Sewage Treatment

Sewage Treatment

Where does the wastewater go?

When water goes down your sink or toilet, it travels through small pipes to much larger trunk sewers. The sewer systems are built to the slope of the ground around the Elbow and Bow Rivers. This slope allows most of the waste to go down by gravity, rather than expensive pumps, to one of four plants. To handle low areas, which do not have enough slope, pumping stations have been made.

How is wastewater treated?

Wastewater treatment in Calgary involves the following processes:

Preliminary treatment:

The water flow is slowed down to get the sand, gravel and other materials to settle out into grit tanks. The waste is then strained by bar screens, which remove large solid objects like sticks. All material collected by grit tanks and bar screens is washed and then taken to a landfill.

Primary treatment:

The screened water flows into settling tanks, allowing more solids to settle to the bottom of the tanks. Also at this stage, "scum" (oils and greases) are scraped off the top of the water. This is pumped to large tanks, for disposal.

Secondary treatment:

The half treated water then goes by gravity to covered aeration tanks where it is mixed with "activated sludge" which contains aerobic bacteria. The bacteria eat the organic things remaining in the water. In order to provide a good environment for the bacteria to multiply, air is pumped and spread into the water by blowers. The water, air and ...