Stephenville Wastewater Treatment Facility
The Abydoz Engineered Wetland in Stephenville, Newfoundland was commissioned in 2009-2010. It is the largest subsurface engineered wetland system providing secondary treatment in Canada. Located on the Stephenville airport property, the subsurface flow ensures that the wetland does not attract water fowl or other wildlife that could impact the airport operations.
Design
Population: 7,800 P.E. (Population Equivalent)
Average Flow: 4,555 m3/day
Wetland Treatment Area: 20,000 m2
Inlet Concentration:
95 mg/L BOD
110 mg/L TSS
Outlet Concentration (Ocean Discharge):
40 mg/L BOD
60 mg/L TSS
Process Description
Effluent from the town passes through a spiral screen to remove plastics and non-biodegradable items. Then the flow enters a primary clarifier to settle out suspended solids. From the clarifier the flow is split eight ways and proceeds through the horizontal-flow wetland beds where biological reduction takes place. The flow is then recombined and passes through two vertical beds with final discharge to the ocean.
Sludge treatment cells are located on the other side of the airport. Reed plants dewater and mineralize the sludge from the clarifier, producing a compost-like material. Onsite sludge treatment cells provide significant cost savings by
eliminating expensive sludge transportation and disposal costs.
Actual Treatment Results:
BOD: 78 mg/L reduced to 11.6 mg/L (87% Reduction)
TSS: 177 mg/L reduced to 11.8 mg/L (92% Reduction)
Total Project Cost
$10 Million
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