Like most municipalities, the City of Saskatoon has two sewer systems:
Storm Sewer System
This system carries rainfall and other surface runoff from parking lots, roads and private properties directly to the South Saskatchewan River. This water is not treated before entering the river. This pipe is large in order to handle great volumes of water that can be produced by major storms.
The Sanitary Sewer System
This system carries wastewater from homes, buildings and industries to the Wastewater Treatment Plant. After being treated, the water is returned to the South Saskatchewan River.
Saskatoon's sanitary sewer system includes more than 850 kilometers of sewer pipes and 58,000 service connections to individual residences, businesses, and industrial sites. These numbers are increasing every year.
Where does wastewater go?
Every time you flush the toilet, take a shower or wash the dishes, you send wastewater down the drain to an underground network of pipes. These pipes, through gravity and a series of pumping stations, carry the wastewater to the Wastewater Treatment Plant.
After the wastewater is treated to ensure it is safe for people and the environment, it re-enters the South Saskatchewan River.
Gravity is the main force of wastewater movement through the system. Pumping is sometimes required to physically lift the wastewater to a higher elevation so it can flow by gravity to the treatment plant. There are 22 pumping stations in Saskatoon.
At the Wastewater Treatment Plant, the wastewater is treated and the remaining liquid, called effluent, is released into the South Saskatchewan River while the biosolids are pumped to a storage site north of the city. The biosolids are a desirable source of fertilizer and liquid injection into farm fields is in high demand.
What causes backups?
When water meant for the larger Storm Sewer flows into the smaller Sanitary Sewer, the Sanitary Sewer can backup (surcharge) and overflow. When this happens, residences are at risk of experiencing sewer backup. Residences located at lower elevations, especially those with inadequate backflow protection, are most at risk.
Another unfortunate side effect is that when storm water goes through the Sanitary Sewer, the Wastewater Treatment Plant is forced to treat it, which drives up overall handling and processing costs. If the Sanitary Sewage System is severely overloaded, untreated sewage may overflow into the river.