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.
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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.
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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:
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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
Wastewater Operations: Background
Pollution Control
City ofPlant
London has
• The
6 Pollution Control
Adelaide
Plants (PCP’s):
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Greenway
Greenway: 1901
Oxford
Vauxhall: 1916
Pottersburg
Pottersburg: 1956
Southland
Adelaide: 1958
Vauxhall
Oxford: 1960
Lambeth: 1963
Future: Southside
Capacity (Cubic
Metres per Day)
Actual Flow 2012
(Cubic Metres per
day)
36,400
23,400
152,175
115,200
17,250
9,000
39,100
23,500
564
258
20,900
14,900
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
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The System
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Step 1: Moving Wastewater to a PCP
Pumping stations and gravity sewers
move wastewater to PCPs around
the City.
Raw sewage (seen above) is usually >95%
water.
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Step 2: Inlet Works and Coarse Screens
As collected
the wastewater
enters
the
PCP it
The solids removed in the screening process are
and sent
to the
landfill.
flows through steel screens with 25
mm openings. This removes larger
material including:
- Paper
- Plastic
- Leaves
- Sticks
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Step 3: Grit Removal
Heavier
inorganic
solids are
removed
using the
vortex
system.
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Step 4: Primary Clarifier
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.
Larger organic solids are settling out
of the wastewater.
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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.
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Wastewater during Aeration
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Step 6: Secondary Treatment (Final Clarifiers)
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Sludge Collected from Secondary
Treatment
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Step 7: Disinfection
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Final Effluent
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Step 8: Sludge Disposal
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Raw Sludge
Sludge from the primary settling
tank
Centrifuges
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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:
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Personal Care Products
Estrogen
Sugars
Pharmaceuticals
Link to Population
• Wastewater generation will increase as
population increases.
• In London, the surcharge for wastewater is
based on water consumption.
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