algae bloom being created,” Dunlop explained.
It is very expensive to remove phosphorous mechanically. That’s why Dunlop has her fingers crossed that this chemical process would do the trick at a fraction of the cost.
“If we can find a process that takes phosphorous out of the stream that’s cost effective and reasonable, it’ll be a benefit to us,” she said.
If MOE deems the test a success and approves Biomag for use in Ontario, the municipality would need to find $11 million to retrofit the plant with a mixing tank and make additional structural modifications.
Though costly, a mechanical expansion to install a second intake stream, dig the equalization ponds and develop a phosphorus trading system with local farmers would cost even more, between $32 and $37 million according to the municipality’s environmental assessment.
Dunlop thinks the Biomag system could make a lasting difference.
“With our current development proposals, it would be at least 2018 before we would have to consider anything else,” she said.
“So this will get us seven to ten years” before the system reaches capacity at the current growth rate, assuming other water-saving efforts continue.
“I like it. I think that it could be a pretty good silver bullet,” she added.
“It would really be nice if we could remove those equalization ponds completely, and maybe we need a small holding tank for storm flows, rather than 24,000 cubic metres worth of open pond.”
As a bonus, the magnetite itself is magnetically recovered and reused, improving efficiency even further.
Continuing to remove sump pumps and repairing or replacing leaky sewers will further reduce the amount of groundwater entering the system.
“That’s the low-hanging fruit here – tighten up the sewers so (the water) doesn’t even reach the plant,” Dunlop said.
Those tactics, along with water conservation efforts in homes and offices, have already borne fruit.
“Even though we’re expanding and adding people, we’re actually dropping the amount (of water) that we’re treating at the plant, which is fabulous, because it opens up development capacity,” she said.
The municipality’s application has been submitted to the ministry, along with “fabulous” letters of support from MOE, Environment Canada, Rideau Valley Conservation Authority and MPP Steve Clark, Dunlop said.
Results are expected in the fall.