February 12, 2010

RURAL GENERATION LTD.

Planting willow tree shoots as part of the preparation for construction of a biomass wastewater treatment facility in Europe. Could a similar plan work in Regina?

FOCUS | Water & wastewater

Regina looks to upgrade wastewater treatment plant

Tree plantation could be part of solution

PETER KENTER

correspondent

The City of Regina has issued an RFP for engineering services to support an upgrade to its wastewater treatment plant.

Until now, the city had been working up to the major plant improvement in stages, concentrating on such smaller projects as a new forcemain and pumping station retrofits.

With a construction budget estimated at $120 to $130 million, this project would represent the most significant investment in wastewater infrastructure in the city’s history.

“The mechanical wastewater treatment plant was built 50 years ago, but isn’t up to the standards of the new federal wastewater guidelines,” says Vicki Campbell, Manager of Wastewater Treatment, City of Regina. “The mechanical plant does a good job of removing solids, biological waste and some nutrients. What we need is a different process to remove more of the nutrients from the wastewater. Nitrogen is the challenge for us with the current technology. We’ll need a massive expansion of some sort, hopefully using the existing facilities as much as possible.”

The effluent is currently sent to wastewater lagoons for final treatment. One novel possibility for treating that effluent involves another type of plant altogether — the common willow tree. The trees are a natural water filter and could thrive on the city’s effluent. The willows could then be harvested, converted to wood chips, and used as fuel in a biomass energy plant built near the plantation.

The concept is the brainchild of Rural Generation Ltd. of Derry, Northern Ireland, a company specializing in waste treatment and energy generation using the fast-growing willows. The company presented its vision after a trip to Regina last year, in co-operation with the Regina Regional Opportunities Commission (RROC), a stakeholder organization that promotes business opportunities in the area.

Claire Kirkland, Director of Strategic Development with RROC, says that the plan could help to cut the cost of wastewater treatment in the city. “Our thinking is that the city could adopt a hybrid approach involving both the current plant upgrade and land-based treatment,” he says. “We’ve established a suitable area of land located 12 kilometres west of the city.”

The operation would involve planting up to 24 million trees on 4,000 acres of land. An acre of willows can treat an estimated two to four million litres of effluent.

The system would require construction of a pipeline or canal to convey the wastewater to the plantation. The effluent would then be surface-irrigated through the plantation by a network of pumps which would ensure even application.

“The other main part of the infrastructure would be the construction of a combined heat and power plant which would be fuelled partly by the plantation and partly by waste wood,” says Chris Johnston, Business Development Manager with Rural Generation. The energy derived from the biomass energy plant could be used to heat local buildings.

One of the challenges of such a project is selecting the right kind of willow trees to do the city’s dirty work. “There are import restrictions in bringing certain cloned material into Canada from Europe,” says Johnston.

“We have been conducting a lot of research with academic institutes in Canada regarding the appropriate clones to use to withstand the specific climate, resist disease and provide the best bio-filtration ability.”

Cloned stock would be inserted into the soil as cuttings using mechanical planters. Willow wood biomass could be ready for harvesting within three to four years of planting.

“The coldest country where willow trees have been used to treat effluent is Sweden, which certainly has warmer winters than Regina, so we’re not certain that willow trees could be used as a year-round solution or not,” says Campbell.

“There’s a lot of investigation that would still need to be done.”

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