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Treatments of sewage, sludge and polluted water
1. Mobeen Arshad
Roll no 20
MSc 4th Semester
GC Women University, Sialkot
Treatments of sewage, sludge and
polluted water
2. Contents
i. Sewage
ii. What is sewage treatment?
iii. Process of sewage treatment
iv. Sludge
v. Sludge treatment process
vi. Polluted water
vii. Polluted water treatment
3. Sewage
Produced by a community of people
Characterized by
volume or rate of flow,
physical condition,
chemical and toxic constituents,
Bacteriologic status (which organisms it contains and in
what quantities)
consists mostly of grey water, black water, detergents,
soaps and toilet paper.
4. What is sewage Treatment?
Process of converting sewage water that is no
longer needed or is no longer suitable for use into
bilge water that can be discharged back into
the environment
Sewage water Bilge water
(back into environment)
5. PROCESS OF SEWAGE
TREATMENT
I. SCREENING
removes large objects like, diapers, nappies, sanitary
items, cotton buds, face wipes and even broken bottles,
bottle tops, plastics and rags that may block or damage
equipment.
Special equipment is used to remove grit that gets
washed into the sewer.
II. PRIMARY TREATMENT
separation of organic solid matter (or human waste) from
the wastewater
putting the wastewater into large settlement tanks for the
solids to sink to the bottom of the tank
6. PROCESS OF SEWAGE
TREATMENT
At bottom, large scrappers continuously scrape the
floor of the tank and push the sludge towards the
center.
III. SECONDARY TREATMENT
Put water into large rectangular tanks. called
aeration lanes.
Air pumped into the water to encourage bacteria to
break down the tiny bits of sludge that escaped the
sludge scrapping process.
7. PROCESS OF SEWAGE
TREATMENT
IV. FINAL TREATMENT
treated wastewater is passed through a
settlement tank
Sludge formed at the bottom of the tank from the
settling of the bacteria action
Again sludge scrapped and collected
Free from any harmful substances
Than filtered with a bad of sand
9. SLUDGE
Semi-solid slurry that can be produced from a range of
industrial processes, from water treatment, wastewater
treatment or on site sanitation systems
Settled suspension obtained from conventional
drinking water treatment
Solids separated from suspension in a liquid
10. Sludge treatment Process
Stabilization
Also called mass reduction or degistion
Result in reduction of organic content
Improved drain ability
Reduces odor of the polluted matter
Reduce the volume of sludge
Two units
Anaerobic
aerobic
11. Sludge treatment Process
Aerobic digestion
Organic part decomposes in the presence of
oxygen by micro organism.
Bacteria convert organic matter into carbon dioxide.
• Advantage
Operation is relatively easy
Lower capital cost
Lower BOD concentrations in supernatant liquor
End product odorless and stable
12. Sludge treatment Process
Disadvantage
A high power cost is associated with supplying
the required O2
A digested sludge is produced with poor
mechanical dewatering characteristics
A useful by-product such as methane is not
recovered
13. Sludge treatment Process
Anaerobic digestion
A biological process that uses bacteria in an
oxygen free environment.
These bacteria converts volatile solids into
carbon dioxide, methane and ammonia.
Sludge held without aeration for 10-90 days
Process can be accelerated by heating to 35-
40oC
These are called High Rate Digesters (10-20
days)
14. Sludge treatment Process
Advantages
low solids production
useable methane gas produced
Disadvantages
high capital costs
susceptibility to shocks and overloads
15. Sludge treatment Process
Sludge dewatering
Dewatering aims to reduce the water content
further.
The sludge can then be handled like a solid.
Dewatering can be done mechanically using a
filter
press (employing pressure or vacuum), or a
centrifuge.
Also be done using drying beds.
16. Sludge treatment Process
Drying beds
Most popular methods.
A drying bed consists of a 30 cm bed of sand
with an under-drainage .
Sludge is applied on the sand bed and is allowed
to dry by evaporation and drainage of excess
water over a period of several weeks depending
on climatic conditions.
Bacterial decomposition of the sludge takes place
during the drying process while moisture content
is sufficiently high.
During the rainy season the process may take a
longer time to complete
18. POLLUTED WATER
Water pollution is the contamination of water
bodies (like oceans, seas, lakes, rivers, aquifers
and groundwater) usually caused due to human
activities.
Water pollution is any change in the physical,
chemical or biological properties of water that will
have a detrimental consequence any living
organism.
19. POLLUTED WATER TREATMENT
PROCESS
I. Industrial water treatment
Primary phase
Suspended, solid particles and inorganic material is
removed by the use of filters
Secondary phase
Use biological filters to naturally degrade the organic
waste material
Tertiary phase
All solid particles remove and chemical additives are
supplied to get rid of any left-over impurities
20. POLLUTED WATER TREATMENT
PROCESS
II. De-nitrification
Prevent leaching of nitrates in soil
Fertilizers contain nitrogen, bacteria in the soil
convert the nitrogen in the fertilizer to nitrates,
make easier for plants to absorb
Immobilization is a process where the nitrates
become part of the soil organic matter
Oxygen levels low, another form of bacteria then
turns the nitrates into gases such as nitrogen,
nitrous oxide and nitrogen dioxide
This conversation process called de-nitrification.
21. POLLUTED WATER TREATMENT
PROCESS
III. Septic tanks and sewage treatment
Septic tanks treat sewage at the place where it is
located
Used to treat sewage from an individual building
Untreated sewage from a property flows into the
septic tank
Solids are separated from the liquid, depending
on their density
Heavier particles settle at the bottom of the tank
whereas lighter particles at the top.
Biological process use to degrade solid particles, than
liquid flow in land drainage and solid filttered.
22. POLLUTED WATER TREATMENT
PROCESS
IV. Ozone wastewater treatment
Ozone generator is used to break down
pollutants in the water source
Generators convert oxygen into ozone by using
ultraviolet radiation or by an electric discharge
field
Ozone is a very reactive gas that can oxidise
bacteria, moulds, organic material and other
pollutants found in water
23. POLLUTED WATER TREATMENT
PROCESS
Ozone wastewater treatment benefits:
I. Kills bacteria effectively
II. Oxidises substances such as iron and sulphur
so that they can be filtered out of the solution
III. no nasty odours or residues produced from the
treatment
IV. Ozone converts back into oxygen quickly, and
leaves no trace once it has been used.
24. POLLUTED WATER TREATMENT
PROCESS
Ozone wastewater treatment disadvantage:
I. The treatment requires energy in the form of
electricity; this can cost money and cannot work
when the power is lost.
II. Treatment cannot remove dissolved minerals
and salts.
III. Produce by-products such as bromate that can
harm human health.