Water is a precious resource and without it life is not possible on earth Water is getting polluted day by day due to excessive and careless use so the percent of available drinking water is reducing There are many ways which causes water pollution and the effects of it are very harmful for all living and non-living objects In general, sewage contains dissolved solids, suspended solids, nutrients (N, P), sulphate, chloride and heavy metals (Fe, Cu, Co, Zn, Pb, Ni), bacteria and viruses. This 0.1% contains organic matter, microorganisms and inorganic compounds. Of the solids present in sewage, 70% are organic and 30% are inorganic in nature. The organic fraction contains proteins (60%), carbohydrates (20%) and fats (10%). The inorganic fraction contains grit, salts and metals. The Sewage Treatment Process essentially includes three stages. What are the three stages of sewage treatment and How does each stage work? The three stages can be divided into primary, secondary, and Tertiary. In each step, water is purified to the next level to access clean water for humans and the environment. 1.This stage essentially includes the process of sedimentation. The water is held in the large sedimentary or rainwater tanks where the settleable solids are removed. Since the sedimentation tanks work on the principle of gravity, the solids settle at the bottom, and the lighter solids float in the tanks. Anyhow, let's move forward to stage 2 of secondary treatment. After the sludge settles at the bottom, the water is then released for its secondary treatment. 2.In this process, waste is broken down by aerobic bacteria and incorporated into the wastewater system.  3. Tertiary treatment is also known as polishing and disinfecting the water with the highest standards. This stage is critical to producing the water to a particular specification such as technical water, mineral water etc. It is also used to treat the water in public systems. 1.the incoming wastewater passes through screening equipment where objects such as rags, wood fragments, plastics, and grease are removed. The material removed is washed and pressed and disposed of in a landfill. The screened wastewater is then pumped to the next step: grit removal. 2. In this step, heavy but fine material such as sand and gravel is removed from the wastewater. This material is also disposed of in a landfill. 3. The material, which will settle, but at a slower rate than step two, is taken out using large circular tanks called clarifiers. The settled material, called primary sludge, is pumped off the bottom and the wastewater exits the tank from the top. Floating debris such as grease is skimmed off the top and sent with the settled material to digesters. 4. In this step, the wastewater receives most of its treatment. Through biological degradation, the pollutants are consumed by microorganisms and transformed into cell tissue, water, and nitrogen.  5. Large circular tanks called secondary clarifiers

1. Presented By
Narendra Kumar Maurya
1st PhD
Dept. of Aquatic Environment Management
College of Fisheries, Mangaluru.

2. What is Waste Water?
 Wastewater is affected by domestic, industrial and commercial use, thus
constantly changing its composition and making it rather difficult to define.
 The composition of wastewater is 99.9% water and the remaining
0.1% is what is removed.

3. Waste Water Treatment
Sewage treatment means removing organic and other oxygen demanding materials such as
suspended solids, nutrients, fats, oil and grease and pathogens from the waste water.
 So that the remaining waste water can be safely returned to the river or sea and become
part of the natural cycle again.
Sewage pollution can be reduced and avoided by the application of various levels of
treatment.
In sewage treatment solids are separated from liquids by physical processes and then the
liquid is purified by biological processes.

4. STAGES OF WASTE WATER TREATMENT
Stage 1: Primary Treatment (Solid Removal)
Stage 2: Secondary Treatment (Bacterial
Decomposition)
Stage 3: Tertiary Treatment (Extra Filtration)

5. WASTE WATER TREATMENT PROCESS

6. PRIMARY TREATMENT
Preliminary treatment
 The major aim of preliminary treatment is to remove the larger solid debris and floating
materials (wood, paper rags and plastics).
 The waste is passed through screens consisting typically of parallel iron bars for the
removal of floating objects (rags, plastics and wood).
 Comminutor’ or macerator is often provided for grinding the coarse material into
smaller particles.
 A separate grit chamber is often provided where the waste is given retention for only a
few minutes to settle down grit and other heavy materials.

