By Michael Lynch
The City of Thunder Bay has two water-quality projects that are on the leading edge of technology and innovation. One is brand new, and the other has been in place for several years.
Groundwater under the city's landfill site will soon be protected by fibre-clay and coal clinker, waste by-products from two industrial plants in the city.
"Their waste is our resource," says Darrell Matson, manager, environment division for the city.
"It's like a big rain hat," Matson says of the layers that will cover a cell at the landfill site. Over top of the original garbage in the cell is a 30-centimetre layer of coal clinker. The coal clinker acts as a drainage layer and comes from a coal-fired power plant owned by Ontario Power Corp.
On top of the drainage layer is a 100-centimetre layer of water-tight fibre clay from Provincial Papers, a coated fine-paper mill that utilizes clay in its papermaking process.
A general soil cover 30 centimetres thick is placed over the fibre clay, followed by 15 centimetres of topsoil and grass.
Matson says vent pipes will be placed in the layer for the eventual extraction of methane gas. He says there is a 20 to 30 year supply of methane gas in the cell that can be sold or used to produce electricity through a co-generation agreement.
Thunder Bay's other innovative water quality project is the city's use of a membrane process at its Loch Lommond water treatment plant.
The city owns and operates two water treatment plants that utilize different surface-water sources. In the north end, the Bare Point plant draws from Lake Superior and is a direct filtration plant with dual-media gravity filters. The Loch Lommond plant operates in the south end of the city and is also a direct filtration that employs a membrane process. Both provide a treated product well within provincial and federal guidelines.
Prior to the startup of the membrane process, Loch Lommond’s raw water was being treated solely with screening, chlorination and sodium silicate for corrosion control.
"Although the plant did provide a good product, without the benefit of filtration, there was always the risk of unacceptable water quality," Matson says.
A number of studies were completed to decide on Thunder Bay's water supply. All three concluded that Loch Lommond, as a a source of water supply, be discontinued. As part of the studies, the operation of a pilot membrane plant began at Loch Lommond.
"By coincidence, a giardia lambia cyst was detected in the south end distribution system and a boil water advisory was issued in October 1997," Matson says.
With the success of the pilot membrane plant, and on the recommendation from various consultants, the city chose to install a temporary membrane plant to lift the boil water advisory. The plant was commissioned, and the boil water advisory was lifted in November 1998.
"The membrane plant at Loch Lommond is 99.9999 per cent effective for the removal of particulate matter," Matson says. A membrane pore is 0.5 micron in size, compared to the size of giardia lambia cyst that is 1.5 to two microns in size.
"The technology at Loch Lommond is one of the most advanced in the water industry," says Don Kmill, supervisor of Thunder Bay’s water treatment plants. "We have had visitors from all over the world."
Plans were to move the Loch Lommond membrane plant to the Bare Point facility when it becomes the single source of water for the city. Since the 2000 municipal election, Thunder Bay city councillors have been embroiled in a bitter dispute over whether there should be a single source of water for the city or a dual source.
The most recent estimates from Earth Tech (Canada) have the costs for a dual-source system pegged at $33 million, and single source at $17 million. Two retired engineers, who are members of the city's water advisory committee, say a single source system will cost $35.6 million and a dual-source system will cost $28.8 million.