Photo courtesy City of Lethbridge.
MPE Engineering, now part of Englobe, recently upgraded a water treatment plant for Lethbridge, Alta., to enhance the quality of water going back into Oldman River.
Through a collaboration with Lethbridge’s municipal government, MPE repurposed several pieces of infrastructure in part of the old plant to implement improved handling of residual waste streams, to align with new provincial regulations from Alberta’s ministry of environment and parks.
The upgraded plant can treat 150 million L of water per day with a multi-step process. It collects water from the river into a well and pumps it up to clarifiers to remove particles.
“Waste streams from the treatment process used to be discharged back to the river,” explains Tyler Bennett, water and wastewater engineer for the city. “We no longer do that. During clarification, the majority of the sediment and particles in the water is removed and sent to a new residuals system. The sludge is thickened and pumped through rotary presses to dewater it. When it comes out at up to 1,000 kg an hour, it’s a clay-type substance, taken to the landfill for disposal. Waste streams from other stages of treatment, such as filter backwash from the filtration process, are sent to an equalization tank, where they can be recycled. By sending a portion of the waste stream water to the head of the plant for treatment, we reduce the water we draw from the Oldman River. We’re allowed by the regulator to recycle up to 10% of our plant flow.”
After undergoing the full treatment process, water enters clearwell storage, is pumped to six storage reservoirs throughout the city and then is pumped into the water distribution network.
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