7. Primary treatment
 This is a settlement process to remove suspended solids by passing the sewage
through large settlement tanks where most of the solid materials sink to the
bottom by gravity.
 The retention period of wastes in this tank may vary from 90-150 minutes which
results in the removal of about 70% of the solids and 50% of the whole biological
oxygen demand.
 The settled solids are referred as “sludge”.
 The sludge is used on farms after a further treatment called ‘sludge treatment’.

8. SECONDARY TREATMENT
 It is a biological process, which relies on naturally occurring microorganisms
acting to break down organic material and purify the liquid.
 The microorganisms are encouraged to grow on stones over which the sewage
is trickled.
 A film of microbial growth develops on the filtering medium, which may be of
0.2-2.0 mm thick.
 The film consists of bacteria, fungi, protozoa and algae. The process can be
speeded up by blowing air into the sewage tanks.

9. BIOLOGICAL TREATMENT UNIT
 Trickling filters
 Percolating filters
 Activated sludge process
 Aerated lagoons
 Aerobic stabilization ponds
 Rotary biological contractor

10. Trickling filters
 A trickling filter consists of a bed of
graded media such as stones, gravel,
clinker, slag or even synthetic plastic
material, with drains at the bottom to
collect the treated waste.
 The waste is evenly distributed over
the top surface of the bed with the
help of a rotating arm or nozzles,
from where it percolates down in the
filter to the collecting drains

11. In this process, the waste is subjected to
mechanical aeration in specially designed
tanks, which may be rectangular to oval or
circular in shape.
Aeration makes the particles of suspended
matter to flocculate into small gelatinous
masses.
 This gelatinous mass is called “activated
sludge” which is heavily laden with bacteria
followed by protozoans.
Activated sludge process

12.  The flocculate, which develops during aeration is permitted to settle in a
secondary sedimentation tank.
 The added flocculant particles will absorb more suspended and colloidal
matter from the waste.
 The activated sludge treatment is a batch process which usually employs
aeration for a period of 4-10hours before the treated waste can be subjected
to secondary settling.

13. ⮚AWT is a process which is used after conventional treatment.
⮚Tertiary treatment is often used as a synonym for AWT.
⮚It is an additional step after secondary treatment to reduce the suspended solids
and to some extent BOD left in wastewater after primary and secondary
treatment.
⮚It remove mainly soluble pollutant which are not readily removed by
conventional biological treatment.
ADVANCED/ TERTIARY WASTE WATER TREATMENT

14. ⮚For suspended solids:
• Micro screening
• Ultrafiltration
• Chemical coagulation
⮚For dissolved organic matter:
• Adsorption using activated carbon
• Biological oxidation
TYPES OF ADVANCED WASTEWATER TREATMENT
METHODS
⮚For the removal of phosphorus:
• Precipitation
• Coagulation
⮚ For the removal of ammonia:
• Air-stripping
• Biological nitrification

15. ⮚Disinfection:
• Chlorination
• Ozonation
• Ultraviolet radiation
⮚For removal of inorganic nitrogen:
• Denitrification

16. MICROSCREENING
⮚It is a rotating drum either with a plastic filter
fabric or woven metallic mesh having an
opening size of 20 to 60µ attached on its
periphery.
⮚The drum is fitted inside the wastewater flow
channel and it continuously rotates at a speed
of 4 rpm.
⮚The wastewater enters into the horizontal
drum at its upstream end and rotates radially
outward through the mesh or micro fabric
and leaving behind the suspended solid
material which has a diameter greater than
the diameter of mesh.

17. ULTRAFILTRATION
⮚It is a bundle of thin membranes of organic
polymer of about 0.005 to .01 inches thick
that are casted together to act as a single tube
for filtration.
⮚This technique is widely used in conjunction
with the activated sludge process.

18. CHEMICAL COAGULATION
⮚Chemical coagulation is the process of
adding a chemical which can destabilize the
colloidal and suspended particles in the
wastewater.
⮚As a result of destabilization the size of
particles will increase and they settle as floc
due to flocculation and agglomeration.
⮚These settled flocs can be removed using a
sedimentation tank and the supernatant will
be the treated effluent.
⮚Typical coagulants used are natural and
synthetic organic polymers, metal salts such
as Alum, Ferric sulfate etc.

