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Wastewater Treatment
After studying this PowerPoint presentation you will be able to:-
Understand the need to treat Waste water.
Know about different levels of treatment of waste water.
Learn what happens after the final level of treatment of waste water.
Wastewater –Its Journey to Treatment and Return to the Environment
Where does it all go!
Where does the water from the washer go?
When you flush the toilet where does the contents go?
By gravity flow, the waste is on its way to your local wastewater treatment plant!
Why treat wastewater?
Causes a demand for dissolved oxygen (lower DO levels of streams)
Adds nutrients (nitrate and phosphate) to cause excessive growth
Increases suspended solids or sediments in streams (turbidity increase)
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5
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Park
way
Bowi
e
Wes
tern
Bra
nch
Pisca
taway
Mar
lboro
Mea
dows
Mat
tawom
an
WWTP
mill
ion
gallo
n/da
y
Capacity
Average Flow
The volume of wastewater
PGC 1992 Comprehensive Ten Year Water and Sewerage Plan
Levels of Treatment
Primary Removal by physical separation of grit and
large objects (material to landfill for disposal)
Secondary Aerobic microbiological process (sludge)
organic matter + O2 CO2 + NH3 + H2O
NH3 NO3-
- Lowers suspended solids content (into sludge)
aquatic nutrient
Mostly dead microbes
Aeration and
rapid mixing
Settlingcollects sludge
on bottom
Secondary process
Airdiffuser
From
pri
mary
p
roce
ssTo te
rtiary
pro
cess
Levels of Treatment continuedTertiary (advanced) Anaerobic microbiological process with a
different microbe where O2 is toxic (more sludge)
NO3- N2 (escapes to atmosphere)
PO4-3 if not removed in sludge in secondary
processPO4
-3 + Al+3 AlPO4 (s) (into sludge)
- Aeration to strip N2 and re-oxygenate (add DO)
Slow mixingto keep
suspended and O2 out
Settlingcollects sludge
on bottom
Tertiary processFr
om
seco
ndary
p
roce
ssEffl
uent
Add methanol as food source
When the treatment is done… Effluent back to stream after
A final carbon filtration and Chlorination/dechlorination
Sludge – very nutrient rich Applied directly to land as fertilizer Incinerated (good fuel after drying) Composted