Wastewater Treatment City of London

What is Wastewater? Water used in our communities and businesses leaves as wastewater to be treated and returned to the environment. All water that is used within the house and goes down a drain. – Toilets, showers, washing machines, sinks, dishwashers, etc. – Industrial, commercial, and institutional waste – What should not be included in wastewater? There is on average 180 ML/day of wastewater treated. 2

Why do we need to treat it? Wastewater can contain a variety of contaminants that can be harmful to the environment, humans and animals. By treating wastewater we can control the spread of water borne diseases. It also keeps our rivers, lakes and ground water clean and healthy. The City of London monitors Thames River health to ensure effluent does not have negative impacts. 3

Greenway Lab Greenway Lab does the tests for all 6 Pollution Control Plants (PCPs) Test are done at varying intervals at Influent, Effluent and Sludge Tests Include: – Biochemical Oxygen Demand – Heavy Metal Testing – Ammonia – Total Phosphorus – Total Kjeldahl Nitrogen (TKN) – Cations – Chloride Nitrate/Nitrite, Sulphate – Oil and Grease – Solids (Volatile Suspended Solids, VSS and Volatile Total Solids, VTS) – Total Coliforms and E. coli – pH 4

Wastewater Operations: Background The City of London has 6 Pollution Control Plants (PCP’s): – Greenway: 1901 – Vauxhall: 1916 – Pottersburg: 1956 – Adelaide: 1958 – Oxford: 1960 – Lambeth: 1963 – Future: Southside Pollution Control Plant Capacity (Cubic Metres per Day) Actual Flow 2012 (Cubic Metres per day) Adelaide36,40023,400 Greenway152,175115,200 Oxford17,2509,000 Pottersburg39,10023,500 Southland Vauxhall20,90014,900 5

Regulations The Ontario Ministry of the Environment regulates more than 470 wastewater treatment plants owned my municipal governments. Wastewater Treatment is regulated under the Ontario Water Resources Act (OWRA) which falls under the Ministry of the Environment. What does it regulate? – Effluent Quality – Reporting Requirements – Effluent sampling and monitoring 6

The System 7

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Step 1: Moving Wastewater to a PCP Raw sewage (seen above) is usually >95% water. Pumping stations and gravity sewers move wastewater to PCPs around the City. 9

As the wastewater enters the PCP it flows through steel screens with 25 mm openings. This removes larger material including: -Paper -Plastic -Leaves -Sticks Step 2: Inlet Works and Coarse Screens The solids removed in the screening process are collected and sent to the landfill. 10

Step 3: Grit Removal Heavier inorganic solids are removed using the vortex system. 11

Step 4: Primary Clarifier Larger organic solids are settling out of the wastewater. These units are designed to allow organic solids to settle out by gravity. The grease forms a scum which is skimmed from the surface of the tanks. 12

Step 5: Aeration Tanks The wastewater is now treated through a biological process to stabilize the dissolved and finely suspended impurities. This is an activated sludge processes and involves the use of bacteria and microscopic organisms. 13

Wastewater during Aeration 14

Step 6: Secondary Treatment (Final Clarifiers) 15

Sludge Collected from Secondary Treatment 16

Step 7: Disinfection 17

Final Effluent 18

Step 8: Sludge Disposal 19

Raw Sludge Sludge from the primary settling tank Centrifuges 20

The Final Effluent Technology is excellent in allowing only minute traces of many substances to be found in the final effluent. We need to be aware that what we put down the drain may make its way back into the environment and possible back into our drinking water. Research shows that these products can remain in wastewater effluent: – Personal Care Products – Estrogen – Sugars – Pharmaceuticals 21

Link to Population Wastewater generation will increase as population increases. In London, the surcharge for wastewater is based on water consumption. 22