19. BIOLOGICAL OXIDATION
⮚Biological oxidation is the mechanism where
micro organisms degrade organic matter
contaminants of waste water. These micro
organisms feed organic matter in presence of
oxygen and nutrients.
⮚This process is aided by either bacteria or
fungi through their enzymatic activity.

20. ADSORPTION USING ACTIVATED CARBON
⮚Activated carbon, is a form of carbon
processed to have small, low-volume pores
that increase the surface area available for
adsorption or chemical reactions.
⮚Activated carbon is a commonly used
technology based on the adsorption of
contaminants onto the surface of a filter.
⮚ This method is effective in removing certain
organics (micropollutants), chlorine, fluorine
from wastewater.

21. ⮚During water filtration through activated
carbon, contaminants adhere to the surface of
these carbon granules or become trapped in
the small pores of the activated carbon. This
process is called adsorption.

22. CHEMICAL PRECIPITATION
⮚Phosphorus is presented in wastewater is generally seen in the form of organic
phosphate, polyphosphate or orthophosphate.
⮚Chemical precipitation is used to remove the inorganic forms of phosphate by the
addition of a coagulant to wastewater.
⮚This reaction consisting of adding chemicals such as alum, ferric chloride into the
wastewater and they coagulate the phosphorous presented in it.
⮚The coagulated material will precipitate out such as Aluminum phosphate and ferric
and this can be clarified further.

23. AIR STRIPPING
⮚Air stripping is the transferring of volatile
components of a liquid into an air stream.
⮚The conversion ammonium to gaseous phase and
then dispersing the liquid in air, thus allowing
transfer of the ammonia from wastewater to the air.

24. ION EXCHANGE

25. CHLORINATION
⮚By adding chlorine to a wastewater, a stepwise reaction takes place which result in the
conversion of ammonium to nitrogen gas.

26. NITRIFICATION
⮚It is a microbial process by which nitrogen compounds ( primarily ammonia) are
sequentially oxidized to nitrite and nitrate.
⮚The conversion of ammonia to nitrate is performed by nitrifying bacteria.
⮚The nitrification process is primarily accomplished by two groups of autotrophic
nitrifying bacteria.

27. CONTD...

28. DENITRIFICATION
⮚Denitrification is the process where nitrogen is removed from water. It treat the water
to reduce its nitrate content to potable levels.
⮚It is the reduction of nitrates back into the largely inert nitrogen gas, completing the
nitrogen cycle. This is performed in anaerobic conditions.

29. OZONATION
⮚Ozone gas (O3) can be used as a disinfection even though it does not leave a residual in
the water being treated.

30. ULTRAVOILET RADIATION
⮚Involves passing a film of wastewater
within close proximity of a UV source
( lamp).

31. The process of sludge digestion is
carried out by several bacteria
anaerobes, facultative anaerobes and
methanogens.
 Optimum temperature and pH for
anaerobic digestion are 50-600C and
6.8-7.2 respectively.
 Complete digestion requires a time of
about 2-3 weeks.
The sludge still remaining after
digestion may be disposed off either in
water or on land.
The liquid effluent may be given a
tertiary treatment before its final
disposal.
Sludge Digestion

32. • Wastewater treatment and use in agriculture, Natural Resources
Management and Environment Department, FAO corporate document repository.
• Sewage treatment - http://www.fao.org/docrep/t0551e/t0551e05.htm
• http://en.wikipedia.org/wiki/Sewage_treatment
• Aquatic pollution and coastal zone management-cofmelearn.org, ecourse
• ec.europa.eu
• https://engineeringcivil.org
• http://www.brillyantinc.com/index
• http://www.yourarticlelibrary.com/waste-management
• Biology of wastewater treatment- Vol.4,N.F.Gray
REFERENCES

33. Never waste even a drop of water.