2. What is Wastewater?
• Water is used for many
purposes.
• Water that has been
used and contains
domestic, industrial,
institutional and
commercial waste
products is called
wastewater.
3. Where does wastewater come from?
• Residences (kitchen, bathroom)
• Commercial Institution
• Industrial Institution (usually requires specialized
treatment process)
4. What is wastewater treatment?
• Usually refers to sewage treatment or domestic
wastewater treatment.
• Process of removing contaminants from wastewater,
both run-off and domestic.
5. Goals
• To produce a waste stream.
• To produce solid waste (sludge).
• Then discharge or reuse them back into the
environment.
6. Why do we need to treat wastewater?
• Wastewater treatment is
important to remove
constituents or
contaminants that could
harm people or the
environment.
• Common constituents in
domestic wastewater are:
-Organic Solids
-Nutrients
-Pathogens
7. Where is wastewater treated?
• All sources of
wastewater in a
Sewage Service Area
are connected to
sewers, which join
together to form a
network called a
collection system.
• The collection system
leads to a Water
Pollution Control Plant
(WPCP).
8. How does it get there?
• Water flows downhill
because of gravity, so the
WPCP is usually located
at a low point in the
service area.
• If the force of gravity isn’t
enough, pumping stations
are used to boost
wastewater through
forcemains (pressurized
sewers) to the WPCP.
10. Preliminary Treatment:
• Mechanical screens
remove materials like
rags,
sticks, etc.
• Grit removal processes
remove grit, sand and
granular materials.
11. Primary Treatment:
•Typical materials that are used
during primary treatment include
-fats, oils and greases (a.k.a FOG)
-sand, gravel and rocks
-larger settle-able solids including
human waste
-floating materials
12. Methods used in primary treatment:
Sand catcher Primary sedimentation
14. Methods/Approaches of Secondary
Treatment:
• Secondary treatment is usually accomplished by a
process called suspended growth biological treatment.
• The term “suspended” is used because the biomass
floats freely in the liquid.
• Other approaches are:
-Fixed Film System
-Lagoon System
15. Tertiary Treatment:
•Removal of disease causing organisms from
wastewater.
•3 different disinfection processes:
Chlorination UV light radiation Ozonation
UV light radiation Ozonation
Chlorination
16. Advanced Treatment:
•Quaternary and sometimes tertiary treatment
are classed as advanced treatment.
•Advanced treatment is not always required.
•Technologies include membrane filtration and
reverse osmosis.
18. What is sludge?
• Sludge is solid material
removed from primary
sedimentation tanks and
secondary clarifiers.
• Other sludge components
may include chemical
precipitates and backwash
solids from tertiary filters or
other processes.
19. Sludge Processing - Thickening
• Raw sludge is usually more
than 95% water!
• Thickening the sludge
reduces water and
increases sludge solids
concentration from 3% to
8%.
20. Sludge Processing - Stabilization
• Stabilization is a process that reduces pathogens and sludge
odours.
• Bio-solids are stabilized.
• Biological stabilization is called digestion.
• Aerobic digestion is a suspended growth process with oxygen
present for stabilization.
• Anaerobic digestion involves the decomposition of organic
and inorganic matter in the absence of oxygen.
21. Sludge Processing - Dewatering
• Dewatering reduces the water content of bio-solids to the 20% to 30%
range.
• At this dryness level it is often called sludge cake.
22. Sludge Processing – Bio-solids
• Bio-solids are incorporated
into the soil. Available
nutrients are taken up by
plants for growth.
• If land application is not
possible, bio-solids may be
disposed of in a landfill,
composted or incinerated.
• Further processes exist to
convert bio-solids to a
marketable fertilizer.
23. What can effluent be used for?
•Discharged into a stream, river, bay,
lagoon or wetland.
•Used for the irrigation of a golf course,
green way or park.
•If it's sufficiently clean it can be used for
groundwater recharge.
