The City of Markham's sanitary sewer system collects and moves domestic/industrial wastewater to the Duffin Creek Wastewater Pollution Control Plant located in Pickering, Ontario.
Once Markham's wastewater reaches the Duffin Creek Wastewater Pollution Control Plant, it goes through an extensive cleaning process. This process includes four general steps.
Step 1: Screening
The first step in wastewater treatment at the Duffin Creek Wastewater Pollution Control Plant is screening. The screening phase removes any large, inorganic objects that may be found in the wastewater. These objects could include things such as rags, diapers, personal hygiene products, and any other inorganic objects that entered the sanitary sewer system along the way to the plant.
Step 2: Primary Treatment
The second step in wastewater treatment at the Duffin Creek Wastewater Pollution Control Plant is primary treatment. Primary treatment removes solid organic matter (also called human waste) from the wastewater. In order to remove this solid organic matter, the treatment plant uses settlement tanks. These settlement tanks work by first allowing the solids to settle to the bottom of the tank, then moving the liquid portion of the wastewater on to secondary treatment.
Step 3: Secondary Treatment
The third step in wastewater treatment at the Duffin Creek Wastewater Pollution Control Plant is secondary treatment. Secondary treatment removes small pieces of organic matter from the wastewater using aeration lanes. These aeration lanes encourage bacteria to eat the tiny bits of solid organic matter that were not removed in primary treatment. Lastly, the partially treated wastewater is moved onto final treatment.
Step 4: Final Treatment
The last step of wastewater treatment at the Duffin Creek Wastewater Pollution Control Plant is final treatment. Final treatment uses a mixture of settlement tanks and sand beds to remove the good bacteria used in secondary treatment. First, the wastewater is placed in a settlement tank to remove the larger clumps of bacteria. Secondly, the wastewater passes through a sand bed, removing almost all of the small clumps of bacteria.
Once the wastewater has passed through the sand bed, it is considered filtered water. All filtered water is discharged into Lake Ontario.