Performance Assessment of a Flow Balancing and Wetland Treatment System – Toronto, Ontario


Dunkers2_smallThe Toronto Dunkers Flow Balancing System (DFBS) is located in Bluffers park on the shores of Lake Ontario.  The system incorporates a unique twist to the original concept developed by Karl Dunkers.  Rather than transferring stored water to a treatment plant after a rain event, the water is instead pumped to a ‘sedimentation cell’ separated from the primary storage cells by a berm and solid curtain anchored to the bottom with weights.   From the sedimentation cell, water flows into a wetland cell for final polishing before being released to the lake.  The volume pumped out of the storage cells is replaced by lake water that is pumped into one of the primary cells from Lake Ontario.  Click the image on the right for a schematic showing flow paths through the facility.The Toronto DFBS was monitored intensively in the spring, summer and fall of 2000, 2001 and 2002.  The monitoring program included measurements of flow, rainfall, water quality, water temperature, sediment quality and two dye tests were conducted to asses the hydraulic efficiency of the system.  A multi-year fisheries habitat and vegetation assessment of the wetland area is currently being conducted separately by the Ontario Ministry of Natural Resources.


Despite some operational problems related to the pumps and one of the outlets, the system performed exceptionally well.  Total suspended solids (TSS) were reduced by 81% (based on loads) to a median effluent concentration over the study period of less than 15 mg/L.  Phosphorus, lead copper and zinc witnessed similar declines, with removal rates between 73 and 79% and effluent concentrations generally within acceptable ranges for the protection of receiving waters.

For detailed results on this project, see the report entitled Performance Assessment of a Flow Balancing and Wetland Treatment System – Toronto, Ontario