The "Green-est" water treatment plant in Canada

Diagram and Building/Area descriptions below:

Stage 1 - Screening

Incoming wastewater passes through an automatically raked bar screen which removes large objects to protect downstream equipment. The screenings are disposed of at the sanitary landfill.

On the right side of the picture you can see the automated raked bar screen. This part of the process is over two stories underground.

Stage 2 - Sewage Pumping Station

Wastewater flows from the City through a network of gravity sanitary sewers to the plant pump station. After screening, variable speed pumps lift the wastewater which then flows by gravity through the various treatment processes. A standby generator provides electrical power to all critical plant process equipment in the event of power failures.

Throughout the treatment process operations are ensured by redundancy in both equipment and design.  Here multiple pumps are available in case of break down.

Stage 3 - Grit Removal

The wastewater flows to aerated grit tanks where sand and gravel are removed. The grit is automatically pumped to an inclined washing and dewatering unit. The liquid portion is returned to the main plant flow and the grit is collected and disposed of at the sanitary landfill.

Stage 4 - Primary Clarification

The flow then enters settling tanks for a detention time of three hours. The larger organic particles settle by gravity to form a dense sludge which is collected and pumped to the anaerobic digester for further treatment.

Stage 5 - Aeration

The effluent from the primary settling tanks flows to the biological treatment stage which is called the "Activated Sludge" Process. This secondary treatment stage is a natural purification process using aerobic micro organisms in the wastewater and oxygen, and is a controlled and balanced biological environment. Large quantities of oxygen and return sludge (from the final clarifiers) are required. The wastewater is retained here for about three hours while the micro organisms consume impurities in the water.

Stage 6 - Final Clarification

The effluent from the aeration tanks called mixed liquor enters the final clarifiers for a detention period of about four hours. The activated sludge settles out, is removed by underwater collection mechanisms, and is pumped back to the aeration tanks to maintain the bacteriological balance. A portion of the sludge that is no longer required for the biological balance in the aeration process is wasted to the primary settling tank and removed with the raw sludge to the anaerobic digester. The final clarifier effluent flows to the receiving waters of Yorkton Creek.

Stage 7 - Sludge Digestion

Raw sludge withdrawn from the primary clarifiers, together with the scum off the top of the primary and final clarifiers, is pumped to the primary anaerobic digester. Here it is mixed continuously and heated to 35 degrees Celsius. This stage provides the necessary environment for anaerobic digestion of sludge, which is the decomposition of organic matter by micro organisms in the absence of air. After a digestion period of 20 days, the sludge flows to the secondary digester. Here the stabilized sludge is thickened. Liquid from the top is returned to the plant. The sludge is then transferred to storage lagoons for further thickening. The sludge is then applied to farm land as a soil conditioner and fertilizer. During the digestion process methane gas is produced. The gas is utilized to fuel boilers and provide heat for the digesters and buildings.

The two sludge digesters are sealed units and are monitored by sensors in the units. Pictured here are the piping and equipment located between the digesters.  They are needed for collecting the methane gas and transporting it from the digesters.

Stage 8 - Plant Operations

The control room provides computer-controlled monitoring of all plant operations and processes. Alarms linked to the computer provide 24 hour alerting to plant personnel of problems that may develop. The laboratory undertakes both routine and specialized analysis for monitoring, process control and reporting of plant operations.

Stage 9 - Chlorination

If wastewater bypasses the treatment process then chlorine is added to the water before entering the receiving waters.