South Fork Water Treatment Plant

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Contact: Matt Henney

Water supply and treatment facilities can be one of the largest power consumers for municipalities. The City of Nanaimo’s new South Fork Water Treatment Plant is an exception, and a model for sustainability. The City of Nanaimo engaged Associated Engineering to complete pilot testing of treatment options, and provide preliminary design, detailed design and construction services for the preferred option, membrane filtration.

Taking advantage of the hydraulic pressure in the water supply from the South Fork Dam impoundment and the steep topography of the plant site, Associated Engineering’s design team conceived the idea of using a siphon to suction water through the submerged membrane filtration treatment process.  The siphon eliminates mechanical pumping, the typical approach for most treatment plants, significantly reducing energy use.  Using a siphon to draw water through the filters also reduces the building footprint, and capital and operating and maintenance costs. Treating 116 million litres of water per day, the South Fork plant is the largest siphon-powered membrane treatment plant in North America.

Two stages of membrane filtration and clarified backwash recycling increases the overall plant treatment efficiency from 96% to more than 98%, reducing costs for drinking water production.  A constructed wetland treats waste streams from the water treatment process, eliminating the need for onsite mechanical waste treatment equipment or conveying wastes to the distant waste treatment facility.