Wastewater is a (pretty gross) mixture of liquids and solids that residents, businesses and institutions such as schools, flush down the toilets and pour down sinks and drains daily. The slushy mix then travels down the sewer system to one of four wastewater treatment plants in Toronto; The Ashbridges Bay, Highland Creek, Humber or North Toronto wastewater treatment plant (“Wastewater – Water – Services | City of Toronto”, 2014).
Before the actual treatment, the wastewater is passed through a bar screen (a screen with large vertical metal rods) to catch any large objects such as sticks or rocks. After the bar screen, the wastewater is slowed down before entering the grit tank, to give sand, gravel or any other heavy material the chance to settle to the bottom of the tank. All of these objects/debris is sent to the landfill (“Wastewater – Water – Services | City of Toronto”, 2014).
The first ‘treatment’ lets the wastewater sit in settling tank for several hours where eventually the solid particles will sink to the bottom. In the second treatment, a biological process of using micro-organisms helped to clean up the water. Oxygen is added to the water to provide a place for the micro-organisms to grow, these organisms later eat any small bit of organic material/waste (“What happens when I flush?”, 2014)- it’s as if they’re doing all the work for us in this stage! The water is later sent to a ‘clarifier’ where the organisms will settle to the bottom.
When both stages are complete, the water is disinfected with chlorine to be sure any harmful is gone before being released back into Lake Ontario (“Wastewater – Water – Services | City of Toronto”, 2014).
Being being released back into Lake Ontario, the (previously) wastewater must meet some standards:
– The secondary treatment, the process using the organisms + machinery, must remove at least 95 percent of pollutants (James, 2013).