The Lethbridge water treatment plant is attempting to reduce the amount of water it draws from the Oldman River, as well as reduce its overall impact on the environment, Alberta officials announced.
A series of upgrades performed during 2021 now allow the plant to send a portion of its waste stream water to the head of the plant for treatment, recycling as much as 10% of the plant’s flow.
“Waste streams from the treatment process used to be discharged back to the river – we no longer do that,” said Tyler Bennett, water and wastewater engineer for the City of Lethbridge. “It’s all about protecting river quality and the environment. We made changes in a very quick and effective way that’s ultimately led to us having a good handle on the system early on in its operational life cycle,” he added.
MPE Engineering, now part of Englobe, was responsible for the upgrades.
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Bennett noted that waste streams from other stages of treatment, such as filter backwash, are sent to an equalization tank, where they can either be recycled to the head of the water treatment plant or to the wastewater treatment plant.
The water treatment plant is capable of treating as much as 150 million litres of water per day. The water distribution system consists of approximately 590 km of watermain and six storage reservoirs with pump stations.
River water is collected into a raw water well and pumped up to clarifiers to remove particles in the water, measured as turbidity, Bennett explained.
“During clarification the majority of the sediment and particles in the water is removed, and sent to the new residuals system for dewatering,” he said. “This sludge from the clarifiers is the principal waste stream that is treated by the new dewatering facility. The sludge is thickened and pumped through rotary presses to dewater it. When it comes out, up to 1,000 kilograms an hour, it’s a clay-type substance that is ultimately taken to the landfill for disposal.”
Following biosolids treatment upgrades, the local wastewater treatment plant has also been in the process of constructing three new primary clarifiers to replace four existing ones.