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Calgary has three wastewater treatment facilities:
Together, these treatment plants meet the wastewater and sewage needs of over one million Calgarians each day. We invite you to take the Wastewater Treatment Tour. For detailed descriptions of the recovery process, click through the images in the following diagram and learn more about Wastewater Treatment.
When water runs down a sink, drain or toilet, it becomes wastewater. Calgary has a system just for wastewater that moves it by gravity and pumps it to one of three treatment plants.
Putting fats, grease and oil down the sink can clog your pipes. Objects like dental floss, tissue and rags can lead to sewer back-ups. See a full list of items that can’t go down sinks, drains and toilets.
Pump stations in Calgary move wastewater through the sewer system to the plants.
When wastewater reaches a plant, it passes through screens that remove large materials such as plastic bags, toilet paper, sticks and tennis balls.
The water then travels into grit tanks where heavy items settle to the bottom. We take these materials to one of Calgary's three landfills. From this point, the water flows by gravity to the Primary Clarifiers.
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Water is sent to large open-air tanks called primary clarifiers. It takes about three hours for water to pass through the tanks, and during that time solids settle to the bottom becoming sludge. Oils, grease and fats are skimmed off the top.
The sludge and skimmed waste is pumped to digesters for thickening and decomposition. This is the sludge-handling process. The water from these tanks goes to the Bioreactors.
These large open-air tanks mix in high doses of micro-organisms. The micro-organisms eat nutrients like phosphorus and ammonia, and organic material. After about seven hours, the water flows to the Secondary Clarifiers.
Water enters the secondary clarifiers, where it is held for another seven hours. Micro-organisms settle to the bottom of the tank, where they are recycled back to the Bioreactor.
The cleaner water flows to a weir around the edge of the clarifier and is sent to the Filtration and Disinfection (U.V.) building.
At the Pine Creek plant, treated water flows through cloth-media Disk Filters, improving quality by reducing solids, phosphorus and algae before moving on to disinfection.
Treated water is exposed to ultraviolet light. This light disrupts the micro-organisms' genetic material and makes them unable to reproduce and cause disease.
This kind of disinfection adds no chemicals to the water before returning it to the Bow River.
We return the water to the Bow River. It’s clear, colourless, high in dissolved oxygen, and very low in solids, phosphorus, ammonia, nitrogen and disease causing micro-organisms.
Our laboratories work seven days a week, 365 days a year. We collect samples at all stages of treatment and in the sludge handling program, including Calgro. Our water meets the high standards set by Alberta Environmental Protection.
Sludge from the primary clarifiers passes to gravity thickeners for more settling. This thickens the sludge more before it’s pumped to either the digesters or fermenters.
Sludge sent to the fermenters is thickened and some is used to provide nutrients for the microorganisms in the bioreactors. The remaining sludge is pumped to the digesters.
Sludge enters warm oxygen-less digesters where over 25 days bacteria breaks down complex organic materials into water, methane and carbon dioxide.
The digested sludge, now called biosolids, becomes less smelly and many disease-causing organisms are destroyed. We then pump the biosolids to our Shepard Lagoons.
In the future, we plan to build a de-watering facility that would take some of the biosolids and remove its water, turning it into feedstock for a high quality compost.
We pump biosolids to Shepard Lagoons to thicken. Water that rises to the top of the lagoons is returned to the treatment plants.
Our Calgro program provides biosolids to Calgary farmlands for the growth of crops such as alfalfa, canola, oats, wheat and barley.
Our labs monitor the quality of the Calgro program's biosolids to make sure we meet Alberta Environment's standards.
In 2013, we received approval from Alberta Environment and Sustainable Resource Development (ESRD) to create two demonstration projects for the beneficial use of biosolids.
These projects include fertilizing a willow tree farm and improving soil quality on land that has been deemed not good for growing food.
We are monitoring these projects and the data will be used by The City and the ERSD to develop best practices and guide standards for using biosolids on land. Learn more about the demonstration projects.