Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
October 08, 1998
Human-made wetland to treat village water
The village of Alfred near Ottawa will become one of the first municipalities in Canada to treat wastewater using a constructed wetland.
A one-hectare experimental wetland has been designed by researchers at the University of Guelph's College d'Alfred in conjunction with Stanley Consulting Group Ltd. in Ottawa to treat up to 15 percent of the village's wastewater. The wetland will be operating next spring.
At about one-half the cost of a traditional lagoon system, a constructed wetland is a more environmentally-friendly and economical way to treat wastewater, said Claude Weil, research team leader at the University's College d'Alfred. "This system provides treatment for a much larger volume of water and takes a lot less land than a traditional lagoon system."
The constructed wetland works by digesting organic matter in the wastewater using an "intelligent" shallow lagoon system. It consists of three cells into which wastewater flows in sequence. To mimic natural wetlands, 1,200 cattails and 850 bull rushes were planted in two of the cells, which are shallow ponds .20 metres deep. Seeding also took place in these cells. The third cell, in between the two "wetland" cells, acts as a deeper aerating pond (.6 metres deep).
The cell's configurations and plant species actively reduce levels of nitrogen and pathogenic organisms in the wastewater. Although nitrogen is reduced to acceptable levels through denitrification, reduction of phosphorus is more problematic. To meet stringent requirements for phosphorus levels, adsorption filters will be constructed at the end of the wetland cycle. These filters consist of rechargeable cells of industrial byproducts through which phosphorous adsorption will be monitored.
"Phosphorus is the nutrient of most concern because it promotes the growth of algae which removes oxygen from water as they decay," said Sarah Hurd, an engineering researcher with the project. "This may be the first time these filters are being tested in Canada." Constructed wetland systems are widely used in the United States.
An additional benefit is the natural enhancement of the environment. The constructed wetland will add valuable habitat for a range of animal, bird and fish species, and will complement the village's existing lagoons. Over time, these lagoons have naturally evolved into wetlands that are now nesting sites for rare birds, and are regularly visited by bird watching enthusiasts.
Interest in constructed wetland technology is growing, the researchers added. In addition to the Alfred site, they built wetlands on two dairy operations in eastern Ontario and Quebec.
For more information, contact Claude Weil or Sarah Hurd at College d'Alfred, 613-679-2218, or Communications and Public Affairs at the University of Guelph, 519-824-4